Toward Polyethylene–Polyester Block and Graft Copolymers with

Article pubs.acs.org/Macromolecules

Toward Polyethylene−Polyester Block and Graft Copolymers with Tunable Polarity Szymon Rutkowski,‡ Arkadiusz Zych,‡ Marta Przybysz,‡ Miloud Bouyahyi,† Pawel Sowinski,§ Rolf Koevoets,# Jozef Haponiuk,‡ Robert Graf,∥ Michael Ryan Hansen,∥,⊥ Lidia Jasinska-Walc,*,†,‡ and Rob Duchateau*,† †

SABIC Technology & Innovation, STC Geleen, Urmonderbaan 22, Geleen, The Netherlands Department of Polymer Technology, Chemical Faculty, and §Nuclear Magnetic Resonance Laboratory, Chemical Faculty, Gdansk University of Technology, G. Narutowicza Str. 11/12, 80-233 Gdansk, Poland ∥ Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany ⊥ Institut für Physikalische Chemie, Corrensstr. 28/30, D-48149 Münster, Germany # SABIC Technology & Innovation, Plasticslaan 1, 4612 PX, Bergen op Zoom, The Netherlands ‡

S Supporting Information *

ABSTRACT: The synthesis and characterization of polyethylene−polyester block and graft copolymers and their potential as compatibilizers in polyethylene-based polymer blends are being described. The various routes to functionalized polyethylenes and the corresponding block/graft copolymers have been compared and evaluated for their scalability to industrial scale production. Hydroxyl chain-end and randomly OH-functionalized HDPE as well as randomly OH-functionalized LLDPE were employed as macroinitiators for producing the corresponding block and graft copolymers. These materials were prepared using two different strategies. The graf ting f rom approach entails catalytic ring-opening polymerization of lactones, i.e., ε-caprolactone and ω-pentadecalactone and hydroxyl-functionalized polyethylenes as macroinitiator. The alternative graf ting onto approach involves the preparation of block and graft copolymers via simple and convenient transesterification of polycaprolactone or polypentadecalactone with OH-functionalized polyethylenes. The copolymers were characterized in terms of their molecular weight (SEC), chemical structure (liquid state NMR), topology (MALDI-ToF-MS), supramolecular assembly (solid state NMR), and thermal properties (DSC analysis). The applied techniques for synthesizing the copolymers allow preparation of the products with sufficiently high molecular weight of the final materials. The copolymers were tested as compatibilizers for polyethylene/polycarbonate blends. As proven by SEM analysis, addition of the compatibilizers resulted in a significant improvement of the blend morphology.

■

INTRODUCTION Despite the technological potential and commercial importance of polyolefins,1−6 their apolar character, which reduces the compatibility and adhesion with other materials, limits their application. For example, blends of polyolefins and polar polymers could in principle lead to materials with unprecedented properties that cannot be achieved by either of the independent polymers alone. However, the insufficient interfacial adhesion between polyolefins and virtually any other polymer results in poor mechanical properties of the final products. The adhesion can significantly be improved by the introduction of appropriate interfacial agents. It is known that block and graft copolymers, applied as compatibilizers, locate preferentially at the interface between the two phases, thereby reducing the interfacial tension.7−11 Therefore, block and graft copolymers based on polyolefins and for example polyesters with tunable polarity would be highly desired as compatibilizing agents for a variety of polyolefin-containing blends. The prerequisite is that the different blocks forming the copolymer are identical or at least miscible with the different © XXXX American Chemical Society

phases of the blend. Chain-end or randomly functionalized polyolefins form a crucial ingredient for the synthesis of such compatibilizers. Various interesting reports, concerning polyolefin functionalization, have appeared in the literature. The most common method for producing functionalized polyolefins consists of reactive extrusion.12−16 This process is relatively cheap but has drawbacks like the formation of rather ill-defined products and the occurrence of side reactions such as cross-linking, βscission, and discoloration. Alternatively, well-defined functionalized polyolefins and the corresponding polyolefin-derived graft and block copolymers can be produced applying nonradical postpolymerization17−23 or catalytic approaches.24−29 Based on structural differences, functionalized polyolefins synthesized by catalysis can be divided into several classes, viz. polymers containing randomly Received: October 28, 2016 Revised: December 7, 2016

A

DOI: 10.1021/acs.macromol.6b02341 Macromolecules XXXX, XXX, XXX−XXX

Article

Macromolecules distributed functionalized branches, linear polymers containing randomly distributed functional groups directly attached to the polymer backbone, chain-end-functionalized polyolefins, and polyolefin-derived graft and block copolymers. Several routes lead to polyolefins bearing a terminal functional group, viz. postreactor modification of for example unsaturated chainends,17−23 the use of functionalized chain transfer agents30−36 or functionalized chain stoppers in combination with chain transfer agents,37−39 coordinative chain-transfer polymerization (CCTP)40−50 followed by controlled oxidation,51−57 or olefin metathesis.58−61 Short-chain branched polyolefins containing randomly distributed functionalized branches are typically produced by copolymerization of ethylene and functionalized comonomers.62−82 In the case of comonomers containing nucleophilic functionalities, the latter typically have to be pacified to avoid catalyst deactivation unless appropriate late transition metal catalysts are applied.83−90 Comonomers containing electrophilic functionalities can be used without protection, but in this case the obtained copolymers have to undergo a postpolymerization oxidation treatment to obtain the desired functionality.91−99 Well-defined randomly functionalized PEs, where the functionalities are directly bonded to the main chain, are most effectively produced by acyclic diene metathesis polymerization (ADMET) or ring-opening metathesis polymerization (ROMP) followed by hydrogenation.100−107 Other known approaches toward functionalized polyolefins are anionic living polymerization of dienes, living polymerization of ethylene, or its copolymerization with polar polymers.108−112 These chain-end and randomly functionalized polyolefins can be further used as precursors for the production of block and graft copolymers, which have potential as drug delivery systems or pH- as well as stimuli-responsive materials. In this field Gao et al.110−112 published several papers describing synthesis and characterization of PE-block-polyphosphoester, PE-block-poly(L-glutamate), PE-block-poly(N-isopropylacrylamide), or PEblock-poly(N-isopropylacrylamide)-block-poly(2-vinylpyridine). The sole reports concerning PE-based copolymers, viz. PEblock-PLA113−115 and PE-block-PMMA,116−118 and their use as compatibilizers for polyethylene-containing polymer blends came recently from several research groups. Although PE-blockPCL and PE-graf t-PCL were already published,55,57 their application as compatibilizers for e.g. PE/PC blends has not been reported. Polyolefin-based block and graft copolymers can be produced using different strategies. The graf ting f rom approach starting from functionalized polyolefins is most commonly reported (Scheme 1). Radical, ionic, and catalytic ring-opening polymerization are the most prevalent polymerization methods used.17,18,28,29,31,55,56,59,119−129 The alternative, graf ting onto approach is infrequently applied. The combination of secondorder kinetics and the low concentration of coreactive groups (typically chain ends and the functionalities at the polyolefins) results in low conversions and long reaction times.130,131 Transesterification of a polyester in the presence of a hydroxylfunctionalized polyolefin forms an exception on this rule (Scheme 1).132 Since the concentration of ester functionalities does not change during the reaction, this graf ting onto process follows first-order kinetics guaranteeing a much high conversion and shorter reaction times than a second-order reaction. For this reason and for its simplicity, this method will be investigated here as well.

Scheme 1. Grafting Onto and Grafting From Approach toward Polyethylene-block-polyester Copolymers

Herein, we describe and compare several approaches to produce hydroxyl-functionalized polyethylenes and polyethylene−polyester block and graft copolymers and the use of these block and graft copolymers as compatibilizers in PE/PC blends. This study emphasizes comparing the practicality and scalability of the different methodologies to an industrial scale. Processes that are very successful at the lab scale can be impractical on the commercial scalean important issue that is often overlooked.

■

EXPERIMENTAL SECTION

Materials. ω-Pentadecalactone (PDL) (98%, Sigma-Aldrich), εcaprolactone (CL) (97%, Sigma-Aldrich), and benzyl alcohol (BnOH) (99%, Merck) were dried over CaH2 (95%, Sigma-Aldrich) and distilled under reduced pressure. Cyclooctene (95%, Sigma-Aldrich), 5-hydroxycyclooctene (97%, Carbosynth), benzylidenebis(tricyclohexylphosphine)dichlororuthenium (second-generation Grubbs ruthenium catalyst, Sigma-Aldrich), tris(triphenylphosphine)rhodium chloride (Wilkinson catalyst, Sigma-Aldrich), 1-octene (98%, SigmaAldrich), ethyl vinyl ether (98%, Fluka), N,N′-bis(salicylidene)ethylenediamine (98%, Sigma-Aldrich), N,N′-bis(salicylidene)-2,2dimethyl-1,3-propanediamine (98%, Sigma-Aldrich), OH07 Yparex (HDPE-graf t-MAH, Yparex), 2-aminoethanol (99%, Sigma-Aldrich), and tin(II) 2-ethylhexanoate (92−100%, Sigma-Aldrich, Sn(Oct)2) were used as received. Dry ethanol (Biosolve) was used as received. Tetrahydrofuran and toluene (Sigma-Aldrich) were dried using an MBraun-SPS-800 purification column system. Dry, oxygen-free pentamethylheptane (PMH) was employed as solvent for ethylene polymerization experiments. 10-Undecene-1-ol was purchased from Sigma-Aldrich and dried with 4 Å molecular sieves under an inert atmosphere. Methylaluminoxane (MAO, 30 wt % solution in toluene) was purchased from Chemtura. Diethylzinc (1.0 M solution in hexanes), trimethylaluminum (2.0 M solution in toluene), and triisobutylaluminum (1.0 M solution in hexanes) were purchased from Sigma-Aldrich. rac-Me2Si(Ind)2ZrCl2 was purchased from MCAT GmbH, Konstanz, Germany. [Et2NC(NCy)2]TiCl3 was prepared following literature procedures.55 Synthesis of Aluminum−Salen Complex 1. 133 N,N′-Bis(salicylidene)ethylenediamine (2.0 g, 7.5 mmol) was suspended in toluene (30 mL) under N2 flow. Subsequently, Al(CH3)3 (2 M solution in toluene, 3.75 mL, 7.5 mmol) was added via syringe, and the mixture was stirred at room temperature for 1 h. The thus obtained solution was concentrated to half the original volume, and pale yellow needles of 1 were isolated with a yield of 93%. Synthesis of Aluminum−Salpen Type Complex 2.133 N,N′Bis(salicylidene)-2,2-dimethyl-1,3-propanediamine (2.0 g, 5.7 mmol) was suspended in toluene (30 mL) under N2 flow. Subsequently, Al(CH3)3 (2 M solution in toluene, 2.85 mL, 5.7 mmol) was added via B


Article

Macromolecules

with a screw rotation speed of 100 rpm. To form N-(2-hydroxyethyl)succinimide attached to the PE backbone, maleic anhydride-functionalized HDPE (Yparex OH07, 10 g) with Irganox B225 (2500 ppm) was fed into the extruder, and after a few minutes 2-aminoethanol (0.28 g, 4.6 mmol) was added via syringe. The mixture was processed, and then the extruder chamber was evacuated. The hydroxylfunctionalized polyethylene was purified by dissolution in m-xylene at 120 °C and precipitated in cold acetone. Typical Procedure for the Synthesis of Randomly HydroxylFunctionalized HDPE, HDPE-OHn, via ROMP Followed by Hydrogenation. A mixture of cis-cyclooctene (5.0 g, 45.5 mmol) and 5hydroxy-cis-cyclooctene (172 mg, 1.36 mmol), second-generation Grubbs catalyst (19.3 mg, 22.7 μmol), and toluene (10.0 mL) were stirred at room temperature for 24 h. The manipulations were carried out in the glovebox. Ethyl vinyl ether (1.7 mg, 22.7 μmol) was added to quench the polymerization after which the polymer was precipitated in acidified methanol. The unsaturated polymer was dissolved in toluene and transferred to a 300 mL stainless steel Büchi reactor. Subsequently, an appropriate amount of Wilkinson catalyst dissolved in toluene (2 mL) was added via syringe, and the mixture was stirred for 48 h at 90 °C under H2 (20 bar). Afterward, the reaction mixture was quenched in acidified methanol, filtered, and purified by reprecipitation in methanol. The saturated polymer, HDPE-OHn, obtained in 94% yield, was dried under reduced pressure at 80 °C for 24 h (for the reaction scheme and 1H NMR spectra see Figures S4 and S5). Typical Procedure for the Synthesis of HDPE-block-PPDL Copolymers via Catalytic Ring-Opening Polymerization. In a glovebox a glass crimp cap vial was charged with toluene (1.5 mL), PDL (1.0 g, 4.5 mmol), HDPE-OH (13 mg, 8.7 μmol), and catalyst 1 (3 mg, 8.7 μmol). Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. A similar procedure was applied for the synthesis of HDPE-blockPCL copolymers. In the glovebox a glass crimp cap vial was charged with toluene (1.5 mL), CL (0.513 g, 4.5 mmol), HDPE-OH (13 mg, 8.7 μmol), and catalyst 1 (3 mg, 8.7 μmol). Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. Typical Procedure for the Synthesis of HDPE-graf t-PPDL Copolymers via Catalytic Ring-Opening Polymerization. A glass crimp cap vial was charged with PDL (1.15 g, 4.8 mmol) and catalyst 1 (3 mg, 8.7 μmol), HDPE-OHn (70 mg, 8.7 μmol), and toluene (1.50 g, 16.3 mmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. A similar procedure was applied for the synthesis of HDPE-graftPCL copolymers. A glass crimp cap vial was charged with CL (0.547 g, 4.8 mmol) and catalyst 1 (3 mg, 8.7 μmol), HDPE-OHn (70 mg, 8.7 μmol), and toluene (1.50 g, 16.3 mmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. Typical Procedure for the Synthesis of LLDPE-graf t-PPDL Copolymers via Catalytic Ring-Opening Polymerization. A glass crimp cap vial was charged with PDL (1.15 g, 4.8 mmol) and catalyst 2 (1.68 mg, 5 μmol), LLDPE-OHn (44.1 mg, 5 μmol), and toluene (1.50

syringe, and the mixture was stirred at room temperature for 1 h. The thus-obtained solution was concentrated to half the original volume, and pale yellow crystals of 2 were isolated with a yield of 88%. Typical Hydroboration/Oxidation Procedure for the Synthesis of Chain-End Hydroxyl-Functionalized Polyethylene, HDPE-OH. The hydroxyl end-capped polyethylene was prepared applying the hydroboration/oxidation procedure described in the literature.98 The procedure for producing 100% vinyl-terminated low molecular weight polyethylenes was reported by Liciulli et al. using a chromium catalyst system.134 Under a nitrogen atmosphere, a 100 mL glass reactor was charged successively with a mixture of toluene/THF (60:20 mL) and the predried vinyl-terminated PE (2 g). The mixture was stirred and kept at 60 °C for 30 min. To the stirred suspension, the solution of 9BBN in THF (0.5 M) was added dropwise by syringe (6 mL). The reaction mixture was stirred at 60 °C for 6 h under a nitrogen atmosphere. After cooling the mixture to room temperature, the aqueous solution of NaOH/H2O2 (3 mL of 35 wt % solution in THF) was added dropwise, and the mixture was stirred and kept at 40 °C for 6 h. After the oxidation step, the dispersion was poured into methanol, and the precipitated powder was filtered. The powder was washed in refluxed methanol for 2 h, filtered, and dried under reduced pressure at 60 °C for 24 h. 1H NMR demonstrated that 95+% of the polymers were chain-end hydroxyl-functionalized (Figure S1). Typical Procedure for the Synthesis of Chain-End HydroxylFunctionalized Polyethylene, HDPE-OH, by CCTP (Table 1, Entry 4). Polymerization reaction was carried out in a stainless steel Büchi reactor (300 mL). Prior to the polymerization, the reactor was dried in vacuo at 40 °C and flushed with nitrogen. Toluene (60 mL) and MAO (30 wt % solution in toluene, 0.25 mL) were added and stirred at 50 rpm for 20−30 min. TiBA (1.0 M solution in hexanes, 2 mL) and DEZ (1.0 M solution in hexanes, 0.5 mL), were added, the solution was saturated with ethylene and stirred for 10 min. In a glovebox, [Et2NC(NCy)2]TiCl3 (3) (3.0 mg) was dissolved in toluene (ca. 3 mL) and transferred into the reactor. The reactor was then pressurized to the desired pressure with ethylene (2 bar), and the pressure was maintained for a predefined time. At the end of polymerization, the ethylene feed was stopped and after releasing the residual ethylene pressure, dry synthetic air was added through a gas injection tube, and the suspension was kept under constant pressure at 60 °C for 2 h with rigorous stirring (600 rpm) before being quenched with 300 mL of acidified methanol (2.5 wt % of concentrated HCl). The resulting white powder was then filtered, washed with methanol, and dried at 60 °C under reduced pressure in a vacuum oven at 60 °C for 24 h. 1H NMR revealed that 80% of the product consisted of HDPE-OH (Figure S2 and Table 1, entry 4). Typical Procedure for the Synthesis of Randomly HydroxylFunctionalized Polyethylene, LLDPE-OHn (Table 1, Entry 6). Copolymerization reactions of ethylene and aluminum-pacified 10undecen-1-ol (Al:C11OH = 1) were carried out in a stainless steel Büchi reactor (300 mL). Prior to the polymerization, the reactor was dried in vacuo at 40 °C and flushed with nitrogen. PMH solvent (90 mL) was introduced followed by MAO (30 wt % solution in toluene, 0.22 mL). The resulting mixture was stirred for 15−20 min followed by the injection of the premixed solution of 10-undecen-1-ol (C11OH) and TiBA (1.0 M solution in toluene, 2.5 mL, TiBA/C11OH = 1) under a nitrogen atmosphere. The solution was saturated with ethylene (1 bar) and stirred for 10 min. The polymerization reaction was started by the injection of a solution of rac-Me2Si(Ind)2ZrCl2 catalyst 4 (2.3 mg dissolved in 3 mL of toluene). The reactor was then pressurized to the desired pressure with ethylene (2 bar), and the pressure was maintained constant for 10 min. At the end of the reaction, the ethylene feed was stopped, and the resulting mixture was poured into acidified methanol (2.5 wt % of concentrated HCl) and stirred for 2 h. The suspension was then filtered, and the polymer powder was dried under reduced pressure in a vacuum oven at 60 °C for 24 h. 1H NMR demonstrated that the average comonomer incorporation levels 1.3 mol % (Figure S3 and Table 1, entry 6). Typical Procedure for Synthesis of Randomly Hydroxyl-Functionalized Polyethylene, PE-OHn, by Reactive Extrusion. The experiments were carried out in a corotating twin-screw mini-extruder at 150 °C C


Article

Macromolecules

Size exclusion chromatography (SEC) was performed at 160 °C on a Polymer Laboratories PLXT-20 Rapid GPC Polymer Analysis System (refractive index detector and viscosity detector) with three PLgel Olexis (300 × 7.5 mm, Polymer Laboratories) columns in series. 1,2,4-Trichlorobenzene (TCB) was used as eluent at a flow rate of 1 mL min−1. The molecular weights were calculated with respect to polyethylene standards (Polymer Laboratories). A Polymer Laboratories PL XT-220 robotic sample handling system was used as autosampler. MALDI-ToF-MS analysis was performed on a Voyager DE-STR from Applied Biosystems equipped with a 337 nm nitrogen laser. An accelerating voltage of 25 kV was applied. Mass spectra of 1000 shots were accumulated. The polymer samples were dissolved in CHCl3 at a concentration of 1−3 mg mL−1. The cationization agent used was potassium trifluoroacetate or sodium trifluoroacetate (Fluka, >99%) dissolved in THF at a concentration of 5 mg mL−1. The matrix used was trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) (Fluka) and dissolved in THF at a concentration of 40 mg mL−1. Solutions of matrix, salt, and polymer were mixed in a volume ratio of 4:1:4, respectively. The mixed solution was hand-spotted on a stainless steel MALDI target and left to dry. The spectra were recorded in the reflection mode. All MALDI-ToFMS spectra were recorded from the crude products. Melting (Tm) and crystallization (Tc) temperatures as well as enthalpies of the transitions were measured by differential scanning calorimetry (DSC) using a DSC Q100 from TA Instruments. The measurements were carried out at a heating and cooling rate of 10 °C min−1 from −60 to 160 °C. The transitions were deduced from the second heating and cooling curves. Variable-temperature (VT) solid-state 13C{1H} cross-polarization/ magic-angle spinning (CP/MAS) NMR and 13C{1H} insensitive nuclei enhanced by polarization transfer (INEPT) magic angle spinning (MAS) experiments were carried out on a Bruker AVANCE III 500 spectrometer employing a double-resonance H-X probe for rotors with 4.0 mm outside diameter. These experiments utilized a MAS frequency of 10.0 kHz, a 5.0 μs π/2 pulse for 1H and 13C, a CP contact time of 2.0 ms, and SWf-TPPM decoupling during acquisition.135 The CP conditions were preoptimized using L-alanine. The 13C{1H} INEPT MAS NMR spectra were recorded using the refocused-INEPT sequence with a J-evolution period of either 1/(3JCH) or 1/ (6JCH).136−138 The VT 13C{1H} CP/MAS and 13C{1H} INEPT MAS NMR spectra were recorded under isothermal conditions at selected temperatures. A heating rate of 2 °C/min was employed between temperatures. Reported temperatures are corrected for friction-induced heating due to spinning using 207Pb MAS NMR of Pb(NO3)2 as an NMR thermometer.139,140 Chemical shifts for 1H and 13 C are reported relative to TMS using solid adamantane as an external.141 SEM analysis of the freeze fractured samples were performed using a HITACHI SU8010 apparatus equipped with cold cathode fieldemission source. The samples were sputter-coated using Cressington Sputter Coater 108Auto with Au. Tensile tests were performed with a Zwick type Z020 tensile tester equipped with a 20 kN load cell. The tests were performed on injection molded samples having the dimensions of 75 mm × 4 mm × 2 mm. A grip-to-grip separation of 50 mm was used. The samples were prestressed to 3 N and then loaded with a constant cross-head speed 50 mm/min. Izod impact strength was measured using a Zwick/Roell HIT5.5P tester according to ISO 180-2001. The dimensions of the injectionmolded sample bars without notch were 60 mm × 10 mm × 4 mm. For each sample the average value reported was derived for at least five specimens. The testing was carried out at room temperature (25 °C). The water contact angles were measured by putting sessile drops of the liquid on the samples and monitoring the drop shape, using by contact angle goniometer DataPhysics OCA 20 Instrument at a temperature of 23 °C. Sessile drops (1 μL) of a distilled water were used for the advancing contact angle measurements. The ellipse method was used for extraction of the drop profile.

g, 16.3 mmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. A similar procedure was applied for the synthesis of LLDPE-graftPCL copolymers. A glass crimp cap vial was charged with CL (0.547 g, 4.8 mmol) and catalyst 2 (1.68 mg, 5 μmol), LLDPE-OHn (44.1 mg, 5 μmol), and toluene (1.50 g, 16.3 mmol). All manipulations were carried out in the glovebox. Then, the mixture was removed from the glovebox and stirred in an oil bath at 100 °C. The progress of the reaction was followed by 1H NMR spectroscopy by taking aliquots at set time intervals. The synthesized copolymer was cooled to room temperature and quenched using acidified methanol, isolated, and dried under vacuum at room temperature for 18 h. Typical Procedure for the Synthesis of PE-graf t-PCL Copolymers via Transesterification. Hydroxyl-functionalized PE-OHn (8.0 g, Mn = 12.6 kg mol−1, ĐM = 3.2, obtained by reactive extrusion of Yparex OH07 with ethanolamine) and PCL (2.0 g, Mn = 25.6 kg mol−1, ĐM = 1.3) were fed into a corotating twin-screw mini-extruder at 150 °C with a screw rotation speed of 100 rpm. The polymers were premixed for 5 min. Then the catalyst Sn(Oct)2 (0.19 g, 0.5 mmol) was added, and the mixture was stirred in the extruder for 2 min. After this time the extruder was evacuated. The copolymer was purified by dissolution in m-xylene at 120 °C and precipitation in cold acetone. The copolymer was dried in a vacuum oven for 48 h at room temperature. Typical Procedure for the Preparation of LDPE/PC Blends. 8.0 g of LDPE (LDPE2801, MFR = 0.55 g/10 min (190 °C/2.16 kg)) and 2.0 g of PC (PC115, MFR = 15 g/10 min (300 °C/1.2 kg)) were fed into a corotating twin-screw mini-extruder. The mixture was processed at 230 °C for 5 min with a screw rotation rate set at 100 rpm. The blends were investigated in terms of their morphology, static mechanical properties, and surface properties. Typical Procedure for Preparation of LDPE/PC Blends Compatibilized by HDPE-graf t-PCL Copolymer. 8.0 g of LDPE (LDPE2801, MFR = 0.55 g/10 min (190 °C/2.16 kg)), 2 g of PC (PC115, MFR = 15 g/10 min (300 °C/1.2 kg)), and 0.5 g of HDPE-block-PCL were fed into a corotating twin-screw mini-extruder. The mixture was processed at 230 °C for 5 min with a screw rotation rate set at 100 rpm. The blends were investigated in terms of their morphology, static mechanical properties, and surface properties. Typical Procedure for Preparation of HDPE/PC Blends. 8.0 g of HDPE (HDPE CC253, MFR = 1.8 g/10 min (190 °C/2.16 kg)) and 2.0 g of PC (PC115, MFR = 15 g/10 min (300 °C/1.2 kg)) were fed into a corotating twin-screw mini-extruder. The mixture was processed at 230 °C for 5 min with a screw rotation rate set at 100 rpm. The blend was investigated in terms of its morphology, static mechanical properties, and surface properties. Typical Procedure for Preparation of HDPE/PC Blends Compatibilized by HDPE-graf t-PCL Copolymer. 8.0 g of HDPE (HDPE CC253, MFR = 1.8 g/10 min (190 °C/2.16 kg), 2 g of PC (PC115, MFR = 15 g/10 min (300 °C/1.2 kg), and 0.5 g of HDPE-block-PCL were fed into a corotating twin-screw mini-extruder. The mixture was processed at 230 °C for 5 min with a screw rotation rate set at 100 rpm. The blend was investigated in terms of its morphology, static mechanical properties, and surface properties. Measurements. 1H NMR analysis carried out at 80−110 °C using deuterated tetrachloroethane (TCE-d2) as the solvent and recorded in 5 mm tubes on a Varian Mercury spectrometer operating at frequencies of 400 MHz. Chemical shifts are reported in ppm versus tetramethylsilane and were determined by reference to the residual solvent. Heteronuclear multiple-bond correlation spectra (HMBC) were recorded with pulse field gradients. The spectral windows for 1H and 13 C axes were 6075.3 and 21 367.4 Hz, respectively. The data were collected in a 2560 × 210 matrix and processed in a 1K × 1K matrix. The spectra were recorded with the acquisition time 0.211 s, relaxation delay 1.4 s, and number of scans equal to 144 × 210 increments. D


Article

Macromolecules

Table 1. Coordinative Chain Transfer Polymerization of Ethylene Catalyzed by 3a and Ethylene/10-Undecen-1-ol (C11OH) Copolymerization Catalyzed by 4b CTA/cat. entry f

1 2 3 4 5f 6f 7

cat. 3 3 3 3 4 4 4

C11OH/cat.

