Synthesis and Ring-Opening Metathesis Polymerization of

Article pubs.acs.org/Macromolecules

Synthesis and Ring-Opening Metathesis Polymerization of Norbornene-Terminated Syndiotactic Polypropylene Amelia M. Anderson-Wile and Geoffrey W. Coates* Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York, 14853-1301

Finizia Auriemma, Claudio De Rosa, and Amelia Silvestre Dipartimento di Chimica “Paolo Corradini”, Università di Napoli “Federico II”, Complesso di Monte S. Angelo, via Cintia, I-80126 Napoli, Italy S Supporting Information *

ABSTRACT: Using nonliving bis(phenoxyimine)titanium catalysts activated by methylaluminoxane (MAO) in the presence of propylene, allyl-terminated syndiotactic polypropylene macromonomers with varying tacticity ([rrrr] = 0.80 and 0.94) and molecular weight (Mn = 3600 and 5600 g/mol) were produced. The end-functionalized polymers were converted to hydroxyl- and subsequently norbornene-terminated macromonomers. Two series of syndiotactic polypropylene comb-polymers were synthesized through metathesis polymerization of the norbornene-functionalized polypropylene. The molecular weight (Mn = 46 000−172 000 g/mol) and polydispersity (Mw/Mn = 1.21−1.89) of the comb polymers was determined by gel permeation chromatography (GPC). Using differential scanning calorimetry (DSC), melting temperature (Tm) and crystallization temperature (Tc) were determined and both were observed to decrease with increasing conversion to poly(macromonomer). To the best of our knowledge, this is the first synthesis of comb-polymers from end-functionalized syndiotactic polypropylene.

■

INTRODUCTION The ability to control bulk polymer properties through manipulation of molecular weight, stereochemistry and polymer structure remains an overarching goal in the field of polymer chemistry. Over the last few decades, the development of single-site transition metal olefin polymerization catalysts has resulted in polyolefin materials with well-defined structures.1 Specifically, the production of polymers with high stereo- and regioregularity can give rise to materials with drastically improved properties.2 Another way to modify the observed properties of a polymeric material is to control the amount of branching in the system. The presence of even a small amount of long-chain branching in a polyolefin significantly alters properties such as processability and melt strength.3 For example, the incorporation of long-chain branches in polypropylene has been shown to increase the melt strength of the polymer up to ten times that of its linear analogue.4 Even minimal incorporation of long-chain branches in polyolefin materials has an effect on observed rheological properties,5 therefore, the investigation of highly branched polypropylene materials should be targeted. Comb polymers are a type of hyperbranched material which contain one long-chain branch per repeat unit of the polymer backbone.6 The high-density of polymer arms along the backbone often results in the material adopting a compact cylindrical shape as opposed to the more commonly observed spherical shape.7 Typical materials display lengths on the © 2012 American Chemical Society

nanometer scale making the polymers useful in applications such as nanotubes,8 nanocapsules9 or templates for inorganic nanowires.10 To synthesize comb polymers, one of three methods is typically employed.6a,c,7c In the “grafting onto” method, side-chains are prepared independently and then coupled to a functionalized polymer backbone.11 Although properties such as molecular weight are easily characterized with this method, steric crowding often precludes formation of a comb polymer with a high density of side-chains. Alternatively, the “grafting from” method employs a polymer backbone bearing initiating groups capable of polymerization as a basis for side-chain synthesis.7a,12,13 As with the previous method, a high density of side-chains is often difficult to obtain due to steric hindrance at the polymerization site. Furthermore, side-chain properties including molecular weight can be difficult to quantify. Finally, the “grafting through” or macromonomer method utilizes polymeric materials containing polymerizable functional groups.7b,c,12b,14 With this approach, side-chains can be thoroughly characterized prior to polymerization. Additionally, each repeat unit is guaranteed to contain a polymer sidechain, so truly high-density comb polymers can be synthesized. Although a high degree of polymerization can be challenging to obtain, techniques including controlled/living radical and ringReceived: May 25, 2012 Revised: August 13, 2012 Published: September 19, 2012 7863

dx.doi.org/10.1021/ma301073s | Macromolecules 2012, 45, 7863−7877

Macromolecules

Article

release through β-hydrogen or β-methyl transfers, which result in a number of alkene-terminated polymers. Most commonly, a 1,2-insertion of propylene into the growing polymer chain followed by β-hydrogen transfer gives vinylidene-terminated polypropylene, which would be less desirable for further endfunctionalization due to the steric bulk present at the alkene. Alternatively, β-methyl transfer from the same growing polymer chain results in allyl-terminated polypropylene, a much less sterically hindered macromonomer. A handful of metallocene catalysts have been observed to produce allyl end-groups following 1,2-propylene insertion, however, selectivities are at best 90% with vinylidenes making up the remaining chainends.23 In systems that are capable of 2,1 propylene insertion, β-hydrogen transfer could result in two different alkeneterminated polymers. Transfer of a β-hydrogen from the terminal methyl (β-Ha) results in an allyl-terminated polypropylene, whereas β-hydrogen transfer from the internal methylene (β-Hb) gives a polymer with a 2-propenyl endgroup. Complexes of both titanium24 and iron25 have been shown to undergo propylene polymerization in a 2,1 fashion with subsequent β-hydrogen transfer resulting in polypropylene with terminal allyl groups. In fact, when 2,1-insertion dominates propylene polymerization, terminal allyl groups are almost exclusively observed.24 Many alkene-terminated polypropylenes have served as useful synthetic intermediates in the production of polymers with alternative functional groups, such as alcohols and amines.22 End-functionalized polymers are attractive building blocks for the synthesis of more complex architectures such as block copolymers26 and star polymers.27 Upon activation with methylaluminoxane (MAO), bis(phenoxyimine)titanium catalysts polymerize propylene in a 2,1 fashion to produce highly syndiotactic polypropylene (Scheme 2).24,28 Extensive ligand modification has been carried

opening metathesis (ROMP) have been employed in the synthesis of comb polymers.7,12,15 In particular, Bowden and co-workers have reported the successful production of several ultrahigh molecular weight comb homopolymers and comb block copolymers containing polystyrene, polynorbornene and polylactide.7a,12,15,16 Therefore, we utilized the macromonomer method to produce branched, high molecular weight polypropylene comb polymers. Despite a significant amount of research in this area,7−14 there are relatively few examples of comb polymers produced from the polymerization of polypropylene based macromonomers. In 2008, we reported the homopolymerization of allyl-terminated poly(ethylene-co-propylene) using a living nickel α-diimine catalyst, which resulted in star-like polymers containing up to 16 branches per sample.17 Because of a low degree of polymerization, these polymers possessed star-like conformations in dilute solutions instead of the rigid rod structure that would be expected for higher molecular weight comb polymers. In another example employing end-functionalized polymers, Kaneko et al. utilized methacryloyl terminated poly(ethylene-co-propylene) in free radical copolymerizations with methyl methacrylate.18 With this method, graft and star copolymers were produced containing poly(methyl methacrylate) backbones and poly(ethylene-co-propylene) branches. Alternatively, the homopolymerization of semicrystalline polypropylene macromonomers (syndiotactic or isotactic) has been more difficult to achieve due in part to lower solubility compared with poly(ethylene-co-propylene) macromonomers. To synthesize semicrystalline polypropylene comb-polymers, syndiotactic polypropylene bearing a highly reactive, polymerizable functional group at the terminus was required. Specifically, a norbornene-terminated polypropylene was targeted due to previous reports of high reactivity with ringopening metathesis polymerization catalysts for the synthesis of poly(macromonomer)s.7,12 End-functionalized polyolefins may be produced using a variety of different methods including living19 and nonliving20 transition metal catalysis, chain transfer polymerization,21 and thermal degradation,22 which can result in difunctional and nonfunctional polymers in addition to the desired monofunctional polymers. Of particular interest are nonliving transition metal olefin polymerization catalysts because of their ability to produce multiple polymer chains per metal center without the addition of a chain transfer agent (Scheme 1).1b Nonliving olefin polymerization catalysts are known to undergo chain-

Scheme 2. Synthesis of Allyl-Terminated Syndiotactic Polypropylene Using Non-Living Bis(phenoxyimine) titanium Catalysts

Scheme 1. Olefin Polymerization Chain-Transfer Pathways

out, and studies have shown the fluorination pattern of the Naryl ring has a significant effect on the nature of the polymerization.24,28j,p With at least one fluorine present in the ortho position of the N-aryl ring, bis(phenoxyimine)titanium complexes catalyze the living polymerization of propylene resulting in polypropylene with completely saturated end-groups upon quenching with a protic electrophile.28h,i However, when all fluorines are removed from the ortho position of the N-aryl ring as in complexes 1 and 2, the subsequent propylene polymerization is no longer living and the dominant chain termination pathway is β-hydrogen transfer.24,28a The 1H NMR spectrum of the polypropylene produced from nonliving bis(phenoxyimine)titanium catalysts 7864


