Alternating Isotactic Polyhydroxyalkanoates via Site- and Stereoselective Polymerization of Unsymmetrical Diolides
Alternating Isotactic Polyhydroxyalkanoates via Site- and Stereoselective Polymerization of Unsymmetrical Diolides
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通过不对称二烯化合物的位点和立体选择性聚合制备交替全同立构聚羟基脂肪酸酯
DOI：
10.1021/jacs.2c08791
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发表时间：
2022
影响因子：
15
通讯作者：
Chen, Eugene Y.-X.
中科院分区：
文献类型：
--
作者：
Zhang, Zhen;Shi, Changxia;Scoti, Miriam;Tang, Xiaoyan;Chen, Eugene Y.-X.
天然生产的可生物降解聚羟基脂肪酸酯 (PHA) 有望成为不可再生/可降解塑料的更可持续的替代品，但生物 PHA 的立体微观结构严格限于全同立构 (R) 聚合物或无规序列共聚物。通过环（二）酯的催化开环聚合（ROP）进行化学合成可以方便地获得各种 PHA 微观结构，包括具有确定的共聚单体序列和立构规整度的结构。然而，现有方法尚未实现交替全同立构PHA的合成。在这里，我们报告了不对称二取代八元二内酯（rac-8DLR1-R2）的设计及其使用离散手性催化剂的位点和立体选择性ROP，从而能够合成交替的全同立构PHA，聚（3-羟基丁酸酯-alt-3-羟基戊酸酯）（alt-P3HBV）和聚（3-羟基丁酸酯-alt-3-羟基庚酸酯） (alt-P3HBHp)，具有高定量 (>99%) 交替和全同立构规整度，Mn 高达 113 kDa，Đ= 1.01。此类PHA的物理性质基本上由主链序列交替程度和立构规整度决定，范围从无定形到半结晶材料。相对于均聚物，Thealt-P3HBV 显示出显着改善的机械性能。有趣的是，通过动力学解析 ROP ofrac-8DLMe-Et 合成的对映体 (R)-alt-P3HBV 和 (S)-alt-P3HBV 形成立体复合物，其 Tm 显着增强（53 °C），而对映体均聚物则不形成立体复合物。
Naturally produced, biodegradable polