Multiblock Thermoplastic Elastomers Derived from Biodiesel, Poly

Research Article pubs.acs.org/journal/ascecg

Multiblock Thermoplastic Elastomers Derived from Biodiesel, Poly(propylene glycol), and L‑Lactide Sangjun Lee,‡ Jeong Suk Yuk,‡ Hyejin Park,‡,§ Young-Wun Kim,*,‡,† and Jihoon Shin*,‡,† ‡

Center for Greenhouse Gas Resources, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Korea † Department of Advanced Materials & Chemical Engineering, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Korea § Department of Chemical Engineering, Inha University, 100 Inharo, Nam-gu, Incheon 22212, Korea S Supporting Information *

ABSTRACT: A series of [poly(L-lactide)−poly(dimer acid methyl ester-alt-poly(propylene glycol))−poly(L-lactide)]n (PLLA−PDP−PLLA)n multiblock copolymers was synthesized in a three-step procedure: PLLA−PDP−PLLA (LDPL) triblock copolymers were synthesized using ring-opening polymerization of L-lactide with PDP macroinitiators, which was prepared via step-growth melt polycondensation based on biodiesel and macro-diol, followed by chain extension of the LDPL triblock with 4,4′-methylenebis(phenyl isocyanate). Molecular characterization revealed that the synthetic procedures yielded the desired triblock and multiblock copolymers (f PLLA = 0.22−0.27). The relationship between thermal behavior and morphology indicated microphase separation into two domains in both the triblocks and multiblocks. Compared to previously reported triblocks with a high molar mass and PLLA hard blocks with inaccessible order−disorder transition temperature (TODT) values, the multiblock architectures in this study were found to become disordered at much lower temperatures (TODT = 82−128 °C). To prepare (LDPL)n multiblocks, coupling low-molar-mass LDPL triblocks without free-standing thin films led to dramatically enhanced tensile properties. The self-adhesive performance of the pressure-sensitive adhesive (PSA) system including the multiblocks was evaluated, showing a peel strength of 3.1 N cm−1, a probe tack of 1.9 N, and static shear strength of >50 000 min, which are values comparable to those of current PSAs. These biodiesel-based thermoplastic elastomers hold promise for sustainability and high value-added economy. KEYWORDS: Biodiesel, Melt polycondensation, Thermoplastic poly(ester-urethane) elastomers, Multiblock copolymers, Pressure-sensitive adhesives

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INTRODUCTION

been recently developed, in which a catalyst based on palladium and a special ligand, bis(di-tert-arybutylphosphinomethyl)benzene, can methoxycarbonylate methyl oleate to the linear α,ω-diester, dimethyl-1,19-nonadecanedioate (>95%).8,9 Polycondensation of stoichiometric amounts of the telechelic diester and nonadecane-1,19-diol afforded a novel semicrystalline long-chain poly(ester) with physical properties analogous to those of the ubiquitous thermoplastic low-density poly(ethylene) (LDPE).10 New ways to make biodiesel fuel production more economically attractive are needed. One alternative could be utilization of animal and vegetable fatty wastes for the production of biodiesel; however, multiple CC double

A mixture of fatty acid methyl esters (FAMEs) is commonly referred to as biodiesel, which is a renewable, nontoxic, and biodegradable fuel (Figure 1).1−5 However, in addition to burning, they can be used to make higher added-value materials for commodities and specialties, such as polyethylene, which can be obtained directly from plants without fermentation.6 To make poly(ester), in which long hydrocarbon chains are linked by ester linkages, the monomer must have an ester linkage at each end of a long chain. Poels et al. reported that pure methyl oleate was converted to dimethyl-1,18-octadecanedioate via self-metathesis and subsequent hydrogenation to make condensation polymers.7 The disadvantage of the functionalized alkene metathesis in oleochemical feedstocks is that only half of the naturally occurring molecule can be used, because of the formation of an internal alkene and an α,ω-diester with a double bond in the middle. An alternative methodology has © 2017 American Chemical Society

Received: June 5, 2017 Revised: July 7, 2017 Published: August 15, 2017 8148

DOI: 10.1021/acssuschemeng.7b01801 ACS Sustainable Chem. Eng. 2017, 5, 8148−8160

Research Article

ACS Sustainable Chemistry & Engineering

Figure 1. Chemical structures of building blocks derived from vegetable oil29 for the synthesis of polymers: dimer fatty acid (DFA),17 DFA-based diol (DDO), DFA-based diamine (DDA), DFA-based diisocyanate (DDI), and dimer acid methyl ester (DAME). Reproduced with permission from refs 29 (Copyright 2015, Scientific Research Publishing, Inc., Wuhan, PRC) and 17 (Copyright 2013, American Chemical Society, Washington, DC).

bonds make the fuel unstable for use in an engine.11 Dimeric acid methyl ester (DAME), which is produced via a Diel−Alder reaction of conjugate and unsaturated FAMEs (Figure 1), is a high-value specialty chemical that is widely used in polymer applications as an anticorrosive, plasticizer, and lubricant.12 However, there are few studies of the synthesis and application of elastomeric poly(ester)s using long-chain DAME for flexibility. Dimer fatty acid (DFA) is a long-chain dicarboxylic acid derived from unsaturated fatty acids (Figure 1), which can impart unique properties to the resulting polymers such as elasticity, flexibility, hydrolytic stability, hydrophobicity, and intrinsically low Tg.13,14 Theoretically, a mixture of epoxidized soybean oil (ESO) and DFA would polymerize to form hydroxyl-functionalized poly(ester) via the ring-opening of the epoxy group with −COOH groups, creating a pressuresensitive adhesive (PSA) system.15−17 The melt-blending of poly(L-lactide) (PLLA) with DFA-based linear thermoplastic poly(ester) (Mn = 36−64 kg mol−1) or poly(ester−amide) (Mw = 27 kg mol−1) was investigated as an efficient method to tailor PLLA toughness.18,19 Nonisocyanate poly(urethanes) (NIPU) were synthesized by reaction of carbonated soybean oil (CSBO) with amino-telechelic oligoamides derived from DFA to achieve thermoset and thermoplastics, respectively.20,21 Thermoplastic elastomer poly(etherimides) based on an aromatic dianhydride (e.g., 4,4′-oxidiphtalic anhydride (OPDA)) and a branched aliphatic dimer fatty acid-based diamine (DDA) as a replacement to traditional aromatic diamines, capable of healing at room temperature yet maintaining very high elastomeric-like mechanical properties (up to 6 MPa stress and 570% strain at break).22 Melt-phase polyaddition of DDA and diamine-terminated limonene dicarbonate-based prepolymer using carbonated 1,4-butanediol diglycidyl ether produces linear NIPU thermoplastics.23 Solvent-borne poly(ester urethane) coatings were prepared by thermally cross-linking the hydroxyl polyester polyols that contained homogeneously or heterogeneously distributed