Macromolecules

Article

precipitated into a copious amount of acidic methanol (5% HClaq) and stirred overnight. The polymer was isolated and rinsed with methanol. To purify the sample, the polymer was dissolved in hot toluene and filtered through a glass frit layered with silica, alumina, and Celite. The toluene was removed and the polymer was dried in vacuo to constant weight. For MM-3600 from catalyst 1, yield = 9.11 g, Mn(GPC) = 3600 g/mol, and Mw/Mn = 1.87, Mn(1H NMR) = 5800 g/mol. For MM-5600 from catalyst 2, yield = 8.5 g. Mn(GPC) = 5600 g/mol, and Mw/Mn = 1.75, Mn(1H NMR) = 7400 g/mol. 1H NMR (600 MHz, C2D2Cl4, 135 °C): δ 5.81 (dd, 1H), 5.01 (m, 2H), 1.72−0.68 (m, 800H (MM-3600), 1100H (MM-5600)). Hydroxyl-Terminated Syndiotactic Polypropylene.19b An ovendried 1 L round-bottom flask was cooled under vacuum and charged with allyl-terminated syndiotactic polypropylene (1 mmol). THF (500 mL, MM-3600) or toluene (500 mL, MM-5600) was cannulated into the flask and the mixture was heated to 45 °C. After 15 min, the 9BBN (7 mL, 3.5 mmol) was added dropwise to the flask and the solution was heated to 65 °C. The mixture was cooled to 45 °C after 3 h. A sodium hydroxide solution (1.5 M in H2O, 15 mmol) was added followed immediately by a hydrogen peroxide solution (1.22 M in THF, 11 mmol). After 2 h, the mixture was poured into copious methanol. The polymer was collected, dissolved in hot toluene and filtered through a glass frit layered with silica, alumina, and Celite. The toluene was removed and the polymer was dried in vacuo to constant weight. For MM-3600, yield = 5.8 g, conversion = 92%, Mn(GPC) = 3700 g/mol, Mw/Mn = 1.90, and Mn(1H NMR) = 6300 g/mol. For MM-5600, yield = 7.0 g, conversion = 60%, Mn(GPC) = 5600 g/mol, and Mw/Mn = 1.74, Mn(1H NMR) = 13 000 g/mol. 1H NMR (600 MHz, C2D2Cl4, 135 °C): δ 3.61 (q, 2H), 1.72−0.68 (m, 900H (MM3600),1850H (MM-5600)). Norbornene-Terminated Syndiotactic Polypropylene. An ovendried Schlenk adapted round-bottom flask was cooled under vacuum and charged with exo-5-norbornene-2-carboxylic acid ((1R,2S,4R)bicyclo[2.2.1]hept-5-ene-2-carboxylic acid, 0.35 mL, 2.5 mmol) and toluene (10 mL). Oxalyl chloride (0.22 mL, 2.5 mmol) was slowly syringed into the tube at room temperature. The mixture was warmed to 70 °C for 2 h. The solution was then cooled to room temperature and the solvent was removed in vacuo. Additional dry toluene (250 mL), hydroxyl-terminated syndiotactic polypropylene (0.5 mmol) and triethylamine (0.35 mL, 2.5 mmol) were added to the flask and the mixture was heated to 70 °C. After 12 h, the solution was cooled to room temperature and the polymer was precipitated with copious methanol. The polymer (exo-MM-3600 or exo-MM-5600) was collected, dissolved in hot toluene and filtered through a glass frit layered with silica, alumina, and Celite. The toluene was removed and the polymer was dried in vacuo to constant weight. For exo-MM-3600, yield =2.8 g, conversion = 75%, Mn(GPC) = 3600 g/mol, Mw/Mn = 1.87, and Mn(1H NMR) = 8400 g/mol. For exo-MM-5600, yield = 3.4 g, conversion = 93%, Mn(GPC) = 5600 g/mol, Mw/Mn = 1.75, and Mn(1H NMR) = 14 000 g/mol. 1H NMR (600 MHz, C2D2Cl4, 135 °C): δ 6.18 (m, 2H), 4.13 (t, 2H), 3.10 (s, 1H), 2.95 (s, 1H), 2.27 (m, 1H), 1.98 (m, 2H), 1.72−0.80 (m, 1200H (MM-3600), 2000H (MM5600)). Poly(macromonomer) Synthesis. Polymerization of exo-MM3600 and exo-MM-5600 with 3, 4, or 5. A 20 mL scintillation vial was charged with norbornene-terminated polypropylene (0.042 mmol). A prescribed amount of 3, 4, or 5 in toluene (1.65−0.42 mM) was syringed into the vial. The mixture was diluted with desired amount of toluene (0.5−5.0 mL) and heated to 60 or 80 °C for a given amount of time. Ethyl vinyl ether and additional toluene were added to the vial and the mixture was reheated to quench the polymerization and dissolve the poly(macromonomer). After 1 h, the polymer was precipitated with copious methanol and collected. Typical polymerizations resulted in over 90% recovery of polymer (>0.22 g). The poly(exo-MM-3600) obtained from 3 was dissolved in hot THF, cooled to −30 °C for 24 h, filtered, collected and dried in vacuo to constant weight. Poly(exo-MM-5600) was dissolved in hot toluene, filtered hot, collected and dried in vacuo to constant weight. 1H NMR (600 MHz, C2D2Cl4, 135 °C): δ 5.58−5.19 (m), 4.21−3.98 (m), 2.89−2.46 (m), 2.21−1.98 (m), 1.72−0.68 (m).

reveals only allyl-termination, with no vinylidene or internal alkenes observed.24 The syndiotactic polypropylene produced in this fashion is ideal for this study due to a low degree of steric hindrance at the chain-end. Herein, we report the synthesis and ring-opening metathesis polymerization of norbornene-terminated syndiotactic polypropylene macromonomers. Polymers of varying molecular weights were produced from two different bis(phenoxyimine) titanium catalysts (1 and 2). Hydroxyl and norbornene endfunctionalized polypropylene were obtained from the allylterminated polymer. Subsequent ring-opening metathesis polymerization reactions were carried out using ruthenium catalysts (3−5), resulting in the production of a new class of high molecular weight, syndiotactic comb polymers.

■

EXPERIMENTAL SECTION

General. All manipulations of air- and/or water-sensitive compounds were carried out under dry nitrogen using Braun UniLab drybox or standard Schlenk techniques. Toluene was purified over columns of alumina and copper (Q5). THF was purified over an alumina column and degassed by three freeze−pump−thaw cycles before use. Propylene (Airgas, research purity) was purified over columns (40 cm inner diameter x 120 cm long) of BASF catalyst R3− 12, BASF catalyst R3−11, and 4 Å molecular sieves. PMAO-IP (13 wt % Al in toluene, Akzo Nobel) was dried in vacuo to remove residual trimethyl aluminum and used as a solid white powder. Complexes 1 and 2 were prepared according to previously reported procedures.23 Triethylamine was stirred over CaH2 for several days and vacuum distilled. Oxalyl chloride, 0.5 M 9-borabicylo[3.3.1]nonane (9-BBN) in THF, exo-5-norbornene-2-carboxylic acid, Cl2(Cy3P)2RuCHPh (3, Grubbs’ first generation catalyst), Cl2(Cy3P)(H2IMes)RuCHPh (4, Grubbs’ second generation catalyst), and Cl2(3-BrC5H5N)2(H2IMes)RuCHPh (5) were purchased from commercial sources and used as received. Polymer Characterization. 1H and 13C{1H} NMR spectra of polymers were recorded using a Varian UnityInova (600 MHz) spectrometer equipped with a 1H/BB switchable with Z-pulse field gradient probe operating and referenced versus residual nondeuterated solvent shifts. The polymer samples were dissolved in 1,1,2,2tetrachloroethane-d2 in a 5 mm o.d. tube, and spectra were collected at 135 °C. End-group analysis for molecular weight determination was achieved by relative integration of the end-group vs alkyl peaks in the 1 H NMR spectrum. Percent conversion was determined through relative integration of the macromonomer alkene resonance to the poly(macromonomer) alkene resonances in the 1H NMR spectrum. Syndiotacticity ([rrrr]) was measured by Gaussian deconvolution of the methyl region of the 13C NMR spectrum. Molecular weights (Mn and Mw) and polydispersities (Mw/Mn) were determined by high temperature gel permeation chromatography (GPC). Analyses were performed with a Waters Alliance GPCV 2000 GPC equipped with a Waters DRI detector and viscometer. The column set (four Waters HT 6E and one Waters HT 2) was eluted with 1,2,4-trichlorobenzene containing 0.01 wt % di-tert-butyl-hydroxytoluene (BHT) at 1.0 mL/ min at 140 °C. Data were calibrated using monomodal polyethylene standards (from Polymer Standards Service). Differential scanning calorimetric analyses were performed in crimped aluminum pans under nitrogen using a TA Instruments Q1000 calorimeter equipped with an automated sampler. Data were collected from the second heating run at a heating rate of 10 °C/min from −50 to +200 °C and were processed with the TA Q series software package. Macromonomer Synthesis. Allyl-Terminated Syndiotactic Polypropylene. In a glovebox, a 12 oz Laboratory Crest reaction vessel (Andrews Glass) was charged with dried PMAO (1.15 g, 19.8 mmol) and toluene (300 mL). The vessel was purged with propylene gas three times and equilibrated at 0 °C and 30 psig propylene for 30 min. A solution of the Ti precatalyst (100 μmol, [Al]/[Ti] = 200) in toluene (10 mL) was injected into the reactor. After 9 h, the reaction mixture was quenched with methanol (10 mL) and the polymer was 7865


Macromolecules

Article

Table 1. Syndiotactic Polypropylene Macromonomer Characterization macromonomer

complex

R1

R2

Mn (g/mol)a

Mw/Mna

[rrrr]b

Tc (°C)c

Tm (°C)c

ΔH (J/g)c

MM-3600 MM-5600

1 2

tBu SiMe3

tBu H

3600 5600

1.87 1.75

0.80 0.94

72 109

113 145

40 70

Molecular weight (Mn) and molecular weight distribution (Mw/Mn) were determined by gel permeation chromatography at 140 °C in 1,2,4trichlorobenzene relative to polyethylene standards. bSyndiotacticity ([rrrr]) was determined using 13C NMR spectroscopy. cMelting temperature (Tm), crystallization temperature (Tc), and enthalpy (ΔH) were determined by differential scanning calorimetry (second heating run). a

Isothermal Crystallization. To perform a more detailed characterization of the crystallization behavior of the norborneneterminated syndiotactic polypropylene macromonomer and the corresponding poly(macromonomer), the structure, the melting behavior and the kinetics of crystallization in isothermal conditions of selected samples were also investigated. A larger quantity of poly(macromonmer) was required and a new batch of macromonomer (exo-MM3600-80, where 80 indicates the percentage of rrrr pentads and exo indicates the presence of the exo-norbornene moiety) was synthesized using catalyst 1 and the procedure described above. Polymerization with catalyst 3 was carried out on 2 g of exo-MM-3600 and the corresponding poly(macromonomer) (PM-3600-80) was obtained (see Supporting Information for the scaled up procedure). The samples obtained from the scaled up procedure were isothermally crystallized from the melt at different temperatures. Asprepared samples were melted at 200 °C and kept for 5 min at this temperature in a N2 atmosphere; they were then rapidly cooled to the crystallization temperature (Tc) and kept at this temperature, still in a N2 atmosphere, for a time (tc) long enough to allow complete crystallization at Tc. The samples were then rapidly cooled to room temperature and analyzed by X-ray diffraction and DSC. In the various isothermal crystallizations, the crystallization time (tc) is different depending on the crystallization temperature. The shortest time was about 2 h for the lowest crystallization temperature and increases with increasing the crystallization temperature, up to 8−10 h for the highest crystallization temperature. The kinetics of crystallization from the melt of the sPP macromonomer exo-MM-3600-80 and the corresponding polymacromonomer PM-3600-80 were also studied by performing meltcrystallizations at different temperatures in a differential scanning calorimeter Mettler Toledo DSC 1 in flowing N2 atmosphere. Melt crystallized samples obtained by compression molding were melted at 200 °C at heating rate of 2.5 °C/min; they were then cooled to the crystallization temperature (Tc) at rate of 20 °C/min and kept at this temperature, still in a N2 atmosphere, for a time (tmax) long enough up to achieve complete crystallization at the given Tc, while recording the crystallization enthalpy ΔHc(t) as a function of time. We have checked that the selected values of Tc in our isothermal crystallization experiments were high enough to prevent crystallization of sPP chains during the cooling step of the melt at rate of 20 °C/min before reaching the Tc. The samples were then heated from Tc up to 200 °C at heating rate of 2.5 °C/min, and the melting enthalpy ΔHm(tmax) of the material crystallized at the temperature Tc during the time tmax was recorded. The apparent degree of crystallinity x′c(t) was calculated as a function of the crystallization time from the crystallization enthalpy ΔHc(t) as x′c(t) = ΔHc(t)/ΔHc∞, with ΔHc∞ being the total crystallization enthalpy. In all cases, the total crystallization enthalpy ΔHc∞ recorded at any Tc was numerically coincident (in absolute value) with the melting enthalpy ΔHm(tmax) recorded during the successive heating scan. The corresponding degree of crystallinity xc(tmax) was then calculated as xc(tmax) = ΔHm(tmax)/ΔHm° with ΔHm° being the thermodynamic melting enthalpy of sPP assumed equal to 190 J/g.29 The upper bound value of 190 J/g has been used for ΔHm° instead of the lower bound value of 75 J/g proposed in ref 30, also in agreement with the unbiased analysis of thermodynamic melting parameters of sPP performed by Supaphol et al. in ref 31. Additional DSC data were also obtained at heating rate of 10 °C/min. To improve the signal-to-noise ratio of DSC curves recorded during the isothermal crystallizations as a function of time, some experiments, especially those conducted at high Tc, were repeated over at least 3

independent specimens. The corresponding DSC curves obtained during the crystallization step were then averaged and the so obtained curve was smoothed using the fast-Fourier-transform filter of the software Origin 7.0. X-ray powder diffraction profiles were obtained with Ni filtered Cu Kα radiation using an automatic Philips diffractometer by performing a continuous scan at rate of 0.1°(Δ2θ)/5s. Crystallinity (xc(WAXS)) was determined from the powder diffraction profiles by the ratio between the crystalline diffraction area (Ac) and the area of the whole diffraction profiles (At), xc = (Ac/At) × 100. The area of the crystalline diffraction Ac was evaluated by subtracting the area of the amorphous halo from the area of the whole diffraction profiles At. The diffraction profiles of the amorphous phase was constructed by collecting X-ray powder diffraction profiles of melted samples in the temperature range 150−180 °C, and by successive extrapolation of these data to room temperature, in order to account for the thermal expansion of amorphous/molten state.

■

RESULTS AND DISCUSSION Synthesis of Syndiotactic Polypropylene Macromonomer. Activation of bis(phenoxyimine) titanium complexes 1 and 2 with MAO in the presence of propylene resulted in polymer with modest molecular weight (Table 1, Mn = 3600 and 5600 g/mol, respectively).24 Bis(phenoxyimine) titanium complexes bearing hydrogens in the ortho-positions of the Naryl ring have previously been shown to insert propylene in a 2,1 fashion with subsequent chain transfer reactions resulting in alkene-terminated polypropylyene.24 Because of the 2,1insertion mechanism (Scheme 1), propenyl- as well as allylterminated polymer could be produced from β-hydrogen transfer. Examination of the polypropylene 1H NMR spectrum (Figure 1) revealed resonances at δ 5.81 and 5.01 ppm, which have been assigned to the allyl functional group. Further analysis shows no resonance at δ 5.5, which would be indicative of the 2-propenyl end-group. Using 13C NMR spectroscopy to analyze the polymer microstructure, a range of tacticities were observed from moderately ([rrrr] = 0.80) for the polypropylene produced by 1 (MM-3600) to highly syndiotactic ([rrrr] =

Figure 1. 1H NMR spectra of sPP-allyl, sPP-hydroxyl, and sPPnorbornene (MM-3600, 600 MHz, 1,1,2,2-tetrachloroethane-d2, 135 °C). 7866


Macromolecules

Article

creased reaction rates, as well as molecular weights for the polymerization endo-/exo-norbornene-terminated polylactide macromonomers compared with the exo-norbornene-terminated polylactide macromonomer.12b Therefore, the synthesis and subsequent polymerization behavior of exo-norborneneterminated syndiotactic polypropylene was investigated. Starting from exo-5-norbornene-2-carboxylic acid, transformation of the carboxylic acid to the acid chloride was achieved with oxalyl chloride in toluene at 70 °C. The resultant acid chloride was combined with the hydroxyl-terminated syndiotactic polypropylene in the presence of triethylamine and toluene at 100 °C. The exo-norbornene-terminated syndiotactic polypropylene macromonomers (exo-MM-3600 and exo-MM-5600) were produced utilizing the polymers obtained from catalyst 1 and 2. 1H NMR analysis of the exo-norbornene-terminated polymer (Figures 1 and S3, Supporting Information) revealed a single resonance in the alkene region (δ 6.18), a signal attributed to the protons adjacent to the ester (δ 4.13) as well as four new resonances for the norbornene ring (δ 3.10, 2.95, 2.27, and 1.98 ppm).32 Through facile organic transformations, syndiotactic polymers bearing norbornene groups at the terminus have been produced. Polymerization of Norbornene-Terminated Syndiotactic Polypropylene. Initial investigations into the polymerization behavior of the norbornene-terminated syndiotactic polypropylene were carried out with the lower tacticity, more soluble macromonomer, exo-MM-3600, and a series of metathesis catalysts (Figure 2). All three of the ruthenium

0.94) for the polymer obtained from 2 (MM-5600). As a result, the polymers displayed a range of melting temperatures (Tm = 113 and 145 °C) as determined by differential scanning calorimetry. Fortunately, the semicrystalline polymers produced by 1 and 2 are soluble in many solvents making a variety of organic transformations possible. The terminal alkene moiety was utilized as a synthetic handle for the production of end-functionalized polypropylene bearing functional groups with increased reactivity. The allyl-functionalized polypropylene can easily be converted to primary hydroxyl-terminated polypropylene using hydroboration-oxidation (Scheme 3). In 2005, Hagiwara and co-workers reported Scheme 3. Synthesis of Norbornene-Terminated Syndiotactic Polypropylene

the conversion of vinylidene-terminated polypropylene formed through controlled thermal degradation to the primary alcohol using a borane-THF complex and subsequent hydrogen peroxide oxidation.19b Conversion of the vinylidene to the hydroxyl end-group was achieved in greater than 90% yields for most of the polymers utilized in their study. Using a similar procedure, the allyl-terminated syndiotactic polypropylene produced with 1 and 2 was converted to the hydroxylfunctionalized polymer using 9-BBN at 65 °C followed by the addition of sodium hydroxide and hydrogen peroxide. Analysis of the 1H NMR spectrum (Figure 1) showed complete disappearance of the alkene resonances and the appearance of a new resonance (δ 3.61) for the protons on the methylene adjacent to the hydroxyl and is consistent with literature reports for hydroxyl-terminated polymers.19b Conversion to product was dependent on the solvent, time and temperature at which the oxidation was performed. For the allyl-terminated syndiotactic polypropylene produced from 1, carrying the hydroboration out at 60 °C in THF followed by oxidation at 45 °C resulted in high conversion to hydroxyl-terminated polypropylene (92%). Because of lower solubility of the highly syndiotactic polymer produced from 2, the hydroborationoxidation was carried out in toluene, resulting in slightly lower conversion to hydroxyl-terminated polymer (60%). Installing the primary hydroxyl group on the end of the polypropylene chain resulted in an end-functionalized polymer, which was useful for the production of a syndiotactic polypropylene macromonomer. In particular, reaction of the hydroxyl-terminated polypropylene with acid chlorides was facile and was therefore utilized to produce polymerizable macromonomers. Ringopening metathesis polymerization of norbornene-terminated macromonomers has been achieved by a number of research groups to obtain high molecular weight poly(macromonomer)s.7,12,15 Specifically, Bowden and co-workers observed de-

Figure 2. Grubbs’ olefin metathesis polymerization catalysts for poly(macromonomer) preparation.

complexes screened (3−5) resulted in high conversion of macromonomer to poly(macromonomer) (>94%) in just 2 h (Table 2, Scheme 4). The poly(macromonomer)s obtained from 4 and 5 both displayed a high peak molecular weight (Mp = 73 000 and 64 000 g/mol, respectively), but the overall molecular weight (Mn = 35 000 and 36 000 g/mol) was considerably lower. Furthermore, molecular weight distributions (Mw/Mn = 2.00 and 2.11) were broader than those observed for the poly(macromonomer) (Mw/Mn = 1.25) derived from 3, which also displayed the highest molecular weight (Mn = 77 000 g/mol). Additionally, molecular weight distribution of the poly(macromonomer) obtained from 3 was lower than the starting macromonomer (Mw/Mn = 1.87). This is consistent with star polymer theory laid out by Schulz and Flory, which suggests that polymer molecular weight distribution will decrease as the number of arms linked together increases.33 Analysis of the poly(macromonomer) by GPC reveals a very small low molecular weight shoulder, which can be attributed to a small amount of unfunctionalized polypropylene present in the starting macromonomer. This was confirmed by analysis of the 1H NMR spectra, which showed the disappearance of the alkene resonances associated with the 7867


Macromolecules

Article

Table 2. Metathesis Polymerization of exo-MM-3600 at 60 °C entry a

1 2b 3a

complex

trxn (h)

convn (%)c

Mn (g/mol)d

Mp (g/mol)d

Mw/Mnd

Tc (°C)e

Tm (°C)e

ΔH (J/g)e

3 4 5

2 2 2

94 >99 >99

76 000 35 000 36 000

83 000 73 000 64 000

1.25 2.00 2.11

50 42 43

104 105 105

31 36 40

a General conditions: [MM-3600]o = 0.083 M, [Ru] = 1.65 mM, [MM-3600]:[Ru] = 50:1. b[MM-3600]o = 0.0083 M, [Ru] = 0.165 mM, [MM3600]:[Ru] = 50:1. cDetermined using 1H NMR spectroscopy in 1,1,2,2-tetrachloroethane-d2 at 135 °C. dMolecular weight (Mn), peak molecular weight (Mp) and molecular weight distribution (Mw/Mn) were determined by gel permeation chromatography at 140 °C in 1,2,4-trichlorobenzene relative to polyethylene standards. eMelting temperature (Tm), crystallization temperature (Tc), and enthalpy (ΔH) were determined by differential scanning calorimetry (second heating run).

Scheme 4. Ring-Opening Metathesis Polymerization (ROMP) of Norbornene-Terminated Syndiotactic Polypropylene

norbornene-terminated syndiotactic polypropylene. Homopolymerization of the norbornene-terminated polymer was possible with the three different ruthenium metathesis catalysts that were screened. On the basis of these initial screening results, 3 was identified as the best catalyst for ring-opening metathesis polymerization of the syndiotactic polypropylene macromonomers. The polymerization rate of 3 (Table 3) was further investigated because of its ability to produce the highest molecular weight polymer with the narrowest polydispersity. After just 3 min, 59% conversion to comb polymer was observed through analysis of the poly(macromonomer) 1H NMR spectrum. In addition to the residual macromonomer, a higher molecular weight peak (Mp = 65 000 g/mol) attributed to the poly(macromonomer) was observed (Figure 3). Because of overlapping macromonomer and poly(macromonomer) peaks in the GPC chromatogram, it is useful to compare peak molecular weights here. Upon increasing reaction time to 6 min, greater conversion (67%) and higher peak molecular weight (Mp = 73 000 g/mol) were obtained in addition to residual macromonomer. After 10 min, 87% conversion of macromonomer to comb polymer was observed (Mp = 75 000

Figure 3. GPC chromatogram of ROMP polymerization of exo-MM3600 using 3 after 3 (green, entry 1, Table 3), 10 (blue, entry 3, Table 3) and 120 min (pink, entry 4, Table 3).

g/mol) along with a decreased amount of macromonomer. When reaction time was extended to 2 h, nearly complete conversion (94%) was obtained as evidenced by 1H NMR spectroscopy. Furthermore, molecular weight increased (Mp = 83 000 g/mol, Mn = 76 000 g/mol) and residual macromonomer was no longer present in the GPC chromatogram. Allowing the reaction to proceed for a full 24 h resulted in quantitative conversion of macromonomer to poly(macromonomer) (>99%) with the highest molecular weight (Mp = 98 000 g/mol, Mn = 86 000 g/mol) observed. Comparing the molecular weight data by GPC (Figure 3) reveals that the polymerization proceeds quickly up to 10 min. Extended reaction times are required to obtain higher

Table 3. Metathesis Polymerization of exo-MM-3600 with 3 at 60 °Ca entry

trxn (min)

convn (%)b

Mn (g/mol)c

Mp (g/mol)c

Mw/Mnc

Tc (°C)d

Tm (°C)d

ΔHc (J/g)d

1 2 3 4 5

3 6 10 120 1440

59 67 87 94 >99

11 000 12 000 12 000 76 000 86 000

65 000 73 000 75 000 83 000 98 000

3.90 (bm)e 4.25 (bm)e 4.55 (bm)e 1.24 1.21

59 59 53 50 45

110 109 106 104 104

35 42 29 31 24

a General conditions: [MM-3600]o = 0.083 M, [Ru] = 1.65 mM, [MM-3600]:[Ru] = 50:1. bDetermined using 1H NMR spectroscopy in 1,1,2,2tetrachloroethane-d2 at 135 °C. cPeak molecular weight (Mp), molecular weight (Mn) and molecular weight distribution (Mw/Mn) were determined by gel permeation chromatography at 140 °C in 1,2,4-trichlorobenzene relative to polyethylene standards. dMelting temperature (Tm), crystallization temperature (Tc), and enthalpy (ΔH) were determined by differential scanning calorimetry (second heating run). eBimodal due to presence of exoMM-3600.