TIBA [equiv]

400 400

DEZ [equiv]

time [min]

yieldc [g]

Mnd [g mol−1]

ĐM d

branchese [mol %]

5 30 5 30 10 10 10

2.9 7.4 2.0 7.2 5.1 2.5 0

3200 4500 1300 2230 23300 9200

2.0 1.8 1.4 2.1 2.6 2.1

n.a n.a n.a n.a n.a 1.3 n.a

100 100

500 1000

Conditions: catalyst (3) = 5 μmol, molar ratio Al(MAO)/Ti = 2250, ethylene pressure 2 bar, reaction temperature 40 °C, toluene = 60 mL. Conditions: catalyst (4) = 5 μmol, 10-undecen-1-ol pretreated with TiBA (TiBA:C11OH = 1 equiv), molar ratio Al (MAO)/Zr = 2000, ethylene pressure 2 bar, reaction temperature 40 °C, PMH 90 mL. cYield is the weight of polymer powder obtained after filtration and drying in a vacuum oven for 24 h at 60 °C. dExperimental number-average molecular weight and molecular weight distribution determined by HT-SEC in TCB at 160 °C. eRefers to the percentage of C11OH calculated from 1H NMR spectra. fMelting temperatures as determined by DSC, entry 1 (Tm = 131 °C), entry 5 (Tm = 132 °C), and entry 6 (Tm = 119 °C). a b

■

RESULTS AND DISCUSSION Hydroxyl-Functionalized Polyethylenes. Two different routes toward chain-end hydroxyl-functionalized polyethylenes have been investigated and compared. The first approach consists of postpolymerization functionalization of a vinylterminated polyethylene by means of hydroboration followed by oxidation.17,18 The second route involves an in-reactor functionalization process using main group metal alkyls as chain transfer agents in a coordination chain transfer polymerization (CCTP) process followed by oxidation.40−57 Vinyl-terminated polyethylenes are readily produced by several catalyst systems, including the commercial Phillips catalyst and many single-site catalysts. The disadvantage is that the postpolymerization functionalization of these polymers requires solubilizing the materials, and the low concentration of the terminal double bonds dramatically limits the efficiency of the subsequent chemical transformation step into the desired chain-end functional group. To reduce this limiting effect for this study, low molecular weight vinyl-terminated HDPE, produced using the highly active chromium catalyst Me3CCH2N(2-Py)CrCl3(THF),134 was treated with 9-borabicyclo[3.3.1] nonane (9-BBN), followed by oxidation with H2O2/NaOH. The oxidation process was virtually quantitative. Due to both low solubility and low concentration of reactive vinyl groups for high molecular weight polymers, this technique is limited to low molecular weight polyethylenes. While useful on lab scale, this postpolymerization functionalization method is less practical and expensive on an industrial scale of production. In the second approach, the functionalization forms part of the polymerization process, and treatment of the CCTP product with oxygen followed by hydrolysis readily affords the chain-end hydroxyl-functionalized polyolefin.51−57 Literature data showed so far that generally rather low molecular weight products are formed unless the chain transfer is reversible, which typically requires the polymerization to be performed in a solution process, which as a result of viscosity issues also limits the obtainable molecular weight of the product. To produce chain-end hydroxyl-functionalized HDPE in the reactor by catalysis, a titanium guanidinate catalyst [Et2NC(NCy)2]TiCl3 (3) activated with MAO was used, which in the presence of TiBA and a small amount of diethylzinc provided a ternary CCTP system effectively producing metal-terminated HDPE (metal = Al, Zn). To produce hydroxyl-terminated polyethylene (HDPE-OH), the metal-terminated polyethylene

was in situ oxidized using synthetic air followed by acidic workup (Table 1, entries 3 and 4). The 1H NMR spectrum of HDPE-OH displays the characteristic resonance at 3.67 ppm assignable to α-methylene protons next to the OH end-group. Integration of the α-CH2 and CH3 resonances revealed that around 80% of the product consisted of HDPE-OH, the rest being unfunctionalized saturated HDPE (Figure S2). Varying the oxidation conditions (i.e., temperature, pressure, time) did not lead to a significant increase in the functionalization efficiency. CCTP as a process is being applied commercially for example for the production of olefinic block copolymers.48 Hence, using this approach for producing chain-end-functionalized PE is more likely to be economically feasible on commercial scale than hydroboration. However, oxidation by air introduces safety risks. To produce LLDPE with hydroxyl-functionalized branches, catalyst 4 has been evaluated in ethylene copolymerization with TiBA-pacified 10-undecene-1-ol (TiBA:C11OH = 1) as the functional comonomer under the conditions displayed in Table 1. As expected, the catalytic performance of 4 varies according to the reaction conditions, but the activity was mainly affected by the amount of the functional monomer present. Despite the pacification of the hydroxyl functionality, the addition of polar comonomer ([C11OH]:[cat.] = 500) resulted in a decrease in the catalytic activity, which dropped further with increasing the concentration of C11OH in the feed (entries 5−7, Table 1). For [C11OH]:[cat] ratios above 500, complete deactivation of 4 was observed. As demonstrated by 1H NMR analysis, the average comonomer incorporation obtained using catalysts 4/ MAO levels at 1.3 mol % (Figure S3 and Table 1, entry 6). Alternatively, to prepare unbranched HDPE’s, having randomly distributed hydroxyl functionalities along the polymer backbone, ring-opening metathesis polymerizations (ROMP, see Figures S4 and S5) of mixtures of cis-cyclooctene and 5hydroxy-cis-cyclooctene have been performed.100−118 The reactions were catalyzed using a second-generation Grubbs catalyst, followed by hydrogenation using the Wilkinson catalyst. This approach allows the formation of so-called precision polyolefins, providing a copolymer resembling EVOH (ethylene−vinyl alcohol copolymer) with tunable hydroxyl groups content and a linear polymer structure. The concentration of hydroxyl groups can easily be tuned from less than 1 OH/1000 C to 120 OH/1000 C (for pure poly(5hydroxy-cis-cyclooctene)) in the polymer backbone. The E


Article

Macromolecules

extrusion.132 Commercially available maleic anhydride-grafted polyethylene (Yparex OH07) was treated with 2-aminoethanol in an extruder to obtain the corresponding N-(2-hydroxyethyl)succinimide-grafted polyethylene. The successful transformation of succinic anhydride into N-(2-hydroxyethyl)succinimide functionality was proven by FT-IR spectroscopy. In the FT-IR spectra, depicted in Figure S10, two new bands originating from N-(2-hydroxyethyl)succinimide CO stretching vibrations can be distinguished at 1705 and 1774 cm−1 while the signals of succinic anhydride, present in Yparex OH07 before the reaction with ethanolamine, visible at 1713, 1791, and 1886 cm−1 have vanished. For chain-end-functionalized PE’s, in-reactor functionalization by means of CCTP followed by oxidation and hydrolysis seems to be the best scalable method, but the oxidation step is not quantitative and might lead to safety issues when oxygen is used as oxidizer. For producing randomly hydroxyl-functionalized PE, reactive extrusion is by far the simplest and wellscalable process as it can be performed in an extruder starting from commercially available precursors. The drawback of this process is, however, that the products are ill-defined with typically a broad molecular weight and broad functionality distribution. Polyethylene−Polyester Block Copolymers. Polyethylene−polyester block copolymers were prepared by catalytic ring-opening polymerization (cROP) of lactones as well as by transesterification of presynthesized polyesters, using chain-end hydroxyl-functionalized polyethylene (HDPE-OH) as macroinitiator, and the efficiencies of both approaches have been compared. A wide variety of catalysts are known to ring-open lactones, both strained and unstrained.142−146 ε-Caprolactone (CL) and ω-pentadecalactone (PDL) were used as the lactones for the cROP toward polyethylene-block-polyester copolymers, using two different aluminum salen complexes 1 and 2 as catalysts (Scheme 2).147,148 To optimize the copolymerization process, various reaction conditions for the cROP were screened (Table 3).

molecular weights of the polymers were regulated by adding 1octene as chain transfer agent (CTA), and the polymerizations were terminated by addition of ethyl vinyl ether. Table 2 Table 2. Ring-Opening Metathesis Copolymerization of Cyclooctene and 5-Hydroxycyclooctene entry M0/cat.b M0/CTAc 1 2 3 4 5

4000 8000 4000 2000 4000

100 100 100

5HCOd [mol %]

5HCOe [mol %]

Mnf [g mol−1]

ĐMf

3 3 3 3 5

2.8 2.5 2.9 2.9 4.4

42640 38130 9500 7100 8840

1.9 2.0 2.4 2.1 2.0

a

Conditions: initial amount of cyclooctene 1 g, reactions performed in toluene (15 mL) at room temperature, reaction time 24 h. bMonomerto-catalyst molar ratio. cMonomer-to-CTA (1-octene) molar ratio. d Refers to the percentage of 5-hydroxycyclooctene (5HCO) in the polymerization mixture. eRefers to the percentage of 5-hydroxycyclooctene (5HCO) calculated from NMR spectra. fMolecular weight and polydispersity determined by HT-SEC in TCB at 160 °C. Melting point of entry 3 (Tm = 129.4 °C).

summarizes the polymerization conditions and properties of the prepared unsaturated polymers. The results presented in Table 2 clearly show that addition of 1-octene as CTA significantly lowers the Mn of the polymers (Table 2, entries 3−5) in comparison to the polymerizations performed without CTA (Table 2, entries 1 and 2). Furthermore, to examine the influence of the monomer:catalyst ratio on the polymers’ molecular weight, experiments with [M]:[cat.] ratios equal to 4000:1 and 8000:1 (entries 1 and 2 in Table 2) were performed. Although a doubling of the monomer:catalyst ratio was assumed to increase the polymers molecular weight, it was found not to affect Mn values significantly. It is plausible that a combination of high monomer conversion and high viscosity leads to diffusion limitation and competitive intramolecular cross-metathesis affording cyclic products, preventing a significant increase in molecular weight.119 To obtain randomly hydroxyl-functionalized HDPE, the products prepared by ROMP were hydrogenated. Recorded NMR spectra (see Figure S5) show the quantitative hydrogenation of the unsaturated bonds of the polymer samples whereas the hydroxyl functionalities are unaffected by the hydrogenation process. Successful hydrogenation was also confirmed by DSC analysis (Figure S6). DSC experiments revealed a melting transition at around 50 °C for the polymer before hydrogenation. The presence of melting−crystallization transitions indicates that the second-generation Grubbs catalyst catalyzes not only olefin metathesis but also the isomerization of the unsaturated bonds in the polymer into the more stable transisomers forming a semicrystalline product. The enthalpy of the transition is rather small in comparison to that of the corresponding hydrogenated product, indicating that the polymer entails significant imperfections. Hydrogenation of the unsaturated polymers leads to highly crystalline polyethylene with a typical melting transition around 126 °C. The fact that the melting point is about 10 °C lower than for unfunctionalized HDPE is clearly the result of the presence of OH groups, which are excluded from the crystal and are thus responsible for a lower melting transition. Finally, for comparison reasons, randomly hydroxyl-functionalized polyethylene (PE-OH) was also prepared by reactive

Scheme 2. Catalytic Ring-Opening Polymerization of CL and PDL toward Block and Graft Copolymersa

a

The reactions were mediated by aluminum−salen complexes 1 and 2 and hydroxyl-functionalized polyethylene as an initiator.