sorbitol units with dimer fatty acid-based diisocyanate (DDI) as poly(isocyanates).24 The reactivity and region-selectivity of renewable building blocks, such as isosorbide, ethyl ester Llysine diisocyanate, and DDI, were studied for the synthesis of water-dispersible PU prepolymers.25 Segmented thermoplastic PUs composed of castor oil-based macrodiol, DDI, and 1,3propanediol as a bio-based chain extender, were investigated, indicating tailored mechanical properties that are tightly dependent on the overall crystallinity and high renewable carbon content.26 Copolyesters based on poly(butylene terephthalate) (PBT) (Mn = 18 kg mol−1) and a dimer fatty acid-based diol (DDO) were prepared by solid-state modification (SSM), demonstrating strong microphase-separated morphology.27 Random multiblock PUs were also synthesized via coupling of hydroxyl telechelic PLA oligomer (Mn = 7.2−8.1 kg mol−1) and DDObased polyol without evaluating the mechanical properties.28 Poly(lactide) (PLA), which is one of the most promising biopolymers, because of its unique properties such as biodegradability and biocompatibility,30 can be produced from annually renewable resources. However, one drawback of PLA is the brittleness of the homopolymer, which limits its application for the biomedical, packing, and textile industries, where tough mechanical behavior is required. Interestingly, multiblock copolymers have been shown to have superior mechanical properties, because of the ability of these block molecules to bridge multiple nanoscale domains.31,32 Hence, PLA-based alternate multiblock copolymer architectures for toughened plastics and thermoplastic elastomers were prepared from ABA triblock copolymers composed of PLA hard end blocks (A) connected by a soft, rubbery, and low-Tg segment (B), such as poly(ε-decalactone) (PDL),33 poly(ethylene-coethylethylene) (PE/EE),34 poly(butadiene) (PB),35 poly(trimethylene carbonate) (PTMC),36 and poly(ε-caprolactone) (PCL),37,38 followed by extension of the triblock chains using diisocyanate and diacid chloride. 8149


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Scheme 1. Synthesis of Semicrystalline [Poly(L-lactide)−Poly(dimer acid methyl ester-alt-poly(propylene glycol))−Poly(Llactide)]n Multiblock Copolymers

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RESULTS AND DISCUSSION Dimer Acid Methyl Ester (DAME). Biodiesel contains large amounts of unsaturated FAME (Figure 1), which can be converted into DAME through an acid-catalyzed Diels−Alder reaction between a dienophile and a conjugated diene.39 It was reported that dimerizing unsaturated fatty acid or FAME resulted in a mixture of isomers, including cyclic, acyclic, and aromatic structures.39 For this study, DAME was prepared via the dimerization of methyl oleate (MO) and methyl linoleate (CML), which was quantitatively conjugated, using a basetreated clay catalyst, with ∼70% conversion based on dimer (∼85 mol %) and trimer (∼15 mol %), followed by filtration, hydrogenation, and distillation for high purity (>97 mol % for dimer). The characterization, including molecular structures and molar masses of the synthesized DAME and the starting materials (MO and CML), was determined by 1H NMR spectroscopy and size exclusion chromatography (SEC) analysis, as shown in Figures S1a−d and S3a in the Supporting Information.40 Poly(propylene glycol) (PPG) is generally prepared via ring-opening polymerization of propylene oxide (PO) initiated by propylene glycol (PG) with a base catalyst; it is well-known that PPG is only terminated by secondary

We report the preparation of linear [poly(L-lactide)− poly(dimer acid methyl ester-alt-poly(propylene glycol))− poly(L-lactide)]n multiblock copolymers via coupling of hydroxyl telechelic ABA triblock copolymers with 4,4′methylenebis(phenyl isocyanate) (MDI), based on biodiesel, oligomeric diol, and L-lactide. The poly(dimer acid methyl ester-alt-poly(propylene glycol)) copolyesters for rubbery segments were synthesized with varying diol/diester molar ratio and diol molar masses over the entire range via an adapted two-step melt−polycondensation. We also show that both polymerization for the triblocks and coupling for the multiblocks can be conducted using tin(II) 2-ethylhexanoate (Sn(Oct)2) as a catalyst and that it is not necessary to isolate the intermediate during the process. Multiblock copolymers of the desired composition and high molar mass were obtained. The relationship among composition, morphology, thermal behavior, and mechanical properties of these multiblock copolymers was examined, demonstrating that the linear multiblocks could be processed for PSA application comparable to the petroleum-based commercial products, making these renewable materials attractive new thermoplastic elastomers. 8150


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Figure 2. Expanded region of the 1H NMR spectra of (a) DP1.0B rubbery, (b) LDP1.0BL triblock, and (c) (LDP1.0BL)2.7 multiblock copolymers, which is referred to the 13C{1H} NMR spectra (see Figure S2 in the Supporting Information).

the first stage, PPG (Mn = 425, 725, or 1000 g mol−1) and DAME (Mn = 592 g mol−1) were subjected to esterification with a [diol]/[diester] molar ratio of 1.1 or 1.2 under atmospheric pressure and nitrogen purging, in the absence of catalyst at 160 °C for 2 h. Methanol as a byproduct was continuously collected in a graduated vessel until reaction completion. Titanium(IV) butoxide (TBT) was added as a catalyst to promote the polycondensation reaction (second stage) under reduced pressure at 180−200 °C for 22 h. The telechelic hydroxyl PDP acted as a macroinitiator for the next PLLA polymerization and constituted a rubbery middle block in the poly(L-lactide)−poly(DAME-alt-PPG)−poly(L-lactide) (PLLA−PDP−PLLA). The chemical structure of the DP

hydroxyl end-groups since the nucleophilic reagent attacks the least-substituted position, in good agreement with 1H NMR spectra of the PPGs purchased for this study (Figure S1e in the Supporting Information).41,42 A sustainable route for the production of PO from bio-based glycerol via a PG intermediate was also proposed.43 Synthesis and Molecular Characterization. Poly(dimer acid methyl ester-alt-poly(propylene glycol)) (poly(DAME-altPPG)), abbreviated as DP rubbery copolymer (PDP), was obtained via a two-step melt polycondensation reaction of DAME and PPG, as shown in Scheme 1. To investigate the effect of PPG molar mass and [PPG]/[DAME] molar ratio on the molar mass of the synthesized DP rubber copolymers, in 8151


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Table 1. Characterization Data for DP Rubbery, LDPL Triblock, and (LDPL)n Multiblock Copolymers (PDP, PLLA−PDP− PLLA, and (PLLA−PDP−PLLA)n)a polymer DP0.4Ab DP0.4Bb DP0.7Ab DP0.7Bb DP1.0Ab DP1.0Bb LDP0.4ALm LDP0.4BLm LDP0.7ALm LDP0.7BLm LDP1.0ALm LDP1.0BLm (LDP0.4AL)1.3q (LDP0.4BL)1.9q (LDP0.7AL)1.4q (LDP0.7BL)2.9q (LDP1.0AL)2.5q (LDP1.0BL)2.7q

[C]0/[D]0

n

Mn (NMR) (kg mol−1)

Mw (SEC) (kg mol−1)f

1.1c 1.2c 1.1c 1.2c 1.1c 1.2c

16.3d 9.1d 10.4d 6.8d 7.6d 4.3d

16.5e 9.4e 14.1e 9.0e 12.8e 7.7e

33.0 25.0 18.6 20.5 26.4 22.7

49.5n 28.8n 43.8n 29.1n 38.4n 22.9n

1.0o 1.0o 1.0o 1.0o 1.0o 1.0o

23.2p 13.3p 19.9p 13.4p 18.0p 10.9p

39.9 29.4 28.6 29.7 31.3 29.1

1.0r 1.0r 1.0r 1.0r 1.0r 1.0r

1.3s 1.9s 1.4s 2.9s 2.5s 2.7s

30.2t 25.2t 27.8t 38.8t 44.9t 29.4t

67.4 76.8 49.7 118.0 94.0 101.7

Đf

Rubbery 4.7 4.1 3.0 3.0 2.8 2.8 Triblock 2.0 2.0 1.7 1.5 1.6 1.5 Multiblock 2.7 2.7 2.1 1.5 1.9 2.0

wPLLAg

Td,5% (°C)h

Tg (°C)i

316 302 313 306 313 305

−59 −60 −63 −65 −66 −63

0.31 0.31 0.32 0.30 0.30 0.29

216 213 210 221 205 206

−59, −57, −62, −61, −64, −62,

48 47 34 40 39 39

0.30 0.30 0.31 0.29 0.30 0.29

229 227 227 216 214 213

−59, −57, −58, −61, −63, −62,

56 54 44 45 42 40

Tm (°C)i

ΔHf (J g−1)j

XPLLA (%)k

D (nm)l

155 160 155 146 136 133

13.3 12.0 10.5 6.1 9.1 15.5

40.7 28.1 38.6 21.0 35.8 43.2

34 38 27 27 25 29

159 152 94

2.7 3.7 2.7

8.9 14.2 9.9

36 21 22 20 19 19

a

See the Experimental Section in the Supporting Information for synthetic details. bDP rubbery copolymers were abbreviated as DP copolymers (or PDP), and copolymerized with dimer acid methyl ester (DAME, Mn = 590 g mol−1) and poly(propylene glycol) (PPG, Mn = 425, 725, or 1000 g mol−1, which were designated 0.4, 0.7, or 1.0, respectively). The A and B designations indicate the stoichiometric ratio of PPG to DAME (1.1 for A, 1.2 for B). c[C]0 and [D]0 are the initial contents of PPG and DAME, respectively. dAverage number of DP repeating units in PDP, calculated using the following equation: nDP = [(AHc/4) × p/(AHa/2)], where AHc and AHa are the integration areas of the methylene protons (Hc) of DP repeating units and terminal methine protons of terminal PPG (Ha), and p is DAME conversion from methyl ester to ester, respectively, as determined by 13C NMR analysis. eCalculated using the following equation: Mn = nDP × (Mn of DP repeating unit) + (Mn of terminal PPG). fDetermined by size exclusion chromatography (SEC) in tetrahydrofuran at 40 °C, relative to poly(styrene) standards. gWeight fraction of PLLA (wPLLA). h5% weight loss (Td). evaluated by thermogravimetric analysis (TGA) at 10 °C min−1 under nitrogen. iDetermined by differential scanning calorimetry (DSC) (second heating cycle) at 10 °C min−1 under nitrogen. jHeat fusion for the triblock in J g−1. kPercent crystallinity based on the theoretical heat of fusion calculated for 100% crystalline PLLA (i.e., ΔHf° = 94.0 J g−1). lPrincipal domain spacing of the bulk sample determined by SAXS at room temperature. mSemicrystalline PLLA−PDP−PLLA triblock copolymers were abbreviated as LDPL triblock copolymers, or PLLA−PDP−PLLA. n [C]0 and [D]0 are the initial contents of L-lactide (LLA) and telechelic hydroxyl PDP macroinitiator, respectively. oAverage number of (PLLA− PDP−PLLA) units in LDPL triblock copolymers. pCalculated using the following equation: Mn = (Mn)by NMR of PDP for rubbery block + (Mn)by NMR of PLLA for hard block measured from the relative integrations of the PLLA repeating units and PLLA terminal unit. qThe semicrystalline (PLLA− PDP−PLLA)n multiblock copolymers were abbreviated as (LDPL)n multiblock copolymers, or (PLLA−PDP−PLLA)n. r[C]0 and [D]0 are the initial contents of isocyanate and telechelic hydroxyl PLLA−PDP−PLLA macroinitiator, respectively. sAverage number of (PLLA−PDP−PLLA) unit in (LDPL)n multiblock copolymers calculated from SEC-measured molar masses, expressed as the following equation: nLDPL = (Mn)by SEC of (PLLA− PDP−PLLA)n/(Mn)by SEC of (PLLA−PDP−PLLA). tCalculated using the following equation: nLDPL × (Mn)by NMR of PLLA−PDP−PLLA.

rubbery copolymers was determined by 1H NMR analysis (Figure 2). The chain connectivity between PPG and DAME was clearly determined by comparing the integration values for the methane and methylene peaks (Hb and Hc) at δ 5.02 and 2.27 adjacent to the repeating ester group in PDP, with an approximate ratio of 1:2 (see Figure 2a). To evaluate the conversion from DAME to PDP, the relative integration of methyl group at δ 3.67 in the unreacted methoxy groups of the dimer and the resulting polymers should be calculated. However, this could not be distinguished, because of overlap with other resonances. All DP copolymers were prepared with high conversion (p > 98%), as determined by comparing the relative integration between the methyl carbon at δ 50.9 (Cb″) of the unreacted terminal methoxy group and the methylene carbon at δ 34.0 (Cc′) adjacent to the repeating ester linkage in PDP, even if the intensity and integration of the peaks in the 13 C{1H} NMR spectrum did not indicate high accuracy, as shown in Figure S2 in the Supporting Information. The average

number of DP repeating units (nDP) in PDP could be calculated using the following equation: ⎛A ⎞ ⎛ p ⎞ nDP = ⎜⎜ Hc ⎟⎟ × ⎜ ⎟ ⎝ 4 ⎠ ⎝ AHa /2 ⎠

where AHc and AHa are the integration areas of the methylene protons (Hc) of DP repeating units and terminal methine protons (Ha) of terminal PPG in PDP, respectively. Molar masses of PDP (Mn = 7.7−16.5 kg mol−1) were also calculated using the following formula: (M n)PDP = nDP × (M n of DP repeating unit) + (M n of terminal PPG)

The values of nDP and (Mn)PDP gradually increased as the molar mass of PPG decreased from 1000 to 425 g mol−1, since the free movement of lower-molar-mass PPG is less restricted for polymerization, and as the [PPG]/[DAME] ratio, which was 8152


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Figure 3. Size-exclusion chromatography (SEC) data for dimer acid methyl ester (DAME) (trace a), poly(propylene glycol) (PPG) (traces b−d), DP rubbery (traces e, h, and k), LDPL triblock (traces f, i, and l), and (LDPL)n multiblock copolymers (traces g, j, and m).

related to the Carothers equation approached 1.44 Using SEC, relative to poly(styrene) (PS) standards, while DAME and PPG have fairly narrow molecular weight distributions (Đ < 1.1),40,42 the molecular weight distributions of the DP rubbery copolymers are broad (Đ > 2.8) (see Table 1), as expected for a step-growth polymerization technique (see Figure S3 in the Supporting Information and traces e, h, and k in Figure 3). Poly(L-lactide)−poly(DAME-alt-PPG)−poly(L-lactide), abbreviated as LDPL triblock copolymers (PLLA−PDP− PLLA), was prepared via the addition of L-lactide (LLA) to α,ω-dihydroxy telechelic PDP macroinitiators in the presence of Sn(Oct)2 at 110 °C, which were not purified in the one-pot sequential ROP. The molecular characteristics are summarized in Table 1. The block compositions with 29−31 wt % PLLA were readily controlled when PDP macroinitiator/LLA ratios of 1:23 to 1:50 were selected to prepare total PLLA molar masses of 3.1−6.7 kg mol−1. After completion of the polymerization, two new peaks for both the methine (He) at δ 4.36 beside the terminal hydroxyl group and the methine protons (Hd) at δ 5.16 of the ester repeating units in the PLLA block appeared, while the terminal methine protons (Ha) at δ 3.93 adjacent to the end hydroxyl group in the macroinitiator disappeared, indicating that there was efficient initiation of the monomer from the PDP chain ends (Figure 2b). The molar masses of the LDPL determined by 1H NMR spectroscopy were 10.9−23.2 kg mol−1, based on typical LLA conversion (∼95%). Compared to the PDP macroinitiator, the SEC chromatograms for the triblock showed an obvious shift to higher molar mass. The dispersity of the triblocks was much lower (Đ = 1.5−2.0) (Table 1), because of the controlled polymerization of LLA, showing no evidence of uninitiated PDP or PLLA homopolymer (see Figure S3, as well as traces f, i, and l in Figure 3). The (poly(L-lactide)−poly(DAME-alt-PPG)−poly(L-lactide)) n , abbreviated as (LDPL) n multiblock copolymers ((PLLA−PDP−PLLA)n), was synthesized by coupling α,ωhydroxy functionalized LDPL triblock copolymers using 4,4′-

methylenebis(phenyl isocyanate) (MDI) as a coupling agent without additional catalyst, which was not purified in one-pot sequential ROP. Six (LDPL)n multiblock copolymers were prepared from six premade LDPL triblock copolymers and their molecular characteristics are summarized in Table 1. The representative NMR spectrum of (PLLA−PDP−PLLA)n is shown in Figure 2c. The coupling reaction was supported by new proton peaks in the spectrum from the connector molecules; aromatic ring protons (Hg) and methylene protons (Hf) of MDI were present at δ 7.09 and 3.89. The average number of LDPL triblock units in the multiblock chain (nLDPL) was calculated by the ratio of the number-average molar mass determined using SEC (Mn)by SEC) of the multiblock to those of the triblock (Table 1). The molar masses of (LDPL)n based on (Mn)by NMR of PLLA−PDP−PLLA and nLDPL were 25.2−44.9 kg mol−1. The SEC chromatograms for the multiblocks also showed an obvious shift to higher molar mass with reasonable polydispersity values (Đ = 1.5−2.7) (see Table 1), compared to those of the PLLA−PDP−PLLA macroinitiators (see Figure S3, as well as traces g, j, and m in Figure 3). The chemical structures of DP rubbery, LDPL triblock, and (LDPL)n multiblock copolymers were also analyzed by Fourier transform infrared (FTIR) spectra. The synthesis of α,ωhydroxy telechelic PDP was confirmed by the detection of bands at 3480 and 1736 cm−1, corresponding to the absorption of the terminal hydroxyl groups and ester carbonyl groups, respectively, as shown in Figure 4a. For PLLA−PDP−PLLA, the two carbonyl absorption peaks located at 1760 and 1736 cm−1 correspond to the ester carbonyl groups of PLLA and PDP blocks (Figure 4b). In particular, in Figure 4c, the formation of new bands at 1600 and 1536 cm−1 confirmed the presence of urethane, which could be assigned to the absorption of carbonyl groups and N−H bending deformation combined with C−N asymmetric stretching. Moreover, small bands present at 3360 cm−1 could be assigned to the N−H stretching vibration of urethane groups and the absence of the 8153


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is typical for alternate copolymers with miscible composition, which form a single amorphous phase without microscale or nanoscale separation. Thus, the dependence on Tg and composition confirms the structure of PDP that is alternately copolymerized, as determined by NMR analysis. DSC traces of the LDPL triblock and (LDPL)n multiblock copolymers revealed two distinct glass transitions: one below −57 °C and the other above 39 °C, which were attributed by microphase separation into the PDP- and PLLA-rich domains, respectively. The Tg values of the triblock PLLA and PDP segments are in agreement with those predicted for PLLA homopolymer of similar molar mass and pure PDP.45 Upon further heating, the melting of PLLA crystals for LDPL triblock copolymers was clearly observed with Tm occurring at ∼133−155 °C. The degree of crystallinity (Xc) was calculated from the following expression: Xc =

Figure 4. FTIR spectra of (a) PDP, (b) PLLA−PDP−PLLA, and (c) (PLLA−PDP−PLLA)n.

(ΔHf (measured) − ΔHcc(measured)) /ΔHf°(PLLA) wf

where ΔHf(measured) is the endothermal melting peak area, ΔHcc(measured) the exothermal cold crystallization peak area, ΔHf° the heat of fusion for 100% crystalline PLLA (Hf° = 94 J g−1), and wf the weight fraction of the PLLA in the copolymer. The degree of crystallinity (21%−43%) in the triblock copolymers is lower than that of PLLA homopolymer with similar molar mass (see Table 1), which may be due to the fact that the covalently connected amorphous and rubbery PDL chain could hinder the crystallization of the PLLA blocks.46 The above-mentioned results for the two thermal transitions prove that the crystalline PLLA outer blocks are not combined but are incompatible or phase-separated in the rubbery PDL phase, which should be essential for achieving typical TPE behavior.47 However, it was clear that the magnitudes of the melting peak in the DSC scans of the multiblocks decreased or disappeared, along with a decrease or absence in Tm, compared to those of the triblocks (Figure 5 and Table 1). The PLLA blocks in LDPL are all dangling chains that have higher mobility for forming nuclei of crystal size than in the interior PLLA blocks in (LDPL)n. The restricted PLLA chain mobility of the loops and bridges in the multiblocks likely encumbers nucleation.34 The thermal stability of the DP rubbery, LDPL triblock, and (LDPL)n multiblock copolymers, including decomposition temperature at 5% weight loss (Td,5%), was investigated using TGA, as shown in Figure S4 in the Supporting Information and Table 1. The PPG homopolymers and DAME oligomer, as the units of PDP, were characterized by Td,5% at 191−244 and 291 °C, respectively. In comparison, only one transition in all PDP samples was observed in the TGA curves of all PDP samples. Moreover, it was shifted to a higher temperature (Td,5% = 302− 316 °C), compared to those of PPG and DAME. These results prove that the DP copolymers have typical characteristics for alternate copolymers with miscible composition, as also determined by DSC, and excellent thermal stability for rubberlike materials. Because the temperatures (Td,5%) of PLLA−PDP−PLLA and (PLLA−PDP−PLLA)n were in the range of 205−229 °C, the PLLA block prepared by Sn(Oct)2 catalysis could cause degradation via thermal transesterification. The microstructures of LDPL triblock and (LDPL) n multiblock copolymers were investigated using small-angle Xray scattering (SAXS) at ambient temperature. As indicated by the solid triangles in Figure 6, SAXS profiles of the samples

band at 2270 cm−1 confirmed no free isocyanate in (PLLA− PDP−PLLA)n. Thermal, Morphological, and Dynamic Mechanical Properties. The thermal properties of representative DP rubbery, LDPL triblock, and (LDPL)n multiblock copolymers, including transitions corresponding to glass transition (Tg) and melting (T m), were examined by differential scanning calorimetry (DSC) (Figure 5). It is known that the thermal

Figure 5. Representative DSC traces of DP1.0A, LDP1.0AL triblock, and (LDP1.0AL)2.5 multiblock copolymers. Arrows indicate glasstransition and melting temperatures (Tg and Tm, respectively) for rubber PDP-rich and semicrystalline PLLA-rich microdomains.

behavior of a polymer is affected by its thermal history. Therefore, all samples were subjected to a heat/cool/heat procedure described in the Experimental Section in the Supporting Information, and only the second heating scans were considered to give comparable results. The homo-PPG and DAME as the units of PDP were characterized by the Tg values at −73 and −54 °C, respectively. For Tg, only one transition, at −59 °C to −66 °C, was observed in the DSC curves of all PDP samples (see Table 1), which was shifted to higher and lower temperature from the Tg value of neat PPG and DAME, because of complete compatibility. Such behavior 8154


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109 Pa. Pronounced decreases in G′ occurred at approximately −58 °C, corresponding to the Tg values of the DP rubbery blocks (see Table 1); these transitions at −63 °C to −58 °C were also observed by DSC. Therefore, the Tg values obtained from DSC and DMA were in good agreement. As the temperature was increased to 140 °C, a plateau in the storage modulus was observed until the onset of a sharp decrease in G′ for the (LDPL)n multiblock copolymers, related to the order− disorder transition temperatures (TODT) and leading to domain disruption, depending on the wt % of the hard blocks, the molar masses of the blocks, and the solubility parameters (χ) between the rubbery and hard blocks.50 The effect of the average number and molar mass of the LDPL triblock unit in the multiblocks on the G′ and TODT has been studied in our work. The plateau moduli at 25 °C for the six multiblocks were 1.5−9.9 × 106 Pa (Figure 7), which were proportional to the

Figure 6. SAXS patterns at 25 °C for the LDPL triblock copolymers (dashed line) and (LDPL)n multiblock copolymers (solid line). The principal peaks at low q are indicated by solid triangles (▼).

exhibited broad single principal reflections (q*) at low q, indicating principle domain spacings in the range of 25−38 and 19−36 nm for the triblocks and multiblocks, respectively (Table 1). For all samples, a definitive assignment of morphology was not possible, because of broad basal reflections for higher order. This tendency for triblocks can be attributed to a broadening distribution of rubbery block lengths, which favors disordered microstructures.48 This tendency is also anticipated because the ability of the multiblock system to equilibrate into a long-range ordered system gradually becomes difficult, as the molar mass and the number of blocks per chain increases.49 The restricted mobility of the looped and bridged PLLA chains in the multiblocks is less likely to grow hard domains including crystals, compared to that of LDPL, which led to a decrease in the domain spacings. Therefore, the tendency toward reduced values of Tm, ΔHf, and D obtained from DSC and SAXS was in good agreement. Dynamic mechanical analysis (DMA) experiments showed the dynamic elastic properties of (PLLA−PDP−PLLA)n. The storage moduli (G′) of the samples as a function of temperature are shown in Figures S5 and S7 in the Supporting Information. Isochronal temperature ramps (ω = 1 rad s−1) were taken for all samples while heating at a rate of 3 °C min−1. As shown in the G′ plots, the elastic moduli of the multiblocks at low temperature (less than −60 °C) were constant at ∼2.0−3.0 ×

Figure 7. Viscoelastic properties (storage moduli, G′) for the (LDPL)n multiblock copolymers from −70 °C to 145 °C at a frequency of 1.00 rad s−1 with a strain of ∼1% and a ramp rate of 3 °C min−1. Arrows indicate the order−disorder transition temperatures (TODT) of the multiblock copolymers.

molecular weights ((Mw)by SEC) of the multiblocks affected by relatively lower molar masses ((Mn)by NMR) of the LDPL triblock copolymers caused by the [PPG]/[DAME] molar ratio of 1.2. Using the plateau modulus values of the (LDPL)n multiblock copolymers, assuming spherical glassy domains, to which Holden applied the Guth−Smallwood equation: G=

ρRT (1 + 2.5V + 14.1V 2) Me

where V is the hard phase volume fraction, ρ the density of rubbery phase, R the universal gas constant, T the temperature, and G the plateau storage modulus), the approximated entanglement molar masses (Me) for the DP rubbery copolymers in the six multiblocks were 0.7−4.2 kg mol−1 at 25 °C (see Table 2).51,52 Densities of 1.290 and 0.991 ± 0.017 8155


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Table 2. Mechanical Properties Data for (LDPL)n Multiblock Copolymers ((PLLA−PDP−PLLA)n)a and PLLA or PLASegmented Multiblock Thermoplastic Polyurethanes, as Previously Reported33−35,51,54 multiblock

f hard block

TODT (°C)

(LDP0.4AL)1.3 (LDP0.4BL)1.9 (LDP0.7AL)1.4 (LDP0.7BL)2.9 (LDP1.0AL)2.5 (LDP1.0BL)2.7 (LDL)4.9−6.0f

0.26b 0.26b 0.23b 0.24b 0.22b 0.27b 0.19−0.30

112c 128c 115c 102c 99c 82c 110−140

(LE/EEL)3.6h (LBL)1.7−3.9i (LDMSL)5.2−6.8j

0.70 0.60−0.90 0.50−0.60k

190 145−186

storage modulus, G′ (MPa)c

entanglement molar mass, Me (kg mol−1)d

± ± ± ± ± ±

For Elastomers 4.2 1.1 1.2 0.6 1.7 0.7

1.5 5.8 4.7 9.9 3.3 9.8

0.1 0.1 0.1 0.2 0.1 0.2

Young’s modulus, E (MPa)e

300% modulus (MPa)e

tensile strength, σb (MPa)e

strain at break, εb (%)e

1.2 ± 0.1 3.8 ± 0.1 5.3 ± 0.2 3.6 ± 0.1 7.9 ± 0.1 3.9 ± 0.1 0.6−2.2

1.9 ± 0.2 1.3 ± 0.1g 5.3 ± 0.2 3.6 ± 0.1 7.9 ± 0.1 3.9 ± 0.1

2.8 ± 0.1 1.5 ± 0.1 2.4 ± 0.1 5.1 ± 0.2 5.1 ± 0.1 3.9 ± 0.1 4.3−5.6

618 ± 11 289 ± 7 300 ± 24 2221 ± 86 1576 ± 106 1918 ± 225 1035−1470

23.5 21.4−30.4 3.1−5.9

632 29−953 74−310

For Plastics 549 192−1366 10−110

50−60l

a

See the Experimental Section in the Supporting Information for details. bVolume fractions of PLLA hard block calculated from densities of PLLA (1.290 g cm−1) and PDP (0.991 ± 0.017 g cm−1) at 25 °C and reported in ref 34. cTODT and G′ values at 25 °C determined by dynamic mechanical analysis (DMA) with rectangular torsion fixture. Oscillation test from −70 °C to 145 °C at 3 °C min−1, ω = 1.00 rad s−1, and γ = 1.0%. dCalculated using the Guth−Smallwood applied by Holden51 for block copolymers with spherical glassy domains: G = ρRT(1 + 2.5V + 14.1V2)/Me, where V is the hard-phase volume fraction, ρ the density of the rubbery phase, R the universal gas constant, T the temperature, and G the plateau storage modulus, the approximated entanglement molar mass (Me) for PDP in (PLLA−PDP−PLLA)n. eMechanical properties determined on an ASTM D1708 with microtensile bars and reported in refs 33−35 and ref 54. fData taken from ref 33. (LDL)4.9−6.0 represents (poly(L-lactide)−poly(εdecalactone)−poly(L-lactide))4.9−6.0 having (Mn)MR = 66−110 kg mol−1. gTensile stress at 100% strain. hData taken from ref 34. (LE/EEL)3.6 represents (poly(L-lactide)−poly(ethylene-co-ethylethylene)−poly(L-lactide))3.6 having (Mn)NMR = 38 kg mol−1 and σy (yield stress) = 27.7 MPa. i Data taken from ref 35. (LBL)1.7−3.9 represents (poly(L-lactide)−poly(butadiene)−poly(L-lactide))1.7−3.9 having (Mn)NMR = 41−77 kg mol−1 and σy (yield stress) = 11.4−37.2 MPa. jDatat taken from ref 54. (LDMSL)5.2−6.8 represents (poly(L-lactide)−poly(dimethylsiloxane)−poly(L-lactide))5.2−6.8 having (Mn)GPC (PS) = 95−99 kg mol−1 and σy (yield stress) = 3.0−6.0 MPa. kLLA composition defined as weight composition (wPLLA). lThese values were estimated from reference plots.54

g cm−3 were used for PLLA and PDP, respectively. The orderto-disorder transition was assumed to occur at the temperature at which G′ decreases abruptly, as indicated with arrows (TODT = 82−128 °C) (see Figures S5 and S7). In contrast, the measured TODT values gradually decreased as the molecular weights ((Mw)by SEC) of the (LDPL)n multiblock copolymers increased and were ascribed to relatively lower molar masses of LDPL triblock units prepared by both the effects of PPG molar mass and [PPG]/[DAME] molar ratio for smaller DP rubbery blocks (see Table 2). Tensile Properties and Adhesive Behaviors. Uniaxial extension experiments at room temperature were conducted to evaluate the mechanical properties of the (LDPL)n multiblock copolymers. Dog bone-shaped specimens prepared by solvent casting were elongated at a constant crosshead velocity of 130 mm min−1 until failure. The tensile data for multiblocks for a minimum of five repetitions are listed in Table 2 and representative engineering stress−strain (S−S) curves are shown in Figure 8. Unfortunately, since the films of LDPL triblock copolymers were not free-standing, it was not possible to prepare dog bone-shaped bars for comparison to (PLLA− PDP−PLLA)n. At low strains (50 000 min) with enhanced cohesive strength (Figure 9c). By comparison, tests on commercial duct tape, cellophane tape, and electrical tape under identical conditions gave peel adhesion values of 1.4−5.5 N cm−1 (without any adhesive residue) (Figure 9a), a tack force of 0.9−2.6 N, and a shear strength of ∼500−1100 min, except for the cellophane tape (which had shear strength of >50 000 min (Figures 9b and 9c).53,58 Taken together, the self-adhesive properties of the sustainable PSA systems including (PLLA−PDP−PLLA)2.7 multiblock elastomer, RE tackifier, and DAME plasticizer were not only controllable but also competitive with commercial PSA tapes.

The adhesion behaviors of two PSA systems, including the renewable (LDPL)n multiblocks as a base elastomer, rosin ester (RE) tackifier, and DAME plasticizer having the identical structure to portion of of the base elastomers, were investigated by 180° peel, probe tack, and shear static adhesion on stainless panel, as shown in Figure 9.55 The peel test determines the force needed to tear a 25-mm-wide strip of PET tape from a solid substrate at a constant speed, expressed herein in terms of N cm−1. In addition, tack (N) is the ability to control the instant formation of a bonding interaction between adhesive and substrate when they are brought into contact, and shear strength (min) is the internal resistance of an adhesive to creeping under an applied load.56,57 Peel adhesion was developed by increasing the content of (LDP1.0BL) 2.7 multiblock copolymer, with relatively superior tensile properties (E = 3.9 MPa, σb = 3.9 MPa, and εb = 1918%) from 35 wt % to 45 wt % in the PSA system, which eventually reached peel strengths (3.1 N cm−1) with no residue (see Figure 9a), demonstrating that the cohesive strengths of the PSAs was high and tunable. Since the amount of rosin ester (RE) tackifier was constant with 50% in the two PSA formulations, relatively high tack forces (∼2.0 N) were observed, regardless of the content of the multiblock elastomer and DAME plasticizers (Figure 9b). Increasing the amount of (LDP1.0BL)2.7 multiblock

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CONCLUSION We applied a multiblock copolymer strategy to a poly(Llactide)−poly(dimer acid methyl ester-alt-poly(propylene glycol)) (PLLA−PDP) system to produce sustainable thermoplastic elastomers that can be used in an extended range of pressure-sensitive adhesive applications. The PLLA−PDP multiblock copolymers were synthesized using a three-stage procedure: (i) DP rubbery copolymers were synthesized through step-growth melt polycondensation of poly(propylene 8157


Research Article

ACS Sustainable Chemistry & Engineering DSC = differential scanning calorimetry TGA = thermogravimetric analysis SAXS = small-angle X-ray scattering DMA = dynamic mechanical analysis

glycol) and dimer acid methyl ester (DAME) derived from biodiesel, (ii) PLLA−PDP−PLLA (LDPL) triblock copolymers were prepared using ring-opening polymerization of L-lactide, and (iii) synthesized LDPL triblock copolymers were connected with the chain extender, 4,4′-methylenebis(phenyl isocyanate) (MDI). This multiblock method allowed us to access the desired morphologies by controlling the volume fraction of PLLA ( f PLLA = 0.22−0.27). The bulk properties of the triblock and multiblock polymers were analyzed by DSC, TGA, SAXS, DMA, and uniaxial extension experiments. Microphase separation was suggested by DSC data for both the triblock and multiblock polymers and corroborated by SAXS. The (LDPL)n multiblock architectures in this study had TODT values below 130 °C. The multiblocks that were connected by low-molar-mass LDPL triblock displayed impressive tensile toughness, compared to precursor triblocks with no free-standing thin films, which was attributed to the formation of bridged PLLA hard end blocks. A renewable rosin ester and DAME derived from biodiesel were formulated with varying amounts (35 and 45 wt %) of multiblocks to tailor or control the PSA properties. Probe tack, peel adhesion, and static shear strength tests were performed to evaluate the selfadhesive properties. The results were consistent and exhibited considerable adhesive performance.

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Variables

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REFERENCES

(1) Knothe, G., Van Gerpen, J., Krahl, J., Eds. The Biodiesel Handbook; AOCS Press: Champaign, IL, 2005. (2) Demirbas, A. Biodiesel production via rapid transesterification. Energy Sources, Part A 2008, 30, 1830−1834. (3) Meher, L. C.; Vidya Sagar, D.; Naik, S. N. Technical aspects of biodiesel production by transesterification−a review. Renewable Sustainable Energy Rev. 2006, 10, 248−268. (4) Ma, F.; Hanna, M. A. Biodiesel production: A review. Bioresour. Technol. 1999, 70, 1−15. (5) European Biofuels Technology Platform. Available via the Internet at: http://www.biofuelstp.eu/factsheets/fame-fact-sheet.pdf (accessed Feb. 28, 2017). (6) Cole-Hamilton, D. J. Nature’s polyethylene. Angew. Chem., Int. Ed. 2010, 49, 8564−8566. (7) Sibeijn, M.; Poels, E. K.; Bliek, A.; Moulijn, J. A. Technological and economical aspects of the metathesis of unsaturated ester. J. Am. Oil Chem. Soc. 1994, 71, 553−561. (8) Pugh, R. I.; Drent, E.; Pringle, P. G. Tandem isomerisation− carbonylation catalysis: highly active palladium(II) catalysts for the selective methoxycarbonylation of internal alkenes to linear esters. Chem. Commun. 2001, 1476−1477. (9) Jiménez-Rodriguez, C.; Eastham, G. R.; Cole-Hamilton, D. J. Dicarboxylic acid esters from the carbonylation of unsaturated esters under mild conditions. Inorg. Chem. Commun. 2005, 8, 878−881. (10) Quinzler, D.; Mecking, S. Linear semicrystalline polyesters from fatty acids by complete feedstock molecule utilization. Angew. Chem., Int. Ed. 2010, 49, 4306−4308. (11) Liu, S.; Zhou, H.; Yu, S.; Xie, C.; Liu, F.; Song, Z. Dimerization of fatty acid methyl ester using Brönsted−Lewis acidic ionic liquid as catalyst. Chem. Eng. J. 2011, 174, 396−399. (12) Chen, J.; Li, X.; Wang, Y.; Huang, J.; Li, K.; Nie, X.; Jiang, J. Epoxidized dimeric acid methyl ester derived from rubber seed oil and its application as secondary plasticizer. J. Appl. Polym. Sci. 2016, 133, 43668. (13) Hill, K. Fats and oils as oleochemical raw materials. Pure Appl. Chem. 2000, 72, 1255−1264. (14) Maisonneuve, L.; Lebarbé, T.; Grau, E.; Cramail, H. Structure− properties relationship of fatty acid-based thermoplastics as synthetic polymer mimics. Polym. Chem. 2013, 4, 5472−5517. (15) Li, A.; Li, K. Pressure-sensitive adhesives based on epoxidized soybean oil and dicarboxylic acids. ACS Sustainable Chem. Eng. 2014, 2, 2090−2096. (16) Torron, S.; Hult, D.; Pettersson, T.; Johansson, M. Tailoring soft polymer networks based on sugars and fatty acids toward pressure sensitive adhesive applications. ACS Sustainable Chem. Eng. 2017, 5, 2632. (17) Vendamme, R.; Eevers, W. Sweet solution for sticky problems: chemoreological design of self-adhesive gel materials derived from lipid biofeedstocks and adhesion tailoring via incorporation of isosorbide. Macromolecules 2013, 46, 3395−3405. (18) Lebarbé, T.; Grau, E.; Gadenne, B.; Alfos, C.; Cramail, H. Synthesis of fatty acid-based polyesters and their blends with poly(Llactide) as a way to tailor PLLA toughness. ACS Sustainable Chem. Eng. 2015, 3, 283−292.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b01801. Annexure S1 and Figures S1−S5 (PDF)

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f i = volume fraction of component i Td = thermal degradation temperature Tg = glass-transition temperature Tm = melting temperature TODT = order-to-disorder transition temperature

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (Y.-W. Kim). *E-mail: [email protected] (J. Shin). ORCID

Sangjun Lee: 0000-0002-2227-9212 Jihoon Shin: 0000-0002-8274-741X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS J. Shin acknowledges that this work was financially supported by the R&D Center for Valuable Recycling (Global-Top Environmental Technology Development Program) through a grant from Ministry of Environment of Republic Korea (Project No. 2016002240003). Experiments at Pohang Accelerator Laboratory (PAL) were supported in part by the Ministry of Science, ICT and Future Planning of Korea and POSTECH.

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ABBREVIATIONS DAME = dimer acid methyl ester PPG = poly(propylene glycol) DP = poly(DAME-alt-PPG) LPDL = poly(L-lactide)−poly(DAME-alt-PPG)−poly(L-lactide) triblock polymer (LDPL)n = (poly(L-lactide)−poly(DAME-alt-PPG)−poly(Llactide))n multiblock polymer TPE = thermoplastic elastomers PSA = pressure sensitive adhesive 8158


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ACS Sustainable Chemistry & Engineering (19) Lebarbé, T.; Grau, E.; Alfos, C.; Cramail, H. Fatty acid-based thermoplastic poly(ester-amide) as toughening and crystallization improver of poly(L-lactide). Eur. Polym. J. 2015, 65, 276−285. (20) Poussard, L.; Mariage, J.; Grignard, B.; Detrembleur, C.; Jérôme, C.; Calberg, C.; Heinrichs, B.; De Winter, J.; Gerbaux, P.; Raquez, J.M.; Bonnaud, L.; Dubois, Ph. Non-isocyanate polyurethanes from carbonated soybean oil using monomeric or oligomeric diamines to achieve thermosets or thermoplastics. Macromolecules 2016, 49, 2162− 2171. (21) Grignard, B.; Thomassin, J.-M.; Gennen, S.; Poussard, L.; Bonnaud, L.; Raquez, J.-M.; Dubois, P.; Tran, M.-P.; Park, C. B.; Jerome, C.; Detrembleur, C. CO2-blown microcellular non-isocyanate polyurethane (NIPU) foams: from bio- and CO2-sourced monomers to potentially thermal insulating materials. Green Chem. 2016, 18, 2206−2215. (22) Susa, A.; Bose, R. K.; Grande, A. M.; van der Zwaag, S.; Garcia, S. J. Effect of the dianhydride/branched diamine ratio on the architecture and room temperature healing behavior of polyetherimides. ACS Appl. Mater. Interfaces 2016, 8, 34068−34079. (23) Schimpf, V.; Ritter, B. S.; Weis, P.; Parison, K.; Mülhaupt, R. High purity limonene dicarbonate as versatile building block for sustainable non-isocyanate polyhydroxyurethane thermosets and thermoplastics. Macromolecules 2017, 50, 944−955. (24) Gustini, L.; Lavilla, C.; Finzel, L.; Noordover, B. A. J.; Hendrix, M. M. R. M.; Koning, C. E. Sustainable coatings from bio-based, enzymatically synthesized polyesters with enhanced functionalities. Polym. Chem. 2016, 7, 6586−6597. (25) Li, Y.; Noordover, B. A. J.; van Benthem, R. A. T. M.; Koning, C. E. Reactivity and regio-selectivity of renewable building blocks for the synthesis of water-dispersible polyurethane prepolymers. ACS Sustainable Chem. Eng. 2014, 2, 788−797. (26) Calvo-Correas, T.; Martin, M. D.; Retegi, A.; Gabilondo, N.; Corcuera, M. A.; Eceiza, A. Synthesis and characterization of polyurethanes with high renewable carbon content and tailored properties. ACS Sustainable Chem. Eng. 2016, 4, 5684−5692. (27) Gubbels, E.; Jasinska-Walc, L.; Merino, D. H.; Goossens, H.; Koning, C. Solid-state modification of poly(butylene terephthalate) with a bio-based fatty acid dimer diol furnishing copolyesters with unique morphologies. Macromolecules 2013, 46, 3975−3984. (28) Cavallo, D.; Gardella, L.; Soda, O.; Sparnacci, K.; Monticelli, O. Fully bio-renewable multiblocks copolymers of poly(lactide) and commercial fatty acid-based polyesters polyols: Synthesis and characterization. Eur. Polym. J. 2016, 81, 247−256. (29) Adekunle, K. F. A review of vegetable oil-based polymers: Synthesis and applications. Open J. Polym. Chem. 2015, 5, 34−40. (30) Belgacem, M. N.; Gandini, A. Monomers, Polymers and Composites from Renewable Resources; Elsevier: Amsterdam, 2008. (DOI: 10.1016/B978-008045316-3.00026-0.) (31) Hermel, T. J.; Hahn, S. F.; Chaffin, K. A.; Gerberich, W. W.; Bates, F. S. Role of molecular architecture in mechanical failure of glassy/semicrystalline block copolymers: CEC vs CECEC lamellae. Macromolecules 2003, 36, 2190−2193. (32) Ryu, C. Y.; Ruokolainen, J.; Fredrickson, G. H.; Kramer, E. J.; Hahn, S. F. Chain architecture effects on deformation and fracture of block copolymers with unentangled matrices. Macromolecules 2002, 35, 2157−2166. (33) Martello, M. T.; Schneiderman, D. K.; Hillmyer, M. A. Synthesis and melt processing of sustainable poly(ε-decalactone)-block-poly(lactide) multiblock thermoplastic elastomers. ACS Sustainable Chem. Eng. 2014, 2, 2519−2526. (34) Panthani, T. R.; Bates, F. S. Crystallization and mechanical properties of Poly(L-lactide)-based rubbery/semicrystalline multiblock copolymers. Macromolecules 2015, 48, 4529−4540. (35) Lee, I.; Panthani, T. R.; Bates, F. S. Sustainable poly(lactide-bbutadiene) multiblock copolymers with enhanced mechanical properties. Macromolecules 2013, 46, 7387−7398. (36) Pospiech, D.; Komber, H.; Jehnichen, D.; Häussler, L.; Eckstein, K.; Scheibner, H.; Janke, A.; Kricheldorf, H. R.; Petermann, O.

Multiblock copolymers of L-lactide and trimethylene carbonate. Biomacromolecules 2005, 6, 439−446. (37) Cohn, D.; Salomon, A. H. Designing biodegradable multiblock PCL/PLA thermoplastic elastomers. Biomaterials 2005, 26, 2297− 2305. (38) Peponi, L.; Navarro-Baena, I.; Sonseca, A.; Gimenez, E.; Marcos-Fernandez, A.; Kenny, J. M. Synthesis and characterization of PCL−PLLA polyurethane with shape memory behavior. Eur. Polym. J. 2013, 49, 893−903. (39) (a) Paschke, R. F.; Peterson, L. E.; Wheeler, D. H. Dimer acid structures. the thermal dimer of methyl 10-trans, 12-trans, linoleate. J. Am. Oil Chem. Soc. 1964, 41, 723−727. (b) Vendamme, R.; Olaerts, K.; Gomes, M.; Degens, M.; Shigematsu, T.; Eevers, W. Interplay between viscoelastic and chemical tunings in fatty-acid-based polyester adhesives: engineering biomass toward functionalized step-growth polymers and soft networks. Biomacromolecules 2012, 13, 1933−1944. (c) Pomelli, C. S.; Ghilardi, T.; Chiappe, C.; de Angelis, A. R.; Calemma, V. Alkylation of Methyl Linoleate with Propene in Ionic Liquids in the Presence of Metal Salts. Molecules 2015, 20, 21840− 21853. (40) The number-average molar mass (Mn) of DAME was 379 g mol−1 (Đ = 1.02), which was determined by SEC using THF as an eluent and PS standards. (41) Hanna, J. G.; Siggia, S. Primary and secondary hydroxyl group content of polypropylene glycols. J. Polym. Sci. 1962, 56, 297−304. (42) The number-average molar masses (Mn) of PPG 425, 735, and 1000 were 291, 686, and 936 g mol−1 (Đ = 1.02, 1.05, and 1.05) (see Figures 3b−d), respectively, which were determined by SEC using THF as an eluent and PS standards. (43) Yu, Z.; Xu, L.; Wei, Y.; Wang, Y.; He, Y.; Xia, Q.; Zhang, X.; Liu, Z. A new route for the synthesis of propylene oxide from bio-glycerol derivated propylene glycol. Chem. Commun. 2009, 3934−3936. (44) Carothers, W. H. Polymers and polyfunctionality. Trans. Faraday Soc. 1936, 32, 39−49. (45) Jamshidi, K.; Hyon, S.-H.; Ikada, Y. Thermal characterization of polylactides. Polymer 1988, 29, 2229−2234. (46) Peponi, L.; Navarro-Baena, I.; Báez, J. E.; Kenny, J. M.; MarcosFernández, A. Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers. Polymer 2012, 53, 4561−4568. (47) Lee, S.; Lee, K.; Jang, J.; Choung, J. S.; Choi, W. J.; Kim, G.-J.; Kim, Y.-W.; Shin, J. Sustainable poly(ε-decalactone)−poly(L-lactide) multiarm star copolymer architectures for thermoplastic elastomers with fixed molar mass and block ratio. Polymer 2017, 112, 306−317. (48) Fredrickson, G. H.; Milner, S. T.; Leibler, L. Multicritical phenomena and microphase ordering in random block copolymer melts. Macromolecules 1992, 25, 6341−6354. (49) Krause, S. Microphase separation in block copolymers. Zeroth approximation including surface free energies. Macromolecules 1970, 3, 84−86. (50) Tse, M. F. Studies of triblock copolymer-tackifying resin interactions by viscoelasticity and adhesive performance. J. Adhes. Sci. Technol. 1989, 3, 551−570. (51) Holden, G. Properties and Applications of Elastomeric Block Copolymers. In Block and Graft Polymerization; Ceresa, R. J., Ed; John Wiley & Sons: New York, 1972; Chapter 6. (52) Guth, E. Theory of Filler Reinforcement. J. Appl. Phys. 1945, 16, 20−25. (53) Lee, S.; Lee, K.; Kim, Y.-W.; Shin, J. Preparation and characterization of a renewable pressure-sensitive adhesive system derived from ε-decalactone, L-lactide, epoxidized soybean oil, and rosin ester. ACS Sustain. ACS Sustainable Chem. Eng. 2015, 3, 2309− 2320. (54) Ho, C.-H.; Wang, C.-H.; Lin, C.-I; Lee, Y.-D. Synthesis and characterization of (AB)n-type poly(L-lactide)−poly(dimethyl siloxane) multiblock copolymer and the effect of its macrodiol composition on urethane formation. Eur. Polym. J. 2009, 45, 2455−2466. (55) Czech, Z. Synthesis of removable and repositionable waterborne pressure-sensitive adhesive acrylics. J. Appl. Polym. Sci. 2005, 97, 886−892. 8159


Research Article

ACS Sustainable Chemistry & Engineering (56) Benedek, I. Pressure-Sensitive Adhesives and Applications, 2nd Edition; Marcel Dekker: New York, 2004; pp 429−477. (57) Pocius, A. V. Adhesion and Adhesives Technology: An Introduction, 1st Edition; Hanser−Gardner: Cincinnati, OH, 1997; pp 251−259. (58) Shin, J.; Martello, M. T.; Shrestha, M.; Wissinger, J. E.; Tolman, W. B.; Hillmyer, M. A. Pressure-sensitive adhesives from renewable triblock copolymers. Macromolecules 2011, 44, 87−94.

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Multiblock Thermoplastic Elastomers Derived from Biodiesel, Poly

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