7868


Macromolecules

Article

and crystallization temperature decreased with comb-polymer formation. The decrease in melting and crystallization temperatures with increasing degree of polymerization suggests that the mobility of the sPP chains in the poly(macromonomer) also decreases. However, the differences in melting and crystallization temperature may also be due to changes in the cis:trans ratio of double bonds along the comb-polymer backbone which may vary with the catalyst35 or as a function of conversion.36 The geometry of the double bonds in the poly(norbonene) chain of the poly(macromonomer) would alter the sterics of the system and may indeed explain the observed decrease in crystallization temperature for the combpolymers obtained at different conversions or with different catalysts. To test the limits of macromonomer polymerization, the two norbornene-terminated syndiotactic polypropylene macromonomers (exo-MM-3600 and exo-MM-5600) were polymerized with 3 at a variety of catalyst loadings (Table 4). Polymerization of exo-MM-3600 at low catalyst loadings (50:1, [MM]o: [Ru]) resulted poly(macromonomer) (Mn = 86 000 g/mol, Mw/Mn = 1.21) with little residual macromonomer and high conversion (>99%) observed. Comparatively, poly(macromonomer) with modest molecular weight (Mn = 46 000 g/mol, Mw/Mn = 1.89) was obtained upon polymerization of exo-MM-5600 at low catalyst loadings (50:1, [MM]o:[Ru]). Tapering of the peaks observed by GPC (Figure S11, Supporting Information) has been attributed to residual unfunctionalized macromonomer. This was confirmed through analysis of the 1H NMR spectra, which revealed high conversion of the norbornene-terminated polymer to combpolymer (>99%). Decreasing the catalyst loading (200:1, [MM]o:[Ru]) resulted in the high conversion (95%) of exoMM-3600 to comb polymer (Mn = 136 000 g/mol) with very little low molecular weight polymer observed by GPC. Polymerization of exo-MM-5600 under the same conditions (200:1, [MM]o:[Ru]) also resulted in high conversion (>99%) to comb polypropylene (Mn = 105 000 g/mol, Mw/Mn = 1.33). In an attempt to obtain an even higher molecular weight, catalyst loadings (500:1, [MM]o:[Ru]) were decreased still further, and polymerization of exo-MM-3600 resulted in a poly(macromonomer) with Mn = 172 000 g/mol and Mw/Mn = 1.29. An increased amount of residual macromonomer by GPC (Mn = 4800 g/mol) and lower conversion (88%) by 1H NMR spectroscopy were observed compared with higher catalyst loadings. Using the same reaction conditions (500:1, [MM]o: [Ru]), poly(macromonomer) (Mn = 120 000 g/mol, Mw/Mn = 1.30) was obtained from the polymerization of exo-MM-5600. Similar to exo-MM-3600, an increased amount of residual

conversions which may be attributed to the lower solubility and concentration of the macromonomer or alternatively the decreased activity of the ruthenium catalyst (3) over time.34 Formation of comb polymer is also confirmed by comparison of the poly(macromonomer) alkene region of the 1H NMR spectra (Figure 4). After 3 min, macromonomer is observed, as

Figure 4. 1H NMR spectra of poly(MM-3600) produced with 3 after 3 (entry 1, Table 3), 10 (entry 3, Table 3) and 120 (entry 4, Table 3) min (600 MHz, 1,1,2,2-tetrachloroethane-d2, 135 °C).

evidenced by the multiplet at δ 6.18, and broad resonances at δ 5.58−5.19 ppm are indicative of the presence of the combpolymer. Increasing reaction time to 10 min reveals further conversion to poly(macromonomer) with decreased macromonomer observed. At 2 h, very little macromonomer is present in the 1H NMR spectrum indicating nearly complete conversion to poly(macromonomer). In addition to GPC and 1H NMR spectroscopy, the extent of polymerization was also assessed through analysis of the combpolymer thermal data (Table 3) obtained from differential scanning calorimetry. Compared with exo-MM-3600 (Tm = 112 °C), a decrease in the melting temperature was observed for poly(macromonomer) obtained after 2 h (Tm = 104 °C). Furthermore, melting temperature was also observed to decrease as a function of conversion with Tm = 110, 109, and 106 °C obtained after three, six and 10 min, respectively. As with melting temperature, crystallization temperature was also observed to decrease with increasing conversion of macromonomer (Tc = 73 °C) to comb-polymer (Tc = 59−45 °C) with the lowest crystallization temperature observed for the highest conversion to poly(macromonomer). At varying reaction times, the polymerization of exo-MM-3600 with 3 resulted in poly(macromonomer) with molecular weights observed to increase over time while both melting temperature

Table 4. Polymerization of exo-MM-3600 and exo-MM-5600 with 3a entry

macromonomer

[MM]o:[Ru]

Trxn (°C)

convn (%)b

Mn (g/mol)c

Mw/Mnc

Tc (°C)d

Tm (°C)d

ΔH (J/g)d

1 2 3 4 5 6

exo-MM-3600 exo-MM-3600 exo-MM-3600 exo-MM-5600 exo-MM-5600 exo-MM-5600

50:1 200:1 500:1 50:1 200:1 500:1

60 60 60 80 80 80

>99 95 88 >99 >99 93

86 000 136 000 172 000 46 000 105 000 120 000

1.21 1.31 1.29 1.89 1.33 1.30

45 44 47 104 102 98

104 104 106 135 135 135

24 28 18 57 64 44

a

General conditions: [MM-3600]o = 0.083 M, [Ru] = 0.165−1.65 mM, trxn = 24 h. bDetermined using 1H NMR spectroscopy in 1,1,2,2tetrachloroethane-d2 at 135 °C. cMolecular weight (Mn) and molecular weight distribution (Mw/Mn) were determined by gel permeation chromatography at 140 °C in 1,2,4-trichlorobenzene relative to polyethylene standards. dMelting temperature (Tm), crystallization temperature (Tc), and enthalpy (ΔH) were determined by differential scanning calorimetry (second heating run). 7869


Macromolecules

Article

°C) was more prominent than the second endotherm for all poly(macromonomer)s studied (Figure S10, Supporting Information) suggesting that immediate recrystallization is suppressed and/or slowed down with the formation of comb polymer. Further analysis of the DSC data reveals the crystallization temperature follows a similar trend. Formation of poly(exo-MM-3600) resulted in decreased crystallization temperatures (Tc = 44−47 °C) compared with exo-MM-3600 (Tc = 73 °C). Analogously, decreased crystallization temperatures (Tc = 98−104 °C) were observed for poly(exo-MM5600) compared with exo-MM-5600 (Tc = 109 °C). For both syndiotactic polypropylene macromonomers, melting temperature and crystallization temperature were found to decrease with the formation high molecular weight poly(macromonomer). It is worth noting that the observed reduction of crystallization temperature with respect to the macromonomer is ≈30 °C in the case of poly(exo-MM-3600) and only 5−10 °C for poly(exo-MM-5600). This difference may be due to the different lengths of the sPP branches. In fact, in densely branched poly(macromonomers), adjacent side chains experience mutual repulsions mainly in the regions close to the backbone and these repulsive interactions result in a reduction of their mobility and also of their crystallization ability. However, since these interactions gradually fade away in regions far from the backbone, it is expected that long branches recover their degree of freedom almost completely at distance higher than their intrinsic persistence length from the backbone.6g,38 Preliminary Characterization Data of NorborneneTerminated Syndiotactic Polypropylene Macromonomers vs Corresponding Poly(macromonomer). In order to unravel the possible origin of the decrease of melting and crystallization temperatures of norbornene-terminated syndiotactic polypropylene macromonomers upon formation of the high molecular mass poly(macromonomer), further investigations were carried using the exo-MM-3600 macromonomer (sample exo-MM-3600-80) and the corresponding poly(macromonomer) (sample PM-3600-80, Mn = 100 000 g/ mol, Mw/Mn = 1.27, Table S1, Supporting Information) with a high molecular mass. In particular, the crystallization behavior and kinetics of these samples were probed in isothermal conditions. The X-ray powder diffraction profiles of the macromonomer exo-MM-3600-80 and the corresponding poly(macromonomer) PM-3600-80 are compared in Figure 6 with both the as-prepared samples and samples obtained by isothermal crystallization from the melt at various temperatures (Tc) shown. The X-ray powder diffraction profiles of as synthesized macromonomer and corresponding poly(macromonomer) are similar. Both samples crystallize in the antichiral form I of sPP, as indicated in the X-ray diffraction profiles by the presence of the 200, 020, and 220 + 121 reflections at 2θ ≈ 12, 16, and 21°, respectively (curve a of Figure 6).37c,39−41 The absence of the 211 reflection at 2θ = 18.8° in the diffraction profiles (curve a of Figure 6) indicates that the crystals of form I are characterized by a high degree of structural disorder consisting in the departures from the perfect alternation of right- and lefthanded helical chains along the axes of the orthorhombic unit cell of form I.39,40 We recall that form I of sPP is characterized by chains in the 2-fold helical conformation packed in an orthorhombic unit cell with axes a = 14.5 Å, b = 11.2 Å, and c = 7.4 Å, where helical chains with opposite chirality right-handed and left-handed, alternate along a and b axes of the unit cell,

macromonomer was observed by GPC and decreased conversion (93%) was revealed through analysis of the 1H NMR spectrum. Attempts to decrease catalyst loadings further did not result in higher molecular weight poly(macromonomer) instead a considerable decrease in percent conversion was observed. Comparison of the GPC chromatogram of exo-MM-3600 (Figure 5) and exo-MM-5600 (Figure

Figure 5. GPC trace of exo-MM-3600 (pink, entry 1, Table 1) and poly(MM-3600) produced using 3 with 50:1 (blue, entry 1, Table 4) and 200:1 (green, entry 2, Table 4) [MM]o:[Ru].

S11, Supporting Information) with the poly(macromonomer)s produced at 50:1 and 200:1 catalyst loadings shows a clear increase in molecular weight with decreased catalyst loading. In general, polymerization of exo-MM-3600 resulted in high conversion to poly(macromonomer) (>88%) with low molecular weight distributions (Mw/Mn = 1.21−1.31) observed for a range of molecular weights (Mn = 86 000−172 000 g/ mol). Decreased molecular weights (Mn = 45 000−120 000 g/ mol, Mw/Mn = 1.30−1.89) were observed for the polymerization of exo-MM-5600 due to an increased presence of unfunctionalized macromonomer compared with exo-MM3600. However, the polymerization proceeded with good conversion (>93%) resulting in a highly syndiotactic polypropylene comb polymer. The thermal properties (Table 4) of the syndiotactic macromonomers and the resultant comb-polymers were also investigated using differential scanning calorimetry. Decreased melting temperatures were observed for the poly(macromonomer)s (Tm = 104−106 °C) compared with exoMM-3600 (Tm = 112 °C). Similar to the exo-MM-3600 series, the poly(macromonomer)s (Tm = 135 °C) obtained from the polymerization of exo-MM-5600 (Tm = 145 °C) display lower melting temperatures than the corresponding macromonomer. The DSC curve of exo-MM-5600 reveals a double melting endotherm with the second peak (Tm = 145 °C) being more pronounced than the first (Figure S9, Supporting Information). Previous reports for syndiotactic polypropylene suggest that initial melting is followed by an immediate recrystallization resulting in the observed peaks.29b,37 Interestingly, the poly(macromonomer) obtained from exo-MM-5600 also displays a double endotherm, however, the initial peak (Tm = 135 7870


Macromolecules

Article

form I with a high amount of right/left substitution type disorder of helices in the lattice positions. This is indicated in curves b−d (Figure 6A) by the presence of the 200, 020, and 220 + 121 reflections at 2θ ≈ 12, 16, and 21°, respectively, and the absence of 211 reflection at 2θ = 18.8°, which is typical of modifications close to the limit disordered form I.39,40 However, at high crystallization temperatures, in the case of the macromonomer the degree of order of form I tends to increase with the temperature, as indicated by the gradual increase of intensity of the 211 reflection at 2θ = 18.8° in curves e, f (Figure 6A).39 In the case of the poly(macromonomer) ordered modifications of form I are not formed and small amounts of crystals of isochiral form II are observed along with a prevalent amount of crystals in disordered modification of antichiral form I. This is indicated in the X-ray diffraction profiles (curves e,f of Figure 6B) by the presence of 200, 020, and 220 + 121 reflections at 2θ ≈ 12, 16, and 21° respectively and the absence of 211 reflection at 2θ = 18.8°, which indicates disordered modifications of form I.39 In addition, a shoulder at 2θ = 17° is also present, which is typical of isochiral form II.41,43 It is worth noting that a small shoulder at 2θ = 17° is also present in the X-ray powder diffraction profiles of the macromonomer as indicated by the asterisk in curves a and c of Figure 6A. In the case of the macromonomer, this peak disappears with increasing crystallization temperature and ordered modifications of form I are obtained (curves d−f of Figure 6A). Alternatively, for the poly(macromonomer), the relative intensity of the peak at 2θ = 17° increases with Tc and the (211)I reflection may be considered practically absent (curves d−f of Figure 6B). We recall that form II of sPP is metastable and is characterized by chains in a 2-fold helical conformation packed in an orthorhombic unit cell with axes identical to those of form I but the b-axis halved, where isochiral chains are packed according to the space group C2221.43a The X-ray powder diffraction profiles of form II are similar to form I of sPP with 200 and 210 + 111 reflections at 2θ ≈ 12 and 21° respectively. The main difference between form II and form I is in the second strong diffraction peak located at 2θ ≈ 17°, corresponding to 110 reflection in the case of form II, and at 2θ ≈ 16°, corresponding to 020 reflection in the case of form I.41 Crystallization of isochiral form II from the melt in isothermal conditions at high temperatures is unusual, since normal crystallization conditions typically result in the more stable antichiral form I.37c However, X-ray powder

Figure 6. X-ray powder diffraction profiles recorded at room temperature of as-prepared (a) and melt crystallized specimens (b− f) obtained by isothermal crystallization at the indicated temperatures Tc of the macromonomer MM-3600-80 (A) and corresponding comblike poly(macromonomer) PM-3600-80 (B). The 200, 020, 211, and 220 + 121 reflections of form I and 200, 110, and 210 + 111 reflections of form II are indicated.

according to the space goup Ibca.40,41 A characteristic type of structural disorder frequently observed in melt and/or solution crystallized sPP samples consists in departures from the perfect alternation of right- and lefthanded helices along the a and b axes of the unit cell.40,41 The absence or the low intensity of 211 reflection at 2θ = 18.8° in the diffraction patterns of sPP samples is the hallmark of such a kind of disorder.39−41 In Figure 6, we also observe that the X-ray powder diffraction profiles of as-prepared samples (curves a) show the presence of a broad peak in the range 2θ = 13−19°, centered on the 020 reflection at 2θ = 16°. This indicates that a high amount of disorder in the stacking of bc layers of chains along a, implying shifts of bc layers of chains of b/4 along b, is also present.39,42 The degree of crystallinity is around 30% for both samples. Isothermal crystallization carried out at increasing temperatures produces a different effect on the crystal structure that develops from the melt for the macromonomer and the corresponding comb-poly(macromonomer) (curves b−f of Figure 6). In fact, at low crystallization temperatures, both samples crystallize in disordered modifications of antichiral

Figure 7. DSC thermograms recorded during the I heating (a), successive cooling (b) and II heating (c) scans of the macromonomer exo-MM-360080 (A) and the corresponding comb-like poly(macromonomer) PM-3600-80 (B) at scanning rate of 10 °C/min. The glass transition temperature Tg is indicated. 7871


Macromolecules

Article

Figure 8. DSC thermograms recorded during the isothermal crystallization at the indicated crystallization temperatures Tc (A, A′, C) and the successive heating scan from Tc to 200 °C (B, D) of the macromonomer exo-MM-3600-80 (A, A′, B) and the corresponding comb-like poly(macromonomer) PM-3600-80 (C, D). The values of crystallization enthalpy ΔHc∞ relative to the isothermal process (A, A′, C) and melting enthalpy recorded during the successive heating ΔHm(tmax) (B, D) are indicated.

in Figure 7. The DSC curves recorded during the first heating scan (curves a of Figure 7) show multiple melting endotherms spanning the region 40−135 °C. The main melting peak is located at ≈112 °C for the macromonomer exo-MM-3600-80 and at ≈102 °C for the corresponding poly(macromonomer) PM-3600-80 for a total meting enthalpy ΔHm of ≈47 and ≈44 J/g, in the two cases, respectively. The multiple endotherms for the macromonomer and the corresponding poly(macromonomer) merge into a double melting endotherm in the case of melt-crystallized samples (curves c of Figure 7). More precisely, the DSC data recorded during the cooling run (curves b of Figure 7) and the II heating scan (curves c of Figure 7) essentially confirm the results of thermal analysis discussed in the preceding session. In brief, the macromonmer exo-MM-3600-80 and the corresponding poly(macromonomer) PM-3600-80 show a single crystallization exotherm located at ≈65 and ≈50 °C, respectively, and two melting peaks in the successive heating scan located at ≈97 and 112 °C for the macromomer and 98 and 101 °C for the poly(macromonomer), with melting enthalpy ΔH of ≈31 and ≈27 J/g, respectively. Whereas the second melting peak is more pronounced than the first one in the case of the macromonomer, the peak at high temperature appears as shoulder of main peak at 97 °C in the case of poly(macromonomer). Therefore, the melting and crystallization temperatures decrease by 10−15 °C upon polymerization of the macromonomer and the values of melting enthalpy decrease only slightly. We also notice from DSC curves of Figure 7 that, upon polymerization, the glass transition temperature Tg of the macromonomer located at ≈−9 °C increases to ≈−4 °C in the case of the poly(macromonomer). This suggests that the

diffraction profiles similar to those of the polymacromonomer (curves e, f of Figure 6B) have also been obtained for sPP samples with low stereoregularity ([rrrr] = 70−80%) by isothermal crystallization from the melt at high and low temperatures.35,38 It has been argued that in these samples the presence of a broad 020 reflection at 2θ ≈ 16° of form I, with a shoulder or a small peak at 2θ ≈ 17°, corresponding to the 110 reflection of form II, and the low intensity, or the absence, of the 211 reflection at 2θ ≈ 18° indicates that either small amounts of crystals of form II are present and/or a mode of packing of form II occurs as a defect in a prevailing mode of packing as in form I, due to the occurrence of the b/4 shifts disorder.37c,39,42 The reasons why melt-crystallization above a critical temperature in isothermal conditions produces ordered modifications of form I in the case of the macromonomer MM3600-80 (curves e, f of Figure 6A), and a local packing mode of form II in the case of the corresponding polymacromonomer is not clear. A possible reason may be envisaged in the reduced mobility of the backbone chain of the comb-shaped polymacromonomer whose side chains experience crystallization in a more constrained environment than in the case of the macromonomer. The crystallization of sPP side chains in disordered modifications of form I containing a high amount of b/4 shift disorder or the partial crystallization into form II is probably driven by the high rigidity of the backbone of the comb polymer, due to the major ability of the isochiral form II withstanding compressive forces when compared with the antichiral form I.44 The DSC thermograms of as-prepared samples recorded during the first heating, successive crystallization step and second heating run at scanning rate of 10 °C/min are reported 7872


Macromolecules

Article

Figure 9. Apparent crystallinity xc′(t) as a function of the crystallization time of specimens of the macromonomer exo-MM-3600-80 (A) and the poly(macromonomer) PM-3600-80 (B) isothermally crystallized from the melt at the indicated crystallization temperatures Tc, corresponding halfcrystallization time t1/2 (C) and melting temperature Tm (D) as a function the crystallization temperature Tc for the macromonomer (●, ■) and poly(macromonomer) (○, □). Experimental values of the apparent crystallinity xc′(t) in A,B have been roughly fitted to Avrami expression (eq 1) using the following values of the parameters τ and n (solid lines): Tc = 80 °C, τ =200 s, n = 3.8; Tc = 90 °C, τ =653 s, n = 3.8; Tc = 100 °C, τ =2538 s, n = 3.8; Tc = 105 °C, τ =5681 s, n = 3.8 in A. Tc = 60 °C, τ =110 s, n = 3.8; Tc = 70 °C. τ =172 s, n = 3.8; Tc = 80 °C, τ =481 s, n = 2.5; Tc = 90 °C, τ =1828 s, n = 3.6; Tc = 100 °C, τ = 4938 s, n = 3.8 in B. Melting temperatures in D corresponding to peak 1 (●, ○) and peak 2 (■, □) are measured from the DSC curves of Figure 8B,D recorded at heating rate of 2.5 °C/min immediately after completion of crystallization at Tc. Extrapolations to the line Tm = Tc are indicated.

melting peak whose position is invariant with crystallization temperature is also present (peaks 3 of Figure 8B,D) for both samples at ≈132 °C. It is worth noting that the crystallization enthalpy involved during isothermal crystallization ΔHc∞ (Figure 8A,A′,C) is in all cases numerically coincident (in absolute value) with the melting enthalpy ΔHm(tmax) recorded during the successive heating scan (Figure 8B,D). This fact may be taken as an indication that eventual phenomena of melting/ recrystallization and/or perfectioning of crystals associated with secondary crystallization during the crystallization step or occurring during the heating at 2.5 °C/min in the successive heating scan are either small or conceal each other. The presence of double endothermic peaks (peaks 1 and 2 of Figure 8B,D) in poorly stereoregular sPP samples isothermally crystallized from the melt has been already described in the literature.29,43b They have been attributed to the occurrence of melting immediately followed by recrystallization,29,43b even though the presence of two populations of crystals characterized by different concentration and/or kinds of defects and different lamellar thickness formed simultaneously at the same Tc may not be excluded. The fact that melting starts immediately above the crystallization temperature (starred peaks of Figure 8B,D) instead, has been attributed to the presence of not yet well formed crystals during the isothermal crystallization step.29b Finally, the presence of a small melting peak at 132 °C whose position does not depend on the crystallization temperature is a peculiarity of the systems under study. It may be due to formation during the heating scan at 2.5

crystallization ability of sPP moieties in the comb polymer is only slightly affected by the rigid constraints of chain backbone and only the melting and crystallization temperatures are affected. We hypothesize that the differences in the melting and crystallization temperature of the macromonomer and the corresponding poly(macromonomer) are related to a decrease in mobility of the side chains in the comb polymer (associated with the increase of the glass transition temperature) which somehow influences the crystallization kinetics of sPP. The crystallization kinetics of the macromonomer and the corresponding poly(macromonomer) were investigated by performing DSC measurements. The DSC thermograms were recorded during isothermal crystallization at different crystallization temperatures (Tc) for at least 4 h or until complete crystallization at that Tc was achieved. The DSC curves recorded during the successive heating from Tc to 200 °C are shown in Figure 8. The crystallization isotherms have the classical bell-shaped form (Figure 8A,A′,C). After an induction time that increases with the crystallization temperature Tc, both samples show a single peaked crystallizaton exotherm whose area decreases with Tc. The DSC curves recorded during the successive heating (Figure 8B,D) show multiple endotherms indicating that melting starts immediately above the crystallization temperature (starred peaks of Figure 8B,D). For both samples, two main melting peaks (peaks 1 and 2 in Figure 8B,D) are present at temperatures that increase with Tc. In the case of the polymacromonomer at Tc = 80 and 90 °C, peak 2 is buried by the broad peak 1 at lower temperature. A third faint 7873


Macromolecules

Article

°C/min of more perfect and thick crystals in the case of the macromonomer and/or in the case of the poly(macromonomer), to the eventual presence of small amounts of unreacted macromonomer. We also notice that the crystallization enthalpy ΔHc∞ (Figure 8A,A′,C) decreases with increasing the crystallization temperature indicating that the maximum degree of crystallinity achieved by isothermal crystallization at any Tc also decreases. More precisely, in the case of the macromonomer the degree of crystallinity decreases from the value of ≈13% (= 2400/190)29 at Tc = 80 °C to ≈8% (=1600/190)29 at Tc = 100 °C down to ≈6% (=900/190)29 at Tc = 105 °C, whereas in the case of the poly(macromonomer) decreases from the value of ≈13% (=2500/190)29 at Tc = 60− 70 °C to ≈11% (2200/190)29 at Tc = 80 °C down to ≈5% (=1000/190)29 at Tc = 100 °C. These data also suggest that at any given Tc the crystallization ability of sPP side chains in the comb polymer decreases only slightly in isothermal crystallizations with respect to that one of the macromonomer. At present, we have not investigated in detail the origin of the multiple endothermic peaks arising from isothermal crystallization of our samples (Figure 8B,D), further investigation to explain this behavior is currently underway. The data of Figure 8 have instead been used to find the parameters of crystallization kinetics to explain the main differences in the crystallization behavior of the macromonomer exo-MM-360080 and the corresponding poly(macromonomer) PM-3600-80. In particular, the DSC data recorded during the isothermal crystallization at various Tc as a function of crystallization time of Figure 8A,A′,C have been used to evaluate the apparent degree of cystallinity x′c(t), obtaining the classical sigmoidal curves shown in Figure 9A,B. Experimental data could be roughly fitted to the conventional Avrami equation: ⎧ ⎡ ⎛ t ⎞ n ⎤⎫ x′c (t ) = 100⎨1 − exp⎢ −⎜ ⎟ ⎥⎬ ⎣ ⎝ τ ⎠ ⎦⎭ ⎩

at different Tc, which can be obtained from the maxima of the endothermic peaks in the DSC heating curves recorded from Tc immediately after the completion of isothermal crystallizations without cooling to room temperature, shown in Figure 8B,D. Because of the lack of more precise information on the origin of peak 1 and peak 2 in the DSC thermograms of Figure 8B,D, both the temperatures have been used in the Hoffmann-Weeks extraplation procedure of Figure 9D. Surprisingly, in spite of the different kind of polymorphism shown by the macromonomer and the corresponding comb polymer in isothermal crystallization (Figure 6), the melting temperatures of the two samples could be fitted to a unic straight line, obtaining a unic value of Tm0 for the two samples, equal to Tm0 = 119 °C from extrapolation of peak 1 and 129 °C from extrapolation of peak 2. The value of Tm0 of 129 °C is in a better agreement with the presence in the DSC thermograms of our isothermally crystallized samples (Figure 8B,D) of peak 3 at ≈132 °C whose position is invariant with the crystallization temperature for both samples. On the other hand, the linear extrapolation of melting temperatures relative to peak 1 and peak 2 to different values of Tm0 along with the use of straight lines with identical slope is also surprising, and although suggesting the idea that the double melting behavior of our samples originate from the presence of different populations of crystallites, occurrence of melting recrystallization phenomena due to the formation of imperfect crystals at any Tc may not be ruled out.46 The correctness in the use of the Hoffman−Weeks method45 for finding the values of equilibrium melting temperature has aroused some skepticism in the literature.46 For instance, according to Stobl,46b this temperature does not represent the Tm0 value but just gives an estimate of the temperature where the crystal growth rate has become low enough to avoid all kinetic effects, so that perfect crystals are formed immediately and are not subjected to melting recrystallization phenomena. Whatever the meaning of the Tm0 value found in the Hoffman− Weeks extrapolation procedure, the unic value of Tm0 for the macromonomer and the corresponding comb polymer of Figure 9D suggest that it is reasonable to compare the kinetic data of the macromonomer exo-MM-3600-80 and the poly(macromonomer) PM-3600-80 obtained by isothermal crystallization of Figure 9C at the same Tc. This data indicates that the principal effect of macromonomer polymerization results in a slowing down by a factor equal to 2−3 the crystallization kinetics of the sPP chains, probably due to the constrains imposed by the rigid backbone of the comb polymer. The low crystallization kinetics of sPP chains in the comb polymer make it possible to elucidate the differences observed in the melting and crystallization behavior of our samples under nonisothermal conditions. Specifically, DSC thermograms of Figures 7, S7, and S8, Supporting Information, revealed the remarkable decrease of 15−20 °C in the crystallization temperature and the decrease by ≈10 °C in melting temperature of the poly(macromonomer) with respect to the crystallization and melting temperatures of the corresponding macromonomer. The depression of crystallization temperature of the poly(macromonomer) in the DSC scan, indeed, imply a lower crystallization kinetics as compared with the corresponding macromonomer.

(1)

We have found that the characteristic time (τ) increases with crystallization temperature (Tc) in both samples. The exponent n is instead essentially constant with the crystallization temperature and equal to ≈3.8 in the case of macromonomer (Figure 9A), whereas, in the case of the poly(macromonomer), is ≈3.8 at Tc =60 and 70 °C, decreases to ≈2.5 at Tc = 80 °C and increases again to ≈3.6 and 3.8 at Tc =100 and 105 °C, respectively. The change in the Avrami exponent observed in the temperature range Tc = 80−90 °C is probably associated with a crossover in the crystallization regime in the case of the comb polymer. The values of the half-crystallization time t1/2 (time at which half of the crystallizable materials is crystallized) are reported in Figure 9C as a function of the crystallization temperature. It is apparent that at any Tc the crystallization rate of the macromonomer is 2−3 times higher than that of the corresponding poly(macromonomer). However direct comparison of crystallization half time should be performed at identical values of undercooling (ΔT = Tm0 - Tc with Tm0 the equilibrium melting temperatures of the macromonomer exoMM-3600-80 and the poly(macromonomer) PM-3600-80). The values of Tm0 have been determined by application of the Hoffman−Weeks standard method.45 According to this method, the values of melting temperatures (Tm) are plotted against Tc and the point where Tm equals Tc is taken as the equilibrium melting point (Figure 9D).45 We have used the melting temperatures of the samples crystallized from the melt

■

CONCLUSIONS Ring-opening metathesis polymerization of norbornene-terminated syndiotactic polypropylene resulted in high molecular weight poly(macromonomer)s. To the best of our knowledge, 7874


Macromolecules

Article

this is the first report of a comb polymer from endfunctionalized syndiotactic polypropylene. Utilizing allylterminated syndiotactic polypropylene obtained from bis(phenoxyimine)titanium catalysts, 1 and 2, hydroxyl- and norbornene-terminated polymers of varying tacticity were obtained. The macromonomer, exo-MM-3600, was polymerized with ruthenium catalysts 3−5 to produce the poly(macromonomer)s. Reaction rate was investigated with catalyst 3 and initially the polymerization proceeded quickly, though longer reaction times were required to obtain high conversions. Poly(macromonomer)s with a range of molecular weights were obtained from exo-MM-3600 and exo-MM-5600 by varying catalyst loadings. The resultant comb polymers displayed interesting thermal properties with both melting temperature and crystallization temperature decreasing upon formation of the high molecular weight poly(macromonomer). Preliminary results relative to the crystallization kinetics under isothermal conditions indicate that the possible origin of the decrease of melting and crystallization temperatures of norborne-terminated syndiotactic polypropylene macromonomers upon formation of the high molecular mass poly(macromonomer) are due to the crystallization kinetics of the sPP chains slowing down by a factor of approximately 2−3, which is probably due to the constrains imposed by the rigid back of the comb polymer.

■

(2) Vasile, C. In Handbook of Polyolefins, 2nd ed.; Vasile, C., Ed.; Marcel Dekker Inc: New York, 2000; pp 401−412. (3) (a) Chum, S.; Swogger, K. W. Prog. Polym. Sci. 2008, 33, 797− 819. (b) Rojas, G.; Berda, E. B.; Wagener, K. B. Polymer 2008, 49, 2985−2995. (c) Gahleitner, M. Prog. Polym. Sci. 2001, 26, 895−944. (d) Doerpinghaus, P. J.; Baird, D. G. J. Rheol. 2003, 47, 717−736. (4) Lagendijk, R. P.; Hogt, A. H.; Buijtenhuijs, A.; Gotsis, A. D. Polymer 2001, 42, 10035−10043. (5) (a) Gahleitner, M. Prog. Polym. Sci. 2001, 26, 895−944. (b) Lohse, D. J.; Milner, S. T.; Fetters, L. J.; Xenidou, M.; Hadjichristidis, N.; Mendelson, R. A.; Garcia-Franco, C. A.; Lyon, M. K. Macromolecules 2002, 35, 3066−3075. (c) Li, S.; Xiao, M.; Guan, Y.; Wei, D.; Xiao, H.; Zheng., A. Eur. Polym. J. 2012, 48, 362−371. (d) McCallum, T. J.; Kontopoulou, M.; Park, C. B.; Muliawan, E. B.; Hatzikiriakos, S. G. Poly. Eng. Sci. 2007, 47, 1133−1140. (6) (a) Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iatrou, H. Chem. Rev. 2001, 101, 3747−3792. (b) Sheiko, S. S.; Möller, M. Chem. Rev. 2001, 101, 4099−4123. (c) Zhang, M.; Müller, A. H. E. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 3461−3481. (d) Voit, B. I.; Lederer, A. Chem. Rev. 2009, 109, 5924−5973. (e) Peleshanko, S.; Tsukruk, V. V. Prog. Polym. Sci. 2008, 33, 523−580. (f) Ito, Koichi Prog. Polym. Sci. 1998, 23, 581−620. (g) Sheiko, S. S.; Sumerlin, B. S.; Matyjaszewski, K. Prog. Polym. Sci. 2008, 33, 759−785. (h) Ito, K.; Kawaguchi, S. Adv. Polym. Sci. 1999, 142, 129−178. (7) (a) Runge, M. B.; Dutta, S.; Bowden, N. B. Macromolecules 2006, 39, 498−508. (b) Xia, Y.; Olsen, B. D.; Kornfield, J. A.; Grubbs, R. H. J. Am. Chem. Soc. 2009, 131, 18525−18532. (c) Xia, Y.; Kornfield, J. A.; Grubbs, R. H. Macromolecules 2009, 42, 3761−3766. (8) Huang, K.; Rzayev, J. J. Am. Chem. Soc. 2009, 131, 6880−6885. (9) Sarkar, D.; El Khoury, J. M.; Lopina, S. T.; Hu, J. J. Appl. Polym. Sci. 2007, 104, 1905−1911. (10) Yuan, J.; Lu, Y.; Schacher, F.; Lunkenbein, T.; Weiss, S.; Schmalz, H.; Müller, A. H. E. Chem. Mater. 2009, 21, 4146−4154. (11) (a) Gao, H.; Matyjaszewski, K. J. Am. Chem. Soc. 2007, 129, 6633−6639. (b) Bousquet, A.; Barner-Kowollik, C.; Stenzel, M. H. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 1773−1781. (c) Bao, H.; Hu, J.; Gan, L. H.; Li, L. J. Polym. Sci., Part A: Poly. Chem. 2009, 47, 6682−6692. (12) (a) Runge, M. B.; Bowden, N. B. J. Am. Chem. Soc. 2007, 129, 10551−10560. (b) Jha, S.; Dutta, S.; Bowden, N. B. Macromolecules 2004, 37, 4365−4374. (c) Runge, M. B.; Yoo, J.; Bowden, N. B. Macromol. Rapid Commun. 2009, 30, 1392−1398. (13) Zhang, N.; Steenackers, M.; Luxenhofer, R.; Jordan, R. Macromolecules 2009, 42, 5345−5351. (14) Cheng, X.; Ma, J.; Zhi, J.; Yang, X.; Hu, A. Macromolecules 2010, 43, 909−913. (15) (a) Runge, M. B.; Lipscomb, C. E.; Ditzler, L. R.; Mahanthappa, M. K.; Tivanski, A. V.; Bowden, N. B. Macromolecules 2008, 41, 7687− 7694. (b) Yoo, J.; Runge, B.; Bowden, N. B. Polymer 2011, 52, 2499− 2504. (c) Matson, J. B.; Grubbs, R. H. J. Am. Chem. Soc. 2008, 130, 6731−6733. (d) Johnson, J. A.; Lu, Y. Y.; Burts, A. O.; Xia, Y.; Durrell, A. C.; Tirrell, D. A.; Grubbs, R. H. Macromolecules 2010, 43, 10326− 10335. (e) Johnson, J. A.; Lu, Y. Y.; Burts, A. O.; Lim, Y.-H.; Finn, M. G.; Koberstein, J. T.; Turro, N. J.; Tirrell, D. A.; Grubbs, R. H. J. Am. Chem. Soc. 2011, 133, 559−566. (f) Montembault, D. L.; Soutif, J.-C.; Rutnakornpituk, M.; Fontaine, L. Macromolecules 2010, 43, 5611− 5617. (g) Li, Z.; Zhang, K.; Ma, J.; Cheng, C.; Wooley, K. L. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 5557−5563. (h) Li, Z.; Ma, J.; Cheng, C.; Zhang, K.; Wooley, K. L. Macromolecules 2010, 43, 1182− 1184. (i) Li, Z.; Ma, J.; Lee, N. S.; Wooley, K. L. J. Am. Chem. Soc. 2011, 133, 1228−1231. (16) Zhao, L.; Goodman, M. D.; Bowden, N. B.; Lin, Z. Soft Matter 2009, 5, 4698−4703. (17) Rose, J. M.; Mourey, T. H.; Slater, L. A.; Keresztes, I.; Fetters, L. J.; Coates, G. W. Macromolecules 2008, 41, 559−567. (18) (a) Kaneko, H.; Kojoh, S.-I.; Kawahara, N.; Matsuo, S.; Matsugi, T.; Kashiwa, N. J. Polym. Sci., Part A: Polym. Chem. 2005, 43, 5103− 5118. (b) Kaneko, H.; Kojoh, S.; Kawahara, N.; Matsuo, S.; Matsugi, T.; Kashiwa, N. Macromol. Symp. 2004, 213, 335−345.

ASSOCIATED CONTENT

S Supporting Information *

Full 1H NMR spectra for end-functionalized polypropylene and poly(exo-MM-3600), 13C NMR spectra of polypropylene produced with 1 and 2, GPC chromatograms for exo-MM5600 and poly(exo-MM-5600), DSC thermograms of exo-MM3600, poly(exo-MM-3600), exo-MM-5600 and poly(exo-MM5600), characterization data for exo-MM-3600-80 and poly(exoMM-3600-80), and the scaled up procedure for synthesizing poly(exo-MM-3600-80). This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS G.W.C. gratefully acknowledges support from National Science Foundation (DMR-0706578). This research made use of the Cornell Center for Materials Research Shared Experimental Facility supported through the NSF MRSEC program (DMR0520404).

■

REFERENCES

(1) (a) Coates, G. W. Chem. Rev. 2000, 100, 1223−1252. (b) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem. Rev. 2000, 100, 1253− 1345. (c) Domski, G. J.; Rose, J. M.; Coates, G. W.; Bolig, A. D.; Brookhart, M. Prog. Polym. Sci. 2007, 32, 30−92. (d) Lopez, R. G.; D’ Agosto, F.; Boisson, C. Prog. Polym. Sci. 2007, 32, 419−454. (e) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143− 1170. (f) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283− 315. (g) Matsugi, T.; Fujita, T. Chem. Soc. Rev. 2008, 37, 1264−1277. (h) Delferro, M.; Marks, T. J. Chem. Rev. 2011, 111, 2450−2485. 7875


Macromolecules

Article

(19) (a) Doi, Y.; Hizal, G.; Soga, K. Makromol. Chem. 1987, 188, 1273−1279. (b) Doi, Y.; Keii, T. Adv. Polym. Sci. 1986, 73/74, 201. (c) Doi, Y.; Murata, M.; Soga, K. Makromol. Chem. Rapid Commun. 1984, 5, 811−814. (d) Doi, Y.; Tokuhiro, N.; Suzuki, S.; Soga, K. Makromol. Chem. Rapid Commun. 1987, 8, 285−290. (e) Doi, Y.; Watanabe, Y.; Ueki, S.; Soga, K. Makromol. Chem. Rapid Commun. 1983, 4, 533−537. (f) Gottfried, A. C.; Brookhart, M. Macromolecules 2003, 36, 3085−3100. (g) Ueki, S.; Furuhashi, H.; Murakami, N.; Murata, M.; Doi, Y. Sci. Technol. Catal. 1995, 92, 359−362. (h) Makio, H.; Fujita, T. Macromol. Rapid Commun. 2007, 28, 698−703. (20) (a) Kuo, J.-C.; Lin, W.-F.; Yu, C.-H.; Tsai, J.-C.; Wang, T.-C.; Chung, T.-M.; Ho, R.-M. Macromolecules 2008, 41, 7967−7977. (b) Lin, W.-F.; Tsai, J.-C. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 2167−2176. (c) Lin, W.-F.; Hsiao, T.-J.; Tsai, J.-C.; Chung, T. M.; Ho, R.-M. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 4843−4856. (d) Reddy, K. R.; Kumar, B.; Rana, S.; Tevtia, A. K.; Singh, R. P. J. Appl. Polym. Sci. 2007, 104, 1596−1602. (e) Lehmus, P.; Kokko, E.; Leino, R.; Luttikhedde, H. J. G.; Rieger, B.; Seppälä, J. V. Macromolecules 2000, 33, 8534−8540. (f) Kojoh, S.; Tsutsui, T.; Kiola, M.; Kashiwa, N. Polym. J. 1999, 31, 332−335. (g) Koo, K.; Marks, T. J. J. Am. Chem. Soc. 1999, 121, 8791−8802. (h) Kaneyoshi, H.; Matyjaszewski, K. J. Appl. Polym. Sci. 2007, 105, 3−13. (i) Shiono, T.; Kurosawa, H.; Ishida, O.; Soga, K. Macromolecules 1993, 26, 2085− 2089. (j) Shiono, T.; Soga, K. Macromolecules 1992, 25, 3356−3361. (k) Kaneko, H.; Matsugi, T.; Kawahara, N.; Matsuo, S.; Kojoh, S.; Kashiwa, N. Kinet. Catal. 2006, 47, 227−233. (l) Weng, W.; Markel, E. J.; Dekmezian, A. H. Macromol. Rapid Commun. 2000, 21, 1103−1107. (m) Kawahara, N.; Kojoh, S.; Matsuo, S.; Kaneko, H.; Matsugi, T.; Toda, Y.; Mizuno, A.; Kashiwa, N. Polymer 2004, 45, 2883−2888. (21) (a) Shiono, T.; Hiroki, K.; Soga, K. Macromolecules 1994, 27, 2635−2637. (b) Chung, T. C.; Xu, G.; Lu, Y.; Hu, Y. Macromolecules 2001, 34, 8040−8050. (c) Kaneyoshi, H.; Inoue, Y.; Matyjaszewski, K. Macromolecules 2005, 38, 5425−5435. (d) Hagihara, H.; Ishihara, T.; Ban, H. T.; Shiono, T. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 1738−1747. (e) Lin, W.; Dong, J.; Chung, T. C. M. Macromolecules 2008, 41, 8452−8457. (f) Yi, Q.; Fan, G.; Wen, X.; Dong, J.-Y.; Han, C. C. Macromol. React. Eng. 2009, 3, 91−100. (g) Briquel, R.; Mazzolini, J.; Le Bris, T.; Boyron, O.; Boisson, F.; Delolme, F.; D’ Agosto, F.; Boisson, C.; Spitz, R. Angew. Chem., Int. Ed. 2008, 47, 9311−9313. (22) (a) Mowery, D. M.; Assink, R. A.; Derzon, D. K.; Klamo, S. B.; Clough, R. L.; Bernstein, R. Macromolecules 2005, 38, 5035−5046. (b) Hagiwara, T.; Saitoh, H.; Tobe, A.; Sasaki, D.; Yano, S.; Sawaguchi, T. Macromolecules 2005, 38, 10373−10378. (23) (a) Resconi, L.; Camurati, I.; Sudmeijer, O. Top. Catal. 1999, 7, 145−163. (b) Lahelin, M.; Kokko, E.; Lehmus, P.; Pitkänen, P.; Löfgren, B.; Seppälä, J. Macromol. Chem. Phys. 2003, 204, 1323−1337. (c) Resconi, L.; Jones, R. L.; Rheingold, A. L.; Yap, G. P. A. Organometallics 1996, 15, 998−1005. (24) Cherian, A. E.; Lobkovsky, E. B.; Coates, G. W. Macromolecules 2005, 38, 6259−6268. (25) (a) Ye, Z.; Zhu, S. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 1152−1159. (b) Britovsek, G. J. P.; Gibson, V. C.; Kimberley, B. S.; Maddox, P. J.; McTavish, S. J.; Solan, G. A.; White, A. J. P.; Williams, D. J. Chem. Commun. 1998, 849−850. (c) Pellecchia, C.; Mazzeo, M.; Pappalardo, D. Macromol. Rapid Commun. 1998, 19, 651−655. (d) Small, B. L.; Brookhart, M. Macromolecules 1999, 32, 2120−2130. (26) (a) Iha, R. K.; Wooley, K. L.; Nyström, A. M.; Burke, D. J.; Kade, M. J.; Hawker, C. J. Chem. Rev. 2009, 109, 5620−5686. (b) Petzetakis, N.; Pitsikalis, M.; Hadjichristidis, N. J. Polym. Sci., Part A: Polym. Chem 2010, 48, 1092−1103. (c) Inglis, A. J.; Paulöhrl, T.; Barner-Kowollik, C. Macromolecules 2010, 43, 33−36. (d) Bellas, V.; Rehahn, M. Macromol. Chem. Phys. 2009, 210, 320−330. (e) Li, M.; De, P.; Gondi, S. R.; Sumerlin, B. S. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 5093−5100. (27) (a) Dag, A.; Durmaz, H.; Sirkecioglu, O.; Hizal, G.; Tunca, U. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 2344−2351. (b) Ohno, S.; Gao, H.; Cusick, B.; Kowalewski, T.; Matyjaszewski, K. Macromol. Chem. Phys. 2009, 210, 421−430. (c) Dag, A.; Durmaz, H.; Tunca, U.;