Catalyst 2 revealed a higher activity than 1 for the ROP of both CL and PDL, which reflected a higher molecular weight of the synthesized block copolymers. In Table 3 cROP of CL and PDL mediated by 2 and hydroxyl end-capped HDPE with the molar ratio [monomer]/[catalyst]/[HDPE-OH] equal to 1000/1/1 is presented. The relatively high polydispersities for a cROP product are the result of the polydispersity of the F


Article

Macromolecules Table 3. Catalytic Ring-Opening Polymerization of CL and PDL Affording HDPE−Polyester Block Copolymersa entry CL/PDL/cat./in. 1 2 3 4 5 6 7

1000/0/1/1 1000/0/1/1 1000/0/1/1 1000/0/1/1d 1000/0/1/1d 0/1000/1/1 0/1000/1/1

time [h]

Mnb [g mol−1]

ĐM b

monomer convc [%]

0.5 1 5 0.5 1 5 24

9940 18380 30110 46700 51000 47490 64580

1.9 1.7 1.6 1.7 1.6 1.6 2.0

95 97 99 95 95 42 91

Conditions of cROP: polymerizations performed at 100 °C catalyzed 2 using HDPE-OH with Mn = 2230 and ĐM = 2.1. bMolecular weight and polydispersity determined by HT-SEC in TCB at 160 °C.150 c Conversion of the lactones was estimated based on 1HNMR analysis. d Before the monomer was added the catalyst was activated with the HDPE-OH initiator in toluene for 12 h at 100 °C, Tm of PP-block-PCL copolymer (entry 1) Tm1 = 53.0 °C, Tm2 = 128.2 °C, Tm of PP-blockPPDL copolymer (entry 6), Tm1 = 127.6, Tm2 = 91.3 °C. a

Figure 1. 1H NMR spectra of HDPE-block-PCL copolymer (Table 3, entry 5).

respectively, confirmed a successful polymerization of CL and PDL (Figure 1 and Table 3). Recorded spectra revealed a high CL conversion (typically above 90%) during cROP. For PDL the monomer conversion was lower under the same reaction conditions. This can be assigned to the lower ester reactivity and lower ester concentration in PDL compared to CL. Extending the polymerization time to 24 h afforded a satisfying conversion. Formation of HDPE-block-PCL and HDPE-block-PPDL copolymers was also confirmed by MALDI-ToF-MS analysis (Figure S7). As MALDI-ToF-MS is restricted to the relatively low molecular weight fraction of the polymer samples, the cyclic PCL and PPDL are the most abundant products in the recorded m/z vicinities. The difference in m/z between isotope distributions of 114 Da corresponds to the K+ cationized PCL while the distributions of 240 Da distance match with K+ cationized PPDL cyclic macromolecules. Although many isotope patterns overlap, a detailed analysis of the spectra reveals also the presence of the expected linear HDPE-blockpolyesters. For example, for HDPE-block-PCL, in particular the patterns at e.g. 1634 m/z, can be assigned to overlapping isotope patterns of cyclic PCL and linear HDPE-block-PCL block copolymer (left side of Figure S7). Similar results were observed for HDPE-block-PPDL copolymers. As presented in Figure S7 (spectrum depicted on the right side of Figure S7), high intensity signals can be assigned to both cyclic PPDL and HDPE-block-PPDL copolymers. Importantly, additional proof of the formation of linear block copolymers is provided by the low-intensity signals B that can only be assigned to HDPEblock-PPDL species. Polyethylene−Polyester Graft Copolymers. Since cROP of lactones in the presence of HDPE-OH was successfully used for the synthesis of block copolymers, the same graf ting from approach was applied for the preparation of graft copolymers using randomly functionalized PEs as macroinitiators. Similarly, as was observed for the synthesis of HDPE-block-PCL and HDPE-block-PPDL copolymers, catalyst 2 showed a higher activity than 1 for the formation of polyethylene−polyester graft copolymers, and selected data are presented in Table 4. Two types of randomly hydroxyl-functionalized polyethylenes were used as macroinitiators: (i) a randomly hydroxylfunctionalized HDPE (HDPE-OHn: Mn = 9.5 kg mol−1, ĐM = 2.4), obtained by ring-opening metathesis copolymerization of cyclooctene and 5-hydroxycyclooctene, followed by hydrogenation and (ii) a hydroxyl-functionalized LLDPE (LLDPEOHn: Mn = 9.2 kg mol−1, ĐM = 2.1), containing randomly distributed hydroxyl-functionalized branches, which was pro-

macroinitiator (ĐM = 2.1) and possibly concurrent transesterification reactions on top of that. The formation of cyclic polyester structures of PCL and PPDL (see MALDI-ToF-MS analysis, Figure S7) indicates that transesterification indeed takes place. Comparing entries 4−6 in Table 3 reveals an interesting phenomenon. At first sight, the increase in molecular weight with reaction time seems to be easily explainable based on a gradual polymer growth, but when taking into account that after 0.5 h most of the monomer has already been consumed illustrates that a more complex situation is taking place. A likely scenario is that initially a mixture of HDPE-block-PCL and PCL homopolymer is formed (low molecular weight fraction clearly visible by GPC). The latter can be either linear, formed e.g. by water initiation, or cyclic, formed by intramolecular transesterification. What is formed after 0.5 h is most possibly not a thermodynamically stable product mixture.149 Extending the reaction time allows the system to gradually reach a thermodynamically stable product consisting of mainly HDPE-block-PCL copolymers with increased molecular weight from 10 to 30 kg mol−1.150 In order to confirm this hypothesis, catalyst 2 was first contacted with the HDPE-OH macroinitiator to ensure that the aluminum metal center is bonded to the macroinitiator, before the cROP of CL was performed (Table 3, entries 1−5). Indeed, both polymerizations provided high molecular weight block copolymers already after 0.5 h, after which the molecular weight did not change significantly anymore. It is assumed that due to the low concentration of the hydroxyl groups, the reaction of the aluminum alkyl precursor with the hydroxyl-terminated polyethylene is a relatively slow process. Without preactivation, traces of water present in the system might compete as an initiator producing lower molecular weight polyester homopolymers. Synthesized HDPE-block-PPDL copolymers revealed molecular weights ranging from 48 to 65 kg mol−1 associated with a lower conversion of PDL most likely due to mass transfer limitation in the highly viscous system. The formation of the HDPE−polyester block copolymers as well as conversion of CL and PDL was confirmed by liquid state 1H NMR spectroscopy (Figure 1). The disappearance of signals at 3.67 ppm (PE-OH −CH2OH), 4.12 ppm (CL −CH2OC(O)− and PDL −CH2OC(O)−) in combination with the appearance of new sets of resonances at 4.09 ppm (PCL −CH2OC(O)−) and PPDL −CH2OC(O)−), G


Article

Macromolecules

increase with increasing lactone to macroinitiator ratios (e.g., entries 1−3 or 4−6). Extraction experiments revealed that the amount of homopolyester, formed by water initiation or by transesterification (cyclic polyester), was limited in all cases, and the differences cannot explain the discrepancy between the measured molecular weights and the monomer-to-initiator ratio. Most likely, the obtained molecular weight values from high-temperature SEC in trichlorobenzene are incorrect as a result of the incompatibility and different solubility behavior of the apolar PE and polar polyester blocks of the graft copolymers.150 Hence, in-depth solution NMR spectroscopy was used to verify the formation of the graft copolymers. The formation of the HDPE-graft-PCL copolymers by cROP of CL and randomly functionalized HDPE-OHn was followed by 1H NMR and 2D NMR spectroscopy (Figure 2 and Figure S8). Similarly to the above-mentioned block copolymer formation, the rapid disappearance of the resonances around 3.67 ppm (HDPE-OHn ⟩CH(OH)) and 4.12 ppm (CL −CH2OC(O)−) and appearance of a new set of resonances at 4.09 ppm (PCL −CH2OC(O)−) confirmed a nearquantitative monomer conversion and HDPE-graf t-PCL copolymer formation under the applied reaction conditions. Given the structure of the HDPE-derived copolymers and the possible sequence of the different monomer residues, 2D NMR spectra viz. heteronuclear single quantum correlation spectrum (HSQC) and heteronuclear multiple-bond correlation spectrum (HMBC) have been recorded to identify the signals corresponding to the PCL units as well as ester linkage between HDPE and the PCL block. The examination of the signals at 3.66 ppm in the HSQC and HMBC spectra clearly proved the formation of PCL grafts. Since the position of the PCL end-group signals (−CH2OH) is the same in homo- and

Table 4. Catalytic Ring-Opening Polymerization of CL and PDL Affording HDPE-graf t-PCL, HDPE-graf t-PPDL, LLDPE-graf t-PCL, and LLDPE-graf t-PPDL Copolymers entry

CL/PDL/cat./in.

time [h]

Mnc [g mol−1]

ĐM c

CL/PDL convd [%]

1a 2a 3a 4a 5a 6a 7b 8b 9b 10b 11b 12b

1000/0/1/1 500/0/1/1 250/0/1/1 0/1000/1/1 0/500/1/1 0/250/1/1 1000/0/1/1 500/0/1/1 250/0/1/1 0/1000/1/1 0/500/1/1 0/250/1/1

2 2 2 5 5 5 2 2 2 5 5 5

24800 85900 20700 31400 59600 49400 17100 15400 12100 25000 18600 16300

2.1 2.3 2.8 2.5 3.5 2.5 2.5 2.7 2.5 4.8 4.2 2.6

97 94 90 88 94 92 94 95 99 83 86 85

Conditions of cROP: 100 °C, polymerizations mediated by 2 and randomly functionalized HDPE-OHn with Mn = 9.5 kg mol−1 and ĐM = 2.4. bPolymerizations mediated by 2 and randomly functionalized LLDPE-OHn with Mn = 9.2 kg mol−1 and ĐM = 2.1. cMolecular weight and polydispersity determined by HT-SEC in TCB at 160 °C. d Conversion of the lactones was estimated based on 1H NMR analysis. a

duced by copolymerization of ethylene and 10-undecene-1-ol. The performed cROP afforded graft copolymers with numberaverage molecular weights in the range from 13 to 86 kg mol−1. Again, the relatively broad polydispersity of the products originate from the broad polydispersity of the macroinitiator and the occurrence of transesterification as was proven by the formation of cyclic structures of PCL or PPDL. Surprisingly, the molecular weights of the graft copolymers do not seem to

Figure 2. The 500 MHz heteronuclear single quantum correlation spectrum (HSQC, left side) of HDPE-graft-PCL copolymer (Table 4, entry 2) and 500 MHz heteronuclear multiple-bond correlation spectrum (HMBC) of HDPE-graft-PCL copolymer (entry 2 in Table 4). H


Article

Macromolecules

Figure 3. 13C{1H} INEPT MAS NMR spectra (left) and 13C{1H} CP/MAS NMR spectra (right) of HDPE-block-PCL copolymer (Table 3, entry 2).

Figure 4. 13C{1H} INEPT MAS NMR spectra (left) and 13C{1H} CP/MAS NMR spectra (right) of HDPE-graft-PCL copolymer (Table 4, entry 2).

respectively. The distinctive melting transitions clearly indicate phase separation between the hydrophilic and hydrophobic domains. The enthalpy of the transition is comparable for both polymers. Besides, a shift of melting transition for the HDPE block in the copolymer can be observed, which is a clear indication that we are dealing with a graft copolymer rather than a polymer blend. The melting point depression for the HDPE block indicates that long PCL segments limit the crystallization capability of the polyolefin domains. Likewise, cROP of CL and PDL in the presence of LLDPEOHn, containing hydroxyl-functionalized short chain branches, resulted in comparable polyethylene-graft-polyester copolymers (Table 4). Based on the 1H NMR and GPC analysis of the synthesized LLDPE-graf t-PCL and LLDPE-graf t-PPDL copolymers and their comparison with HDPE-based products, it can be concluded that the latter ones revealed higher molecular weights and lower polydispersity under the same reaction conditions. As an alternative to the graf ting f rom approach by means of cROP, the block copolymers were also prepared using a graf ting onto approach. For this methodology, presynthesized PCL (Mn = 25.6 kg mol−1 and ĐM = 1.3) and PPDL (Mn = 35.6 kg mol−1 and ĐM = 1.9) were transesterified in the presence of PE-OH

block copolymers, a detailed analysis of the resonances at 4.89 ppm was crucial, which was assumed to correspond to the linking point of the graft to the HDPE chain. In the HSQC spectrum indeed a cross-signal is visible at 4.89/74.0 ppm, corresponding to the ⟩CH−O−C(O)CH2− correlation, while a cross-peak at 4.89/172.2 ppm in the HMBC spectrum reveals a correlation between the polyethylene proton next to the ester group and the carbonyl group of the PCL, ⟩CH−O− C(O)CH2−. The spectra indicate that approximately 54 mol % of CL is incorporated and involved in the formation of graft copolymer. The rest is most probably linear and cyclic homopolymer, an unavoidable side product of cROP where transesterification is taking place as side reaction. The successful synthesis of HDPE-graf t-PCL and HDPEgraf t-PPDL copolymers was also confirmed by DSC analysis. An example of a copolymer’s thermal analysis is depicted in Figure S9. The blue curve exhibits a melting transition of the initiator viz. HDPE with randomly distributed hydroxyl groups along the polymer backbone, which is well visible at around 130 °C. The black curve (Figure S9) represents the DSC’s second heating curve of HDPE-graf t-PCL copolymer. The presence of two peaks at around 60 and 120 °C is characteristic for melting transitions of polycaprolactone and polyethylene blocks, I


Article

Macromolecules

Figure 5. Scanning electron micrographs of (a) freeze-fractured uncompatibilized LDPE/PC 80/20 w/w blend, (b) LDPE/PC 80/20 w/w blend compatibilized by 5 wt % of HDPE-graft-PCL where the compatibilizer was prepared by the grafting onto approach using PCL and Yparex OH07, and (c) LDPE/PC blend 80/20 w/w compatibilized by 5 wt % of HDPE-graf t-PCL copolymer (entry 1 in Table 4). The light spots visible in the micrographs are not the separate phases but inclined planes formed after specimen rupture being not completely covered by gold while preparing the samples.

(Mn = 12.6 kg mol−1 and ĐM = 3.2) as macroinitiator. Besides the disappearance of the −CH2OH resonance, NMR was not very informative. Therefore, the reaction was followed by FTIR. The FT-IR spectrum of PE-OH shows two CO stretching at 1705 and 1774 cm−1, which vanish while new vibrations appear at 1726 and 1738 cm−1. The big advantage is that transesterification is a very simple approach toward producing block copolymers. The obvious drawback of transesterification route is the presence of residual homopolyester and that the polyester block length in the block copolymer depending on the polyester’s molecular weight and polyester/PE-OH ratio. Both the copolymer prepared by transesterification and a tailor-made products synthesized by cROP of lactones were applied as compatibilizers of PE/PC blends (see below). Solid-State NMR Analysis. To elucidate molecular mobility and local conformations in the synthesized block and graft copolymers, solid-state 13C{1H} cross-polarization magic-angle spinning (CP/MAS) NMR was employed. This technique offers insight into conformational distributions of rigid polymer segments via carbon (13C) chemical shifts as reflected in their isotropic chemical shift values and the line shape. As a complementary technique to better understand the melting and the increasing molecular mobility of the different polymer segments upon heating, the refocused 13C{1H} insensitive nuclei enhanced by polarization transfer (INEPT) MAS sequence was used. Figures 3 and 4 summarize the results acquired both for polyethylene−polyester block and graft copolymers. The left figures represent 13C{1H} INEPT MAS NMR spectra while the right ones show CP/MAS NMR results. For both block and graft copolymers the carbonyl group resonances in the CP/MAS spectrum (signals 5 and 4 at ∼175 ppm in Figures 3 and 4) exhibit a complex line shape with a relatively sharp feature manifesting significant chain dynamics with rapid conformational exchange and an underlying broad component observed at slightly lower ppm values that clearly confirms a semicrystalline character of the PCL block. At elevated temperature the carbonyl resonances shift toward slightly higher ppm values and above 50 °C they vanish, as crystalline PCL fragments are melting. The disappearance of the carboxyl signal coincides with a substantial decrease in intensity of all PCL signals in the CP/MAS spectra, which can be easily explained by an enhanced mobility of PCL above its

melting point (Tm(PCL) ∼ 56 °C) reducing the heteronuclear dipolar couplings required to record CP/MAS spectra. These results are in an agreement with 13C{1H} INEPT MAS NMR experiments where high-intensity PCL resonances dominate above 70 °C (e.g., signals 6−10 in Figure 3 and signals 5−9 in Figure 4 for a block and graft copolymers, respectively) the acquired spectra. The PE fragments become mobile only at higher temperatures. In the 13C{1H} INEPT MAS NMR spectra resonances of amorphous PE start to be visible around 110 °C at 30 ppm, whereas in the CP/MAS NMR spectra signals of crystalline and amorphous PE are seen as very broad weak peaks at 33 and 31 ppm, respectively. The crystalline signal vanishes around 110 °C, when the amorphous PE signal starts to grow in the INEPT MAS NMR experiment. The observed melting temperature, which was found to be well below the regular melting point of PE (Tm(PE) ∼ 120−130 °C), indicates that the PE segments in the synthesized copolymers can form only small crystallites (Gibbs−Thomson equation).151 Based on these findings, also the differences in intensities of the signals in liquid state NMR spectra can be explained. Most likely the dissimilarity in the intensities of the −CH2OH and ⟩CH−O−C(O)− signals, presented in Figure 2, are caused by different mobility and different T2 relaxation of PE and PCL polymer fragments. Both cROP and transesterification as methods to produce block/graft copolymers have their advantages and disadvantages. Especially on the lab scale, cROP is a very well-controlled polymerization reaction, reaching high monomer conversion and providing polyesters with narrow polydispersities. When a PE-OHn is used as the macroinitiator, the situation changes significantly. For reaction to take place, generally the PE-OHn has to be dissolved, which is undesirable on a commercial production scale, and although monomer conversion can be quite high, even the few percent of unreacted lactone (volatile organic compound, VOC) would be unacceptable in most commercial applications. Hence, the product will have to be precipitated and dried. Furthermore, the molecular weight distribution of the block/graft copolymer is at least as broad as that of the macroinitiator, which is typically 2 or higher. Transesterification is a very practical and easily scalable process for producing block/graft copolymers as it can be performed in an extruder. The obvious drawback of this approach is that not all of the polyester is used to produce the block/graft J


Article

Macromolecules

Figure 6. Scanning electron micrographs of (a) freeze-fractured uncompatibilized HDPE/PC 80/20 w/w blend, (b) HDPE/PC 80/20 w/w blend compatibilized by 5 wt % of HDPE-graft-PCL prepared by grafting onto approach from PCL and Yparex OH07, and (c) LDPE/PC blend 80/20 w/ w compatibilized by 5 wt % of HDPE-graf t-PCL copolymer (entry 1 in Table 4). The light spots visible in the micrographs are not the separate phases but inclined planes formed after specimen rupture being not completely covered by gold while preparing the samples.

Figure 7. Left: stress−strain curves of (a) LDPE, (b) uncompatibilized LDPE/PC 80/20 w/w blend, (c) LDPE/PC 80/20 w/w blend compatibilized by 5 wt % of HDPE-graf t-PCL prepared by graf ting onto approach from PCL and Yparex OH07 in a mini-extruder (I), and (d) LDPE/PC blend 80/20 w/w compatibilized by 5 wt % of HDPE-graf t-PCL copolymer (II, entry 1 in Table 4). Right: (a) HDPE, (b) uncompatibilized HDPE/PC 80/20 w/w blend, (c) HDPE/PC 80/20 w/w blend compatibilized by 5 wt % of HDPE-graf t-PCL prepared by grafting onto approach from PCL and Yparex OH07 in a mini-extruder (I), and (d) HDPE/PC blend 80/20 w/w compatibilized by 5 wt % of HDPE-graftPCL copolymer (II, entry 1 in Table 4).

copolymer. A certain fraction of polyester invariably remains, which might have undesired effects depending on the targeted application. For example, when used as compatibilizer in blends the remaining homopolyester can have a plasticizing effect on the dispersed phase of a blend (vide inf ra). To reduce the polyester fraction while still producing block/graft copolymers with reasonably long polyester blocks, a very high molecular weight polyester to start with will be required, which is challenging to produce. Block and Graft Copolymers as Compatibilizers for Polymer Blends. The performance of the copolymers as compatibilizers for blends of polyethylene and bisphenol A polycarbonate (PC) was verified by comparing the morphology of LDPE/PC and HDPE/PC blends (Figure 5 and 6) compatibilized with HDPE-graf t-PCL graft copolymers synthesized via cROP of CL and by transesterification of PCL with hydroxyl-functionalized HDPE (Yparex OH07) in a miniextruder. Additionally, both LLDPE-graf t-PCL copolymers were tested as compatibilizers of the investigated blends. The representative SEM image of the uncompatibilized blend clearly shows the lack of adhesion between the polar PC and the apolar LDPE or HDPE phase. Upon adding 5 wt % of the above-mentioned compatibilizers, the adhesion between PE

and PC significantly improved. This effect is qualitatively visible for both LLDPE/PC and HDPE/PC compositions where the dispersed phased is broken rather than pulled out of the matrix and the droplet size of the dispersed PC phase clearly reduces. Not surprisingly, HDPE-block-PCL copolymers, prepared by cROP initiated by PE-OHn and consisting of a rather short PE block (Mn just above 2 kg mol−1), did not enhance the miscibility between PE and PC phases. For good compatibilization, it was found crucial to have PE and PCL block lengths of Mn > 9 kg mol−1. Besides the synthesized by cROP LLDPEgraf t-PCL copolymers proved to be unsuitable as compatibilizer for LDPE/PC and HDPE/PC as no significant improvement of the blends morphology was observed. Most likely, the used LLDPE-graf t-PCL contains too many (short) graftsas the LLDPE-OHn contained 3 mol % of hydroxyl-functionalized comonomerto effectively interact with both the LDPE or HDPE matrix and the PC dispersed phase. Figure 7 shows tensile test results of the LDPE/PC and HDPE/PC blends compared with the tensile test results of neat LDPE and HDPE. The maximum stress values, elongation at break, and impact data for different samples compositions are presented in Table S1. Note that for comparison reasons the tensile tests were performed for samples prepared by injection K


Article

Macromolecules

decreased as the weight fraction of PEs in the polymer blends decreased.

molding. While LDPE and HDPE show performances typical for ductile materials with a plastic deformation, PC undergoes elastic deformation followed by a brittle fracture already at low elongation. Hence, it was expected that the LDPE/PC and HDPE/PC blends could be toughened even for the polyolefinrich compositions. SEM analysis indicates that upon stretching of the materials PC particles debond from the oriented HDPE matrix. The presence of HDPE-graf t-PCL (Table 4 entry 1), as the compatibilizer of HDPE/PC blend, improves significantly the adhesion between the phases (Figures 6b,c and 7), which is clearly reflected by an enhanced elongation at break of the HDPE-rich samples during tensile tests being above 310%. The impact strength analyses were performed at room temperature. Table S1 summarizes the impact data of the compatibilized PE/ PC blends and their uncompatibilized references. For the LDPE/PC blends compatibilized by HDPE-graf t-PCL copolymers, the maximum stress and elongation at break change from 25 MPa and 61% for pure LDPE to 28 MPa and 51% for LDPE/PC (80/20) blend compatibilized by HDPE-graf t-PCL, clearly showing that the adhesion between the matrix and dispersed phase is improved. This can also be explained by lower stress concentration on small PC particles in the blends during failure. The effect of incorporation of PC, as a dispersed phase revealing an enhanced compatibility to PE, is slightly visible for LDPE-rich samples. The izod impact strength of the compatible LDPE/PC blend, containing only 20 wt % of PC, increased around 25% when compared to pure LDPE (see Table S1). The presence of PC dispersed in the HDPE matrix did not affect the impact strength of the materials at room temperature when compared to the neat HDPE. The tensile tests of HDPE and HDPE/PC blends reveal a clear presence of yield point and necking. An incorporation of PC, as a dispersed phase, enhances maximum stress of the samples (38 MPa for the uncompatibilized HDPE/PC blend versus 30 MPa measured for HDPE); nonetheless, their elongation at break is still unsatisfactory (around 30%). Such a behavior can be easily explained in view of SEM micrographs of the uncompatibilized blend (Figure 6a). Furthermore, to characterize the surface properties of the polymer blends, the contact angles between water droplets and the surfaces of the polymer blends were measured. As presented in Table S1, the incorporation of PC, as a dispersed phase in LDPE or HDPE matrix, changed the contact angle of the materials significantly. Taking the water contact angle of HDPE (Θ = 97.2 ± 1.7°), LDPE (Θ = 92.6 ± 0.5°), and PC (Θ = 81.4 ± 1.1°) into account, the PE/PC 80/20 w/w blends, where PC forms only a minor dispersed fraction of the blend, already show a significant change in hydrophilicity. The most pronounced changes were observed for the HDPE-rich (HDPE/PC 80/20 w/w) blends compatibilized by HDPEgraf t-PC where the water contact angle of the materials decreased from 97.2° for pure HDPE to 83.4°, very close to that of pure PC. As DSC analysis is widely used for studying melting/ crystallization behavior, we examined the LDPE and HDPE reference samples as well as their uncompatibilized and compatibilized blends with PC. The experiments proved that both the melting and crystallization points of the polyolefins (LDPE 115 °C and HDPE 132 °C) were not significantly affected by the presence of the polycarbonate (Table S2 and Figure S11). However, the enthalpies of these transitions

