Stereocomplex Formation between Enantiomeric Substituted Poly(lactide)s: Blends of Poly[(S)-2-hydroxybutyrate] and Poly[(R)-2-hydroxybutyrate]
Stereocomplex Formation between Enantiomeric Substituted Poly(lactide)s: Blends of Poly[(S)-2-hydroxybutyrate] and Poly[(R)-2-hydroxybutyrate]
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DOI：
10.1021/ma9015483
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发表时间：
2009-09
期刊：
影响因子：
5.5
通讯作者：
H. Tsuji;A. Okumura
中科院分区：
文献类型：
--
作者：
H. Tsuji;A. Okumura
介绍。当具有不同立构规整度或构型的聚合物之间的相互作用优于具有相同立构规整度或构型的聚合物之间的相互作用时，发生前一聚合物对的立体选择性缔合。这种缔合被描述为立体络合或立体络合物形成，并且据报道一些光学非活性全同立构和间同立构聚合物对以及光学活性S-和R-聚合物(或L-和D-聚合物)形成立体络合物。 1-4 对于对映体光学活性聚酯共混物，Grenier 和 Prud’homme 首先报道了 S-和 R-聚（R-甲基-R-乙基-β-丙内酯）（PMEPL）之间的立体络合。 5 PMEPL 的单体 2-羟甲基-2-甲基-丁酸是一种带有手性 R 碳的 β-羟基羧酸。后来，Ikada 等人。发现聚[(S)-丙交酯](PSLA) 和聚[(R)-丙交酯](PRLA) 之间存在立体络合。 6 聚丙交酯(PLA) 的单体乳酸（2-羟基丙酸）是一种带有手性R-碳的R-羟基羧酸。尽管这些聚酯 PMEPL 和 PLA 具有手性 R-碳，但 Voyer 和 Prud’homme 报道了 S-和 R-聚酯与手性 β-碳、具有不同侧基（含氯化物）的聚（β-丙内酯）之间的立体络合。 7 这些聚合物的单体是具有手性 β-碳的 β-羟基羧酸。对映体光学活性聚酯的立体络合物的熔融温度（Tm）远高于纯R-或S-聚酯，并且其晶格与聚酯成分完全不同。 1-4, 8 关于可生物降解的聚酯立体复合物，人们对PLA立体复合物进行了深入研究，1-4可以通过各种方法形成，包括立体嵌段共聚物的结晶。 9-14 另一方面，聚(2-羟基丁酸酯)[P(2HB)]，即聚(2-羟基丁酸)或聚(2-羟基丁酸)可以由R-羟基羧酸与手性R-碳(2-羟基丁酸)合成。 P(2HB)具有PLA的结构，其甲基被乙基取代（图1）。 P (2HB) 易于水解降解，因此可用作生物医学、制药和环境应用的可生物降解材料。 15 贝克等人。集中合成了包括 P (2HB) 在内的多种取代 PLA，并研究了它们的物理性能和热降解。 16-18 在他们的研究中，大多数合成的聚合物都是外消旋的、光学非活性的和不可结晶的。在本研究中，我们通过合成对映体、光学活性和可结晶的聚[(S)-2-羟基丁酸酯][P(S-2HB)]和聚[(R)-2-羟基丁酸酯][P(R-2HB)]。 传统的缩聚方法，并在此首次报告了 P (S-2HB) 和 P (R-2HB) 之间的立体络合。实验部分。材料。 (S)-和(R)-2-羟基丁酸缩聚合成P(S-2HB)[数均分子量(Mn)= 3.3 × 103 g mol-1，重均分子量(Mw)/Mn= 3.9]和P(R-2HB)(Mn= 3.6 × 103 g mol-1，Mw/Mn= 3.7) (羟基丁酸)(g97. 0%，对映体比例g 99:1，Sigma-Aldrich Co.)分别根据先前文献纯化19和20、21。
Introduction. When the interaction between polymers having different tacticities or configurations prevails over that between those having the same tacticity or configuration, a stereoselective association of the former polymer pair takes place. Such association is described as stereocomplexation or a stereocomplex formation and some pairs of optically inactive isotactic and syndiotactic polymers and of optically activeS-andR-polymers (orL-and D-polymers) are reported to form a stereocomplex. 1-4 With respect to enantiomeric, optically active polyester blends, Grenier and Prud’homme first reported stereocomplexation between S-and R-poly (R-methyl-R-ethyl-β-propiolactone) s (PMEPLs). 5 The monomer of PMEPL, 2-hydroxymethyl-2-methyl-butanoic acid, is a β-hydroxycarboxylic acid with a chiral R-carbon. Later, Ikada et al. found stereocomplexation between poly [(S)-lactide](PSLA) and poly [(R)-lactide](PRLA). 6 The monomer of poly (lactide)(PLA), lactic acid (2-hydroxypronanoic acid), is an R-hydroxycarboxylic acid with a chiral R-carbon. Although these polyesters, PMEPL and PLA, have chiral R-carbons, Voyer and Prud’homme reported stereocomplexation between S-andR-polyesters with chiralβ-carbons, poly (β-proriolactone) s with different side groups containing chlorides. 7 The monomers of these polymers are β-hydroxycarboxylic acids with chiral β-carbons. The stereocomplex of enantiomeric, optically active polyesters has a melting temperature (Tm) much higher than that of either pure R-or S-polyesters and a crystalline lattice which is completely different from that of constituent polyesters. 1-4, 8 In regard to biodegradable polyester stereocomplexes, intensive studies have been carried out for the PLA stereocomplex, 1-4 which can be formed by various methods, including the crystallization of stereoblock copolymers. 9-14 On the other hand, poly (2-hydroxybutyrate)[P (2HB)], ie, poly (2-hydroxybutyric acid) or poly (2-hydroxybutanoic acid) can be synthesized from R-hydroxycarboxylic acid with a chiral R-carbon (2-hydroxybutanoic acid). P (2HB) has the structure of PLA, the methyl group of which is substituted with an ethyl group (Figure 1). P (2HB) is susceptible to hydrolytic degradation and, therefore, can be utilized as a biodegradable material for biomedical, pharmaceutical, and environmental applications. 15 Baker et al. intensively synthesized a wide variety of substituted PLAs, including P (2HB), and investigated their physical properties and thermal degradation. 16-18 In their study, most of the synthesized polymers were racemic, optically inactive, and noncrystallizable.In the present study, we synthesized enantiomeric, optically active, and crystallizable poly [(S)-2-hydroxybutyrate][P (S-2HB)] and poly [(R)-2-hydroxybutyrate][P (R-2HB)] by a conventional polycondensation method and herewith first report stereocomplexation between P (S-2HB) and P (R-2HB). Experimental Section. Materials. The P (S-2HB)[numberaverage molecular weight (Mn)= 3.3 Â 103 g mol-1, weightaverage molecular weight (Mw)/Mn= 3.9] and P (R-2HB)(Mn= 3.6 Â 103 g mol-1, Mw/Mn= 3.7) were synthesized by polycondensation of (S)-and (R)-2-hydroxybutanoic acids (hydroxybutyric acids)(g97. 0%, enantiomeric ratio g 99: 1, Sigma-Aldrich Co.), respectively, 19 and purified20, 21 according to the previous literature.