Hizal, G. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 178−187. (d) Gao, H.; Matyjaszewski, K. J. Am. Chem. Soc. 2007, 129, 11828− 11834. (e) Urbani, C. N.; Bell, C. A.; Lonsdale, D. E.; Whittaker, M. R.; Monteiro, M. J. Macromolecules 2007, 40, 7056−7059. (f) Hirao, A.; Hayashi, M.; Loykulnant, S.; Sugiyama, K.; Ryu, S. W.; Haraguchi, N.; Matsuo, A.; Higashihara, T. Prog. Polym. Sci. 2005, 30, 111−182. (g) Hirao, A.; Tokuda, Y. Macromolecules 2003, 36, 6081−6086. (h) Lammens, M.; Fournier, D.; Fijten, M. W. M.; Hoogenboom, R.; Prez, F. D. Macromol. Rapid Commun. 2009, 30, 2049−2055. (28) (a) Hustad, P. D.; Tian, J.; Coates, G. W. J. Am. Chem. Soc. 2002, 124, 3614−3621. (b) Makio, H.; Kashiwa, N.; Fujita, T. Adv. Synth. Catal 2002, 344, 477−493. (c) Mitani, M.; Saito, J.; Ishii, S.; Nakayama, Y.; Makio, H.; Matsukawa, N.; Matsui, S.; Mohri, J.; Furuyama, R.; Terao, H.; Bando, H.; Tanaka, H.; Fujita, T. Chem. Rec. 2004, 4, 137−158. (d) Tian, J.; Coates, G. W. Angew. Chem., Int. Ed. 2000, 39, 3626−3629. (e) Milano, G.; Fiorello, G.; Guerra, G.; Cavallo, L. Macromol. Chem. Phys. 2002, 203, 1564−1572. (f) Lamberti, M.; Gliubizzi, R.; Mazzeo, M.; Tedesco, C.; Pellecchia, C. Macromolecules 2004, 37, 276−282. (g) Talarico, G.; Busico, V.; Cavallo, L. J. Am. Chem. Soc. 2003, 125, 7172−7173. (h) Saito, J.; Mitani, M.; Onda, M.; Mohri, J.; Ishi, J. I.; Yoshida, Y.; Nakano, T.; Tanaka, H.; Matsugi, T.; Kojoh, S. I.; Kashiwa, N.; Fujita, T. Macromol. Rapid Commun. 2001, 22, 1072−1075. (i) Tian, J.; Hustad, P. D.; Coates, G. W. J. Am. Chem. Soc. 2001, 123, 5134−5135. (j) Mason, A. F.; Tian, J.; Hustad, P. D.; Lobkovsky, E. B.; Coates, G. W. Isr. J. Chem. 2002, 42, 301−306. (k) Mitani, M.; Mohri, J.; Yoshida, Y.; Saito, J.; Tsuru, K.; Matsui, S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.; Matsugi, T.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 3327−3336. (l) Mitani, M.; Furuyama, R.; Mohri, J.; Saito, J.; Ishii, S.; Terao, H.; Nakano, T.; Tanaka, H.; Fujita, T. J. Am. Chem. Soc. 2003, 125, 4293−4305. (m) Talarico, G.; Busico, V.; Cavallo, L. Organometallics 2004, 23, 5989−5993. (n) Mitani, M.; Nakano, T.; Fujita, T. Chem.Eur. J. 2003, 9, 2396−2403. (o) Lamberti, M.; Pappalardo, D.; Zambelli, A.; Pellecchia, C. Macromolecules 2002, 35, 658−663. (p) Mason, A. F.; Coates, G. W. J. Am. Chem. Soc. 2004, 126, 10798− 10799. (q) Makio, H.; Terao, H.; Iwashita, A.; Fujita, T. Chem. Rev. 2011, 111, 2363−2449. (29) (a) Rodriguez-Arnold, J.; Zhang, A.; Cheng, S. Z. D.; Lovinger, A. J.; Hsieh, E. T.; Chu, P.; Johnson, T. W.; Honnell, K. G.; Geerts, R. G.; Palackal, S. J.; Hawley, G. R.; Welch, M. B. Polymer 1994, 35, 1884−1895. (b) Schmidtke, J.; Strobl, G.; Thurn-Albrecht, T. Macromolecules 1997, 30, 5804−5821. (c) Haftka, S.; Könnecke, K. J. Macromol. Sci. Phys. 1991, B30, 319−334. (30) Miller, R. L.; Seeley, E. G. J. Polym. Sci., Polym. Phys. Ed. 1982, 20, 2297−2307. (31) Supaphol, P. J. Appl. Polym. Sci. 2001, 79, 1603−1609. (32) (a) Stammen, B.; Berlage, U.; Kindermann, R.; Kaiser, M.; Günther, B.; Scheldrick, W. S.; Welzel, P.; Roth, W. R. J. Org. Chem. 1992, 57, 6566−6575. (b) Liaw, D.-J.; Huang, C.-C.; Fu, C.-W. J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 4428−4434. (33) (a) Schaefgen, J. R.; Flory, P. J. J. Am. Chem. Soc. 1948, 70, 2709−2718. (b) Roovers, J. In Encylopedia of Polymer Science and Engineering, 2nd ed.; Mark, H. F., Bikales, N. M., Overberger, C. C., Menges, G., Kroschwitz, J. I., Eds.; Wiley-Interscience: New York, 1985−1990; Vol. 2, pp 478−499. (c) Schulz, G. V. Z. Phys. Chem. 1939, B43, 25. (34) Ulman, M.; Grubbs, R. H. J. Org. Chem. 1999, 64, 7202−7207. (35) (a) Bielawski, C. W.; Benitez, D.; Morita, T.; Grubbs, R. H. Macromolecules 2001, 34, 8610−8618. (b) Keitz, B. K.; Fedorov, A.; Grubbs, R. H. J. Am. Chem. Soc. 2012, 134, 2040−2043. (36) Lee, C. W.; Grubbs, R. H. Org. Lett. 2000, 2, 2145−2147. (37) (a) Ruokolainen, J.; Mezzenga, R.; Fredrickson, G. H.; Kramer, E. J.; Hustad, P. D.; Coates, G. W. Macromolecules 2005, 38, 851−860. (b) Supaphol, P.; Spruiell, J. E. J. Appl. Polym. Sci. 2000, 75, 44−59. (c) De Rosa, C.; Auriemma, F. Prog. Polym. Sci. 2006, 31, 145−237. (d) De Rosa, C.; Auriemma, F.; Vinti, V.; Galimberti, M. Macromolecules 1998, 31, 6206−6210. (e) De Rosa, C.; Circelli, T.; Auriemma, F.; Mathers, R. T.; Coates, G. W. Macromolecules 2004, 37, 9034−9047. 7876


Macromolecules

Article

(38) Hadjichristidis, N.; Pitsikalis, M.; Iatrou, H.; Pispas, S. Macromol. Rapid Commun. 2003, 24, 979−1013. (39) De Rosa, C.; Auriemma, F.; Vinti, V. Macromolecules 1997, 30, 4137−4146. (40) Lotz, B.; Lovinger, A. J.; Cais, R. E. Macromolecules 1988, 21, 2375−2382. (41) De Rosa, C.; Corradini, P. Macromolecules 1993, 26, 5711− 5718. (42) Lovinger, A. J.; Lotz, B.; Davis, D. D.; Padden, F. J. Macromolecules 1993, 26, 3494−3503. (43) (a) Corradini, P.; Natta., G.; Ganis, P.; Temussi, P. A. J. Polym. Sci., Part C 1967, 16, 2477−2484. (b) De Rosa, C.; Auriemma, F.; Vinti, V. Macromolecules 1998, 31, 7430−7435. (44) Rastogi, S.; La Camera, D.; van der Burgt, F.; Terry, A. E.; Cheng, S. Z. D. Macromolecules 2001, 34, 7730−7736. (45) Hoffman, J. D.; Weeks, J. J. J. Res. Natl. Bur. Stand. U.S.A. 1962, 66A, 13−28. (46) See, for instance: (a) Wunderlich, B. Macrmolecular Physics; Academic Press: New York, 1976; Vol. 2, Chapter 5.3 (b) Strobl, G. Prog. Polym. Sci. 2006, 31, 398−442.

7877


Synthesis and Ring-Opening Metathesis Polymerization of

Recommend Documents