■

CONCLUSION In summary, we have compared different routes to produce chain-end and randomly hydroxyl-functionalized polyethylenes as well as different approaches for producing the corresponding block and graft copolymers. Hydroboration followed by oxidation using H2O2/NaOH proved to be a highly effective but cumbersome method for producing chain-end-functionalized PE’s, which can only be performed efficiently at the lab scale. CCTP followed by oxidation with O2 afforded welldefined products, but the degree of functionality of just over 80% is lower than for the hydroboration route (95+%). Nevertheless, CCTP seems to be the most promising route to produce chain-end hydroxyl-functionalzied PE’s on a large scale. Which is the preferred route to produce randomly functionalized PE’s strongly depends on the functionalization level. For PE’s with a low concentration of hydroxyl groups, the one-step copolymerization of ethylene and hydroxyl-functionalized olefinspacified with aluminum alkylsis an effective route. The increasing catalyst poisoning with increasing comonomer concentration prevents high comonomer incorporation levels at decent catalyst activity. Hence, for polyolefins with moderate to high hydroxyl content, the consecutive ROMP−hydrogenation process is the preferred approach. Reactive extrusion (i.e., HDPE + maleic anhydride followed by 2-aminoethanol) is by far the most practical and easily scalable route to produce PE-OHn with a low to moderate functionality level. Polyethylene−polyester block and graft copolymers have been produced by both cROP of lactones or transesterification of a presynthesized polyesters with OH-functionalized HDPE as the macroinitiator. Both methods have their advantages and disadvantages. cROP is generally a well-controlled process leading to highly uniform copolymer structures. However, incomplete monomer conversion and concurrent transesterification led to undesired volatile organic components and low molecular weight cyclic homopolyester as side products, albeit in low quantities. Transesterification of presynthesized polyesters appeared to be a simple and convenient approach for producing block and graft copolymers but the transesterification process invariably results in a certain amount of low polyester as side product, which might be difficult to remove and might have a plastisizing effect of the dispersed PC phase. Clearly, the efficiency of this process increases with increasing molecular weight of the polyesters. The copolymers were subsequently applied as compatibilizers of PE/PC blends. For good compatibilization, it was found crucial to have PE and PCL block lengths of Mn > 9000 g mol−1. The SEM micrographs, recorded for the PE/PC blends compatibilized using HDPE-graf t-PCL copolymers, revealed a significantly improvement morphology in comparison to the corresponding uncompatibilized blends and the improved adhesion between the two phases find also expression in the mechanical and surface properties of the blends.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.6b02341. L


Article

Macromolecules

■

polyethylene copolymers via grafting-through atom transfer radical polymerization. J. Appl. Polym. Sci. 2007, 105, 3−13. (20) Sainath, A.; Isokawa, M.; Suzuki, M.; Ishii, S.; Matsuura, S.; Nagai, N.; Fujita, T. Synthesis and characterization of succinic anhydride- and disodium succinate-terminated low molecular weight polyethylenes. Macromolecules 2009, 42, 4356−4358. (21) Wiedemann, T.; Voit, G.; Tchernook, A.; Roesle, P.; GöttkerSchnetmann, I.; Mecking, S. Monofunctional hyperbranched ethylene oligomers. J. Am. Chem. Soc. 2014, 136, 2078−2085. (22) Yanjarappa, M.; Sivaram, S. Synthesis of poly(1-hexene)s endfunctionalized with phenols. Polym. Int. 2005, 54, 1310−1313. (23) Norsic, S.; Thomas, C.; D’Agosto, F.; Boisson, C. Divinyl-endfunctionalized polyethylenes: Ready access to a range of telechelic polyethylenes through thiol-ene reactions. Angew. Chem., Int. Ed. 2015, 54, 4631−4635. (24) Boffa, L. S.; Novak, B. M. Copolymerization of polar monomers with olefins using transition metal complexes. Chem. Rev. 2000, 100, 1479−1493. (25) Functionalization of Polyolefins; Chung, T. C., Ed.; Academic Press: London, 2002. (26) Franssen, N. M. G.; Reek, J.; N, H.; de Bruin, B. Synthesis of functional ‘polyolefins’: State of the art and remaining challenges. Chem. Soc. Rev. 2013, 42, 5809−5832. (27) Amin, S. B.; Marks, J. T. Versatile pathways for in situ polyolefin functionalization with heteroatoms: catalytic chain transfer. Angew. Chem., Int. Ed. 2008, 47, 2006−2025. (28) Schellekens, M. A. J.; Klumperman, B. Synthesis of polyolefin block and graft copolymers. J. Macromol. Sci., Polym. Rev. 2000, 40, 167−192. (29) Lopez, R. G.; D’Agosto, F.; Boisson, C. Synthesis of well-defined polymer architectures by successive catalytic olefin polymerization and living/controlled polymerization reactions. Prog. Polym. Sci. 2007, 32, 419−454. (30) Koo, K.; Marks, T. Silanolytic chain transfer in Ziegler-Natta catalysis. Organotitanium-mediated formation of new silapolyolefins and polyolefin architectures. J. Am. Chem. Soc. 1998, 120, 4019−4020. (31) Xu, G.; Chung, T. C. Borane chain transfer agent in metallocene-mediated olefin polymerization. Synthesis of boraneterminated polyethylene and diblock copolymers containing polyethylene and polar polymers. J. Am. Chem. Soc. 1999, 121, 6763−6764. (32) Imuta, J.; Kashiwa, N.; Toda, Y. Catalytic regioselective introduction of allyl alcohol into the nonpolar polyolefins: development of one-pot synthesis of hydroxyl-capped polyolefins mediated by a new metallocene IF catalyst. J. Am. Chem. Soc. 2002, 124, 1176− 1177. (33) Kawaoka, A. M.; Marks, T. J. Organolanthanide-catalyzed synthesis of phosphine-terminated ployethylenes. J. Am. Chem. Soc. 2004, 126, 12764−12765. (34) Amin, S. B.; Marks, T. J. Organolanthanide-catalyzed synthesis of amine-capped polyethylenes. J. Am. Chem. Soc. 2007, 129, 10102− 10103. (35) Makio, H.; Fujita, T. Synthesis of chain-end functionalized polyolefins with a bis(phenoxy imine) titanium catalyst. Macromol. Rapid Commun. 2007, 28, 698−703. (36) Lin, W.; Niu, H.; Chung, T. C.; Dong, J. Y. Borane chain transfer reaction in olefin polymerization using trialkylborane as chain transfer agent. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 3534− 3541. (37) Chung, T. C.; Dong, J. Y. A novel consecutive chain transfer reaction to p-methylstyrene land hydrogen during metallocenemediated olefin polymerization. J. Am. Chem. Soc. 2001, 123, 4871− 4876. (38) Dong, J. Y.; Wang, Z. M.; Hong, H.; Chung, T. C. Synthesis of isotactic polypropylene containing a terminal Cl, OH, or NH2 group via metallocene-mediated polymerization/chain transfer reaction. Macromolecules 2002, 35, 9352−9359. (39) Lee, J.-Y.; Tsai, J.-C. End-functionalization of isotactic polypropylene via consecutive chain transfer reaction to norborna-

Liquid-state NMR, MALDI-ToF-MS, static mechanical properties, surface properties, and DSC analysis (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (L.J.-W.). *E-mail: [email protected] (R.D.). ORCID

Michael Ryan Hansen: 0000-0001-7114-8051 Rob Duchateau: 0000-0002-2641-4354 Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS The financial support from SABIC is gratefully acknowledged. REFERENCES

(1) Handbook of Polyolefins; Vasile, C., Ed.; Marcel Dekker: 2000. (2) Stereoselective Polymerization with Single-Site Catalysts; Baugh, L. S., Canich, J. A. M., Eds.; CRC Press: 2008. (3) Polyolefin Reaction Engineering; Soares, J. B. P., McKenna, T. F. L., Eds.; , Wiley-VCH: Weinheim, 2012. (4) Polyolefins: 50 years after Ziegler and Natta I: Polyethylene and Polypropylene; Kaminsky, W., Ed.; Springer-Verlag: 2013. (5) Erikson, M.; Cummins, A. Researchers combine education and outdoor adventure to help combat plastic pollution. Chem. Eng. News 2010, 88, 45. (6) Rios, L. M.; Jones, P. R.; Moore, C.; Narayan, U. V. Quantitation of persistent organic pollutants adsorbed on plastic debris from the Northern pacific Gyre’s “eastern garbage patch”. J. Environ. Monit. 2010, 12, 2226−2236. (7) Polymer Blends; Paul, D. R., Newman, S., Eds.; Academic Press: New York, 1978; Vol. 2. (8) Koning, C.; van Duin, M.; Pagnoulle, C.; Jerome, R. Strategies for compatibilization of polymer blends. Prog. Polym. Sci. 1998, 23, 707− 757. (9) Bates, F. S.; Frederickson, G. H. Block copolymers − Designer soft materials. Phys. Today 1999, 52, 32−38. (10) Ruzette, A.-V.; Leibler, L. Block copolymers in tomorrow’s plastics. Nat. Mater. 2005, 4, 19−31. (11) Shimodacho, T.; Sezume, C.; Nishihara, A.; Kobayashi, C.; Nishitsurugaoka, K.; Inamrori, C. Polypropylene-polyester graft copolymer and production method thereof. EP 0467958A4. (12) Gaylord, N. G.; Mehta, M. Role of homopolymerization in the peroxide-catalyzed reaction of maleic anhydride and polyethylene in the absence of solvent. J. Polym. Sci., Polym. Lett. Ed. 1982, 20, 481− 486. (13) Gaylord, N. G.; Mehta, M.; Mehta, R. Degradation and crosslinking of ethylene-propylene copolymer rubber on reaction with maleic anhydride and/or peroxides. J. Appl. Polym. Sci. 1987, 33, 2549−2558. (14) Wu, C. H.; Su, A. C. Functionalization of ethylene-propylene rubber via melt mixing. Polym. Eng. Sci. 1991, 31, 1629−1636. (15) Moad, G. The synthesis of polyolefin graft copolymers by reactive extrusion. Prog. Polym. Sci. 1999, 24, 81−142. (16) Russell, K. E. Free radical graft polymerization and copolymerization at higher temperatures. Prog. Polym. Sci. 2002, 27, 1007−1038. (17) Chung, T. C.; Lu, H. L.; Janvikul, W. A Novel synthesis of PP-bPMMA copolymers via metallocene catalysis and borane chemistry. Polymer 1997, 38, 1495−1502. (18) Lu, B.; Chung, T. C. New maleic anhydride modified PP copolymers with block structure: synthesis and application in PP/ polyamide reactive blends. Macromolecules 1999, 32, 2525−2533. (19) Kaneyoshi, H.; Matyjaszewski, K. Synthesis of a linear polyethylene macromonomer and preparation of polystyrene-graf tM


Article

Macromolecules diene and hydrogen. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 3739−3750. (40) Kempe, R. How to polymerize ethylene in a highly controlled fashion? Chem. - Eur. J. 2007, 13, 2764−2773. (41) Kurosawa, H.; Shiono, T.; Soga, K. Synthesis of α,ω-dialkenyl isotactic poly(propylene) using bis(4-methyl-3-pentenyl)zinc as a chain transfer reagent. Macromol. Chem. Phys. 1994, 195, 3303−3309. (42) Kojoh, S.; Kioka, M.; Kashiwa, N.; Itoh, M.; Mizuno, A. A study of chain-end structures of propylene prepared with MgCl2-supported titanium catalyst. Polymer 1995, 36, 5015−5018. (43) Pelletier, J.-F.; Mortreux, A.; Bujadoux, K.; Olonde, X.; Bujadoux, K. Synthesis of new dialkylmagnesium compounds by living transfer ethylene oligo- and polymerization with lanthanide catalysts. Angew. Chem., Int. Ed. Engl. 1996, 35, 1854−1856. (44) Valente, A.; Zinck, P.; Mortreux, A.; Bria, M.; Visseaux, M. Half lanthanocene/dialkylmagnesium-mediated coordinative chain transfer copolymerization of styrene and hexene. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 3778−3782. (45) Britovsek, G.; Bruce, M.; Gibson, V.; Kimberley, B.; Maddox, P.; Mastroianni, S.; McTavish, S.; Redshaw, C.; Solan, G.; Strömberg, S.; White, A.; Williams, D. Iron and cobalt ethylene polymerization catalysts bearing 2,6-bis(imino)pyridyl ligands: Synthesis, structures, and polymerization studies. J. Am. Chem. Soc. 1999, 121, 8728−8740. (46) Rogers, J. S.; Bazan, G. C. Oligomerization−transmetalation reactions of Cp*CrMe2(PMe3)/methylaluminoxane catalysts. Chem. Commun. 2000, 1209−1210. (47) Britovsek, G.; Cohen, S.; Gibson, V.; Maddox, P.; van Meurs, M. Iron-catalyzed polyethylene chain growth on zinc: Linear α-olefins with a Poisson distribution. Angew. Chem., Int. Ed. 2002, 41, 489−491. (48) Arriola, D. J.; Carnahan, E. M.; Hustad, P. D.; Kuhlman, R. L.; Wenzel, T. T. Catalytic production of olefin block copolymers via chain shuttling polymerization. Science 2006, 312, 714−719. (49) Wei, J.; Zhang, W.; Sita, L. R. Aufbaureaktion redux: Scalable production of precision hydrocarbons from AlR3 (R = Et or iBu) by dialkyl zinc mediated ternary living coordinative chain-transfer polymerization. Angew. Chem., Int. Ed. 2010, 49, 1768−1772. (50) Makio, H.; Ochiai, T.; Mohri, J.-I.; Takeda, K.; Shimazaki, T.; Usui, Y.; Matsuura, S.; Fujita, T. Synthesis of telechelic olefin polymers via catalyzed chain growth on multinuclear alkylene zinc compounds. J. Am. Chem. Soc. 2013, 135, 8177−8188. (51) Doi, Y.; Hizal, G.; Soga, G. Synthesis and characterization of terminally functionalized polypropylene. Makromol. Chem. 1987, 188, 1273−1279. (52) Shiono, T.; Yoshida, K.; Soga, K. Synthesis of ternally hydroxylated isotactic polypropylene using Zn(C2H5)2 and oxygen as chain transfer and quenching reagents. Makromol. Chem., Rapid Commun. 1990, 11, 169−175. (53) Shiono, T.; Kang, K. K.; Hagihara, H.; Ikeda, T. Novelty of vinylidene-terminated polypropylene prepared by a MgCl2-supported TiCl4 catalyst combined with AlEt3 as cocatalyst. Macromolecules 1997, 30, 5997−6000. (54) Kang, K. K.; Shiono, T.; Ikeda, T. Synthesis of aluminum terminated polypropylene by a MgCl2-supported TiCl4 catalyst combined with Al(i-Bu)3 as cocatalyst. Macromolecules 1997, 30, 1231−1233. (55) Han, C. J.; Lee, M. S.; Byun, D. J.; Kin, S. Y. Synthesis of hydroxyl-terminated polyethylene via controlled chain transfer reaction and poly(ethylene-b-caprolactone) block copolymer. Macromolecules 2002, 35, 8923−8925. (56) Pillai, S.; Kretschmer, W.; Trebbin, M.; Förster, S.; Kempe, R. Tailored nanostructuring of end-group-functionalized high-density polyethylene synthesized by an efficient catalytic version of Ziegler’s “Aufbaureaktion. Chem. - Eur. J. 2012, 18, 13974−13978. (57) Schwab, F. C. Graft copolymers of polyethylene and polycaprolactone. US 5321088A. (58) Hillmyer, M.; Nguyen, S.; Grubbs, R. Utility of ruthenium metathesis catalyst for the preparation of end-functionalized polybutadiene. Macromolecules 1997, 30, 718−721.

(59) Pitet, L.; Amendt, M.; Hillmyer, M. Nanoporous linear polyethylene from a block polymer precursor. J. Am. Chem. Soc. 2010, 132, 8230−8231. (60) Schwendeman, J.; Wagener, K. Synthesis of amorphous hydrophobic telechelic hydrocarbon diols via ADMET polymerization. Macromol. Chem. Phys. 2009, 210, 1818−1833. (61) Diallo, A. K.; Michel, X.; Fouquay, S.; Michaud, G.; Simon, F.; Brusson, J.-M.; Carpentier, J.-F.; Guillaume, S. M. α-Trialkoxysilyl functionalized polycyclooctenes synthesized by chain-transfer ringopening metathesis polymerization. Macromolecules 2015, 48, 7453− 7465. (62) Giannini, U.; Brückner, G.; Pellino, E.; Cassata, A. Stereospecific polymerization of monomers containing oxygen and nitrogen with Ziegler-Natta catalysts. J. Polym. Sci., Part B: Polym. Lett. 1967, 5, 527− 533. (63) Purgett, M.; Vogl, O. Functional polymers. XLVIII. Polymerization of ω-alkenoate derivatives. J. Macromol. Sci., Chem. 1987, 24, 1465−1481. (64) Kesti, M.; Coates, G.; Waymouth, R. Homogeneous ZieglerNatta Polymerization of functionalized monomers catalyzed by cationic group IV metallocenes. J. Am. Chem. Soc. 1992, 114, 9679− 9680. (65) Wilén, C.-E.; Luttikhedde, H.; Hjertberg, T.; Näsman, J. Polar activation in copolymerization of propylene and 6-tert-butyl-2-(1,1demethylhept-6-enyl)-4-methylphenol over a racemic [1,1′(dimethylsilyl)bis(η5-4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride/methylalumoxane catalyst system. Macromolecules 1996, 29, 8569−8575. (66) Aaltonen, P. Functionalization of polyethylenes via metallocene/methylaluminoxane catalyst. Eur. Polym. J. 1997, 33, 1187− 1190. (67) Goretzki, R.; Fink, G. Homogeneous and heterogeneous metallocene/MAO-catalyzed polymerization of trialkylsilyl-protected alcohols. Macromol. Rapid Commun. 1998, 19, 511−515. (68) Hakala, K.; Löfgren, B.; Helaja, T. Copolymerizatins of oxygenfunctionalized olefins with propylene using metallocene/methylaluminoxane catalyst. Eur. Polym. J. 1998, 34, 1093−1097. (69) Sahre, K.; Schulze, U.; Eichhorn, K.-J.; Voit, B. Kinetic studies of metallocene-catalyzed copolymerization of propene with 10-undecen1-ol using FTIR spectroscopy. Macromol. Chem. Phys. 2007, 208, 1265−1273. (70) Terao, H.; Ishii, S.; Mitani, M.; Tanaka, H.; Fujita, T. Ethylene/ polar monomer copolymerization behavior of bis(phenoxy−imine) Ti complexes: Formation of polar monomer copolymers. J. Am. Chem. Soc. 2008, 130, 17636−17637. (71) Liu, S.; Yao, Z.; Cao, K.; Li, B.; Zhu, S. Preparation of polar ethylene−norbornene copolymers by metallocene terpolymerization with triisobutylaluminium-protected but-3-en-1-ol. Macromol. Rapid Commun. 2009, 30, 548−553. (72) Yang, X.; Liu, C.; Wang, C.; Sun, X.; Guo, Y.-H.; Wang, X.; Wang, Z.; Xie, Z.; Tang, Y. [O−NSR]TiCl3-catalyzed copolymerization of ethylene with functionalized olefins. Angew. Chem., Int. Ed. 2009, 48, 8099−8102. (73) Zimmer, S.; Schöbel, A.; Halbach, T.; Stohrer, J.; Rieger, B. New curable propylene copolymers containing tert-butoxysilane side groups. Macromol. Rapid Commun. 2013, 34, 221−226. (74) Chen, Z.; Li, J.; Tao, W.; Sun, X.; Yang, X.; Tang, Y. Copolymerization of ethylene with functionalized olefins by [ONX] titanium complexes. Macromolecules 2013, 46, 2870−2875. (75) Schneider, M. J.; Schäfer, R.; Mülhaupt, R. Aminofunctional linear low density polyethylene via metallocene-catalysed ethylene copolymerization with N,N-bis(trimethylsilyl)-1-amino-10-undecene. Polymer 1997, 38, 2455−2459. (76) Stehling, U.; Stein, K.; Kesti, M.; Waymouth, R. metallocene/ borate−catalyzed polymerization of amino-functionalized α-olefins. Macromolecules 1998, 31, 2019−2027. (77) Stehling, U.; Stein, K.; Fischer, D.; Waymouth, R. Metallocene/ borate−catalyzed copolymerization of 5-N,N-diisopropylamino-1N


Article

Macromolecules pentene with 1-hexene or 4-methyl-1-pentene. Macromolecules 1999, 32, 14−20. (78) Hakala, K.; Helaja, T.; Löfgren, B. Synthesis of nitrogen− functionalized polyolefins with metallocene/methylaluminoxane catalysts. Polym. Bull. 2001, 46, 123−130. (79) Hagihara, H.; Tsuchihara, K.; Sugiyama, J.; Takeuchi, K.; Shiono, T. Copolymerization of propylene and polar allyl monomers with zirconocene/methylaluminoxane catalyst: Catalytic synthesis of amino-terminated isotactic polypropylene. Macromolecules 2004, 37, 5145−5148. (80) Kaya, A.; Jakisch, L.; Komber, H.; Pompe, G.; Pionteck, J.; Voit, B.; Schulze, U. Synthesis of oxazoline functionalized polypropylene using metallocene catalysts. Macromol. Rapid Commun. 2000, 21, 1267−1271. (81) Wang, X.; Wang, Y.; Shi, X.; Liu, J.; Chen, C.; Li, Y. Synthesis of well-defined functional isotactic polypropylenes via efficient copolymerization of propylene with ω-halo-α-alkenes by post-metallocene hafnium catalyst. Macromolecules 2014, 47, 552−559. (82) Thomas, T. S.; Hwang, W.; Sita, L. R. End-group functionalized poly(α-olefinates) as non-polar building blocks: self-assembly of sugarpolyolefin hybrid conjugates. Angew. Chem., Int. Ed. 2016, 55, 4683− 4687. (83) Younkin, T.; Connor, E.; Henderson, J.; Friedrich, S.; Grubbs, R.; Bansleben, D. Neutral, single-component nickel (II) polyolefin catalysts that tolerate heteroatoms. Science 2000, 287, 460−462. (84) Li, W.; Zhang, X.; Meetsma, A.; Hessen, B. Reaction of cationic palladium α-diimine complexes with nitrogen-containing olefins: branched polyethylene with carbazole functionalities. Organometallics 2008, 27, 2052−2057. (85) Daigle, J.; Piche, L.; Claverie, J. Preparation of functional polyethylenes by catalytic copolymerization. Macromolecules 2011, 44, 1760−1762. (86) Ravasio, A.; Boggioni, L.; Tritto, I. Copolymerization of ethylene with norbornene by neutral aryl phosphine sulfonate palladium catalyst. Macromolecules 2011, 44, 4180−4186. (87) Wucher, P.; Goldbach, V.; Mecking, S. Electronic influences in phosphinesulfonate palladium(II) polymerization catalysts. Organometallics 2013, 32, 4516−4522. (88) Contrella, N.; Sampson, J.; Jordan, R. Copolymerization of ethylene and methyl acrylate by cationic palladium catalysts that contain phosphino-diethyl phosphonate ancillary ligands. Organometallics 2014, 33, 3546−3555. (89) Jian, Z.; Mecking, S. Insertion homo- and copolymerization of diallyl ether. Angew. Chem., Int. Ed. 2015, 54, 15845−15849. (90) Jian, Z.; Mecking, S. Short-chain branched polar-functionalized linear polyethylenes via ”tandem catalysis. Macromolecules 2016, 49, 4057−4066. (91) Marathe, S.; Sivaram, S. Regioselective copolymerization of 5vinyl-2-norbornene with ethylene using zirconocene-methylaluminoxane catalysts: A facile route to functionalized polyolefins. Macromolecules 1994, 27, 1083−1086. (92) Nomura, K.; Liu, J.; Fujiki, M.; Takemoto, A. Facile, efficient functionalization of polyolefins via controlled incorporation of terminal olefins by repeated 1,7-octadiene insertions. J. Am. Chem. Soc. 2007, 129, 14170−14171. (93) Itagaki, K.; Nomura, K. Efficient synthesis of functionalized polyolefin by incorporation of 4-vinylcyclohexene in ethylene copolymerization using half-titanocene catalysts. Macromolecules 2009, 42, 5097−5103. (94) Du, G.; Long, Y.; Xue, J.; Zhang, S.; Dong, Y.; Li, X. 1,4Selective polymerization of 1,3-cyclohexadiene and copolymerization with styrene by cationic half-sandwich fluorenyl rare earth metal alkyl catalysts. Macromolecules 2015, 48, 1627−1635. (95) Wang, X.-Y.; Wang, Y.-X.; Li, Y.-S.; Pan, L. Convenient syntheses and versatile functionalization of isotactic polypropylene containing plentiful pendant styrene groups with high efficiency. Macromolecules 2015, 48, 1991−1998.

(96) Ramakrishnan, S.; Berluche, E.; Chung, T. C. Functional group containing copolymers prepared by the Ziegler−Natta process. Macromolecules 1990, 23, 378−382. (97) Chung, T. C.; Rhubright, D. Synthesis of functionalized polypropylene. Macromolecules 1991, 24, 970−972. (98) Chung, T. C.; Rhubright, D. Kinetic aspects of the copolymerization between α-olefins and borane monomer in ZieglerNatta catalyst. Macromolecules 1993, 26, 3019−3025. (99) Shiono, T.; Sugimoto, M.; Hasan, T.; Cai, Z. Facile synthesis of hydroxy-functionalized cycloolefin copolymer using ω-alkenylaluminum as comonomer. Macromol. Chem. Phys. 2013, 214, 2239−2244. (100) Handbook of Metathesis; Grubbs, R. H., Ed.; Wiley-VCH: Weinheim, 2003. (101) Valenti, D. J.; Wagener, K. B. Direct synthesis of well-defined polymers via acyclic diene metathesis (ADMET) polymerization. Macromolecules 1998, 31, 2764−2773. (102) Bielawski, C. W.; Grubbs, R. H. Highly efficient Ring-opening metathesis polymerization (ROMP) using a new ruthenium catalyst containing N-heterocyclic carbine ligands. Angew. Chem., Int. Ed. 2000, 39, 2903−2906. (103) Watson, M. D.; Wagener, K. B. Ethylene vinyl acetate copolymers via acyclic diene metathesis polymerization. Examining the effect of “long” precise ethylene run lengths. Macromolecules 2000, 33, 5411−5417. (104) Baughman, T. W.; van der Aa, E.; Lehman, S. E.; Wagener, K. B. Circumventing the reactivity ration dilemma: Synthesis of ethyleneco-methyl vinyl ether copolymer. Macromolecules 2005, 38, 2550− 2551. (105) Opper, K. L.; Markova, D.; Klapper, M.; Müllen, K.; Wagener, K. B. Precision phosphonic acid functionalized polyolefin architectures. Macromolecules 2010, 43, 3690−3698. (106) Leonard, J. K.; Wei, Y.; Wagener, K. B. Synthesis and thermal characterization of precision poly(ethylene-co-vinyl amine) copolymers. Macromolecules 2012, 45, 671−680. (107) Noonan, K. J. T.; Hugar, K. M.; Kostalik, H. A., IV; Lobkovsky, E. B.; Abruña, H. D.; Coates, G. W. Phosphonium-functionalized polyethylene: a new class of base-stable alkaline anion exchange membranes. J. Am. Chem. Soc. 2012, 134, 18161−18164. (108) Choucair, A.; Eisenberg, A. Control of amphiphilic block copolymer morphologies using solution conditions. Eur. Phys. J. E: Soft Matter Biol. Phys. 2003, 10, 37−44. (109) Checot, F.; Lecommandoux, S.; Gnanou, Y.; Klok, H. A. Water-soluble stimuli-responsive vesicles from peptide-based diblock copolymers. Angew. Chem., Int. Ed. 2002, 41, 1339−1343. (110) Gao, H.; Tan, Y.; Guan, Q.; Cai, T.; Liang, G.; Wu, Q. Synthesis, characterization and micellization of amphiphilic polyethylene-b-polyphosphoester block copolymers. RSC Adv. 2015, 5, 49376−49384. (111) Gao, H.; Hu, Z.; Guan, Q.; Liu, Y.; Zhu, F.; Wu, Q. Synthesis and thermoreversible gelation of coil-helical polyethylene-block-poly(γbenzyl-L-glutamate) diblock copolymer. Polymer 2013, 54, 4923− 4929. (112) Zhao, Y.; Gao, H.; Liang, G.; Zhu, F.; Wu, Q. Synthesis of welldefined amphiphilic branched polyethylene-graft-poly(N-isopropylacrylamide) copolymers by coordination copolymerization in tandem with RAFT polymerization and their self-assembled vesicles. Polym. Chem. 2014, 5, 962−970. (113) Wang, Y.; Hillmyer, M. A. Polyethylene-poly(L-lactide) diblock copolymers: Synthesis and compatibilization of poly(Llactide)/polyethylene blends. J. Polym. Sci., Part A: Polym. Chem. 2001, 39, 2755−2766. (114) Thurber, C. M.; Xu, Y.; Myers, J. C.; Lodge, T. P.; Macosko, C. W. Accelerating Reactive Compatibilization of PE/PLA Blends by an Interfacially Localized Catalyst. ACS Macro Lett. 2015, 4, 30−33. (115) Pepels, M. P. F.; Hofman, W. P.; Kleijnen, R.; Spoelstra, A. B.; Koning, C. E.; Goossens, H.; Duchateau, R. Block copolymers of PElike poly(pentadecalactone) and poly(L-lactide): Synthesis, properties, and compatibilization of polyethylene/poly(L-lactide) blends. Macromolecules 2015, 48, 6909−6921. O


Article

Macromolecules (116) Schneider, Y.; Azoulay, J. D.; Coffin, R. C.; Bazan, G. C. New polyethylene macroinitiators and their subsequent grafting by atom tansfer radical polymerization. J. Am. Chem. Soc. 2008, 130, 10464− 10465. (117) Inoue, Y.; Matsugi, T.; Kashiwa, N.; Matyjaszewski, K. Graft Copolymers from Linear Polyethylene via Atom Transfer Radical Polymerization. Macromolecules 2004, 37, 3651−3658. (118) Xu, Y.; Thurber, C. M.; Lodge, T. P.; Hillmyer, M. A. Synthesis and remarkable efficacy of model polyethylene-graf t-poly(methyl methacrylate) copolymers as compatibilizers in polyethylene/poly(methyl methacrylate) blends. Macromolecules 2012, 45, 9604−9610. (119) Schneider, Y.; Azoulay, J.; Coffin, R.; Bazan, G. New polyethylene macroinitiators and their subsequent grafting by atom transfer radical polymerization. J. Am. Chem. Soc. 2008, 130, 10464− 10465. (120) Stehling, U.; Malmström, E.; Waymouth, R.; Hawker, C. Synthesis of poly(olefin) graft copolymers by a combination of metallocene and “living” free radical polymerization techniques. Macromolecules 1998, 31, 4396−4398. (121) Liu, S.; Sen, A. Synthesis of novel linear polyethylene-based graft copolymers by atom transfer radical polymerization. Macromolecules 2001, 34, 1529−1532. (122) Chung, T. C. Synthesis of functional polyolefin copolymers with graft and block structures. Prog. Polym. Sci. 2002, 27, 39−85. (123) Kashiwa, N.; Matsugi, T.; Kojoh, S.; Kaneko, H.; Kawahara, N.; et al. Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 3657−3666. (124) Inoue, Y.; Matsugi, T.; Kashiwa, N.; Matyjaszewski, K. Graft copolymers from linear polyethylene via atom transfer radical polymerization. Macromolecules 2004, 37, 3651−3658. (125) Ring, J. O.; Thomann, R.; Mülhaupt, R.; Raquez, J.-M.; Degée, P.; Dubois, P. Controlled synthesis and characterization of poly[ethylene-block-(L,L-lactide)]s by combining catalytic ethylene oligomerization with “coordination-insertion” ring-opening polymerization. Macromol. Chem. Phys. 2007, 208, 896−902. (126) Shi, X.; Zhao, Y.; Gao, H.; Zhang, L.; Zhu, F.; Wu, Q. Synthesis of hyperbranched polyethylene amphiphiles by chain walking polymerization in tandem with RAFT polymerization and supramolecular self-assembly vesicles. Macromol. Rapid Commun. 2012, 33, 374−379. (127) Mu, J.; Yang, F.; Li, W.; Gong, D.; Liu, Z.; Jiang, F.; Chen, Z. Synthesis of amphiphilic linear-hyperbranched graft-copolymers via grafting based on linear polyethylene backbone. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2146−2154. (128) Wang, X.-Y.; Li, Y.-G.; Mu, H.-L.; Pan, L.; Li, Y.-S. Efficient synthesis of diverse well-defined functional polypropylenes with high molecular weights and high functional group contents via thio-halogen click chemistry. Polym. Chem. 2015, 6, 1150−1158. (129) Kaneko, H.; Saito, J.; Kawahara, N.; Matsuo, S.; Matsugi, T.; Kashiwa, N. Synthesis and characterization of polypropylene-based polymer hybrids linked poly(methyl methacrylate) and poly(2hydrocyethyl methacrylate). Polymer 2008, 49, 4576−4584. (130) Robin, J. J.; Boyer, C.; Boutevin, B.; Loubat, C. Synthesis and properties of polyolefin graft copolymers by a grafting “onto” reactive process. Polymer 2008, 49, 4519−4528. (131) Descour, C.; Macko, T.; Schreur-Piet, I.; Pepels, M.; Duchateau, R. RSC Adv. 2015, 5, 9658−9666. (132) Becquart, F.; Chalamet, Y.; Chen, J.; Zhao, Y.; Taha, M. Poly[ethylene-co-(vinyl alcohol)]-graft-poly(ε-caprolactone) synthesis by reactive extrusion, 1 − Structural and kinetic study. Macromol. Mater. Eng. 2009, 294, 643−650. (133) Dzugan, S. J.; Goedken, V. L. Factors affecting Al−C bond reactivity of tetradentate Shiff-base organoaluminum complexes. Inorg. Chem. 1986, 25, 2858−2864. (134) Licciulli, S.; Thapa, I.; Albahily, K.; Korobkov, I.; Gambarotta, S.; Duchateau, R.; Chevalier, R.; Schuhen, K. Towards selective ethylene tetramerization. Angew. Chem., Int. Ed. 2010, 49, 9225−9228.

(135) Augustine, C.; Kurur, N. D. Supercycled SWf-TPPM sequence for heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance. J. Magn. Reson. 2011, 209, 156−160. (136) Morris, G. A.; Freeman, R. Enhancement of nuclear magnetic resonance signals by polarization transfer. J. Am. Chem. Soc. 1979, 101, 760−762. (137) Burum, D. P.; Ernst, R. R. Net polarization transfer via a Jordered state for signal enhancement of low-sensitivity nuclei. J. Magn. Reson. 1980, 39, 163−168. (138) Doddrell, D. M.; Pegg, D. T.; Bendall, M. R. Distortionless enhancement of NMR signals by polarization transfer. J. Magn. Reson. 1982, 48, 323−327. (139) Saalwächter, K.; Lange, F.; Matyjaszewski, K.; Huang, C. F.; Graf, R. BaBa-xy16: Robust and broadband homonuclear DQ decoupling for applications in rigid and soft solids up to the highest MAS frequencies. J. Magn. Reson. 2011, 212, 204−215. (140) Saalwächter, K. Proton multi-quantum NMR for the study of chain dynamics and structural constraints in polymeric soft matter. Prog. Nucl. Magn. Reson. Spectrosc. 2007, 51, 1−35. (141) Morcombe, C. R.; Zilm, K. W. Chemical shift referencing in MAS solid state NMR. J. Magn. Reson. 2003, 162, 479−486. (142) Handbook of Ring-Opening Polymerization; Dubois, P., Coulembier, O., Raquez, J.-M., Eds.; Wiley-VCH: Weinheim, 2009. (143) Labet, M.; Thielemans, W. Synthesis of polycaprolactone: a review. Chem. Soc. Rev. 2009, 38, 3484−3504. (144) Ajellal, N.; Carpentier, J.-F.; Guillaume, C.; Guillaume, S.; Helou, M.; Poirier, V.; Sarazin, Y.; Trifonov, A. Metal-catalyzed immortal ring-opening polymerization of lactones, lactides and cyclic carbonates. Dalton Trans. 2010, 39, 8363−8376. (145) Nuyken, O.; Pask, S. Ring-opening polymerization−An introductory review. Polymers 2013, 5, 361−403. (146) Hodge, P. Entropically driven ring-opening polymerization of strainless organic macrocycles. Chem. Rev. 2014, 114, 2278−2312. (147) van der Meulen, I.; Gubbels, E.; Huijser, S.; Sablong, R.; Koning, C. E.; Heise, A.; Duchateau, R. Catalytic ring-opening polymerization of renewable macrolactones to high molecular weight polyethylene-like polymers. Macromolecules 2011, 44, 4301−4305. (148) Pepels, M. P. F.; Bouyahyi, M.; Heise, A.; Duchateau, R. Kinetic investigation on the catalytic ring-opening (co)polymerization of (macro)lactones using aluminum salen catalysts. Macromolecules 2013, 46, 4324−4334. (149) Pepels, M. P. F.; Soulje, P.; Peters, R.; Duchateau, R. Macromolecules 2014, 47, 5542−5550. (150) SEC analyses of amphiphilic block and graft copolymers can be misleading since the eluent is commonly not a good solvent for both blocks forming the block copolymer. Therefore, typically lower molecular weights are measured by HT-SEC than by HT solution NMR. (151) Strobl, G. Crystallization and melting of bulk polymers: New observations, conclusions and a thermodynamic scheme. Prog. Polym. Sci. 2006, 31, 398−442.

P


Toward Polyethylene–Polyester Block and Graft Copolymers with

Recommend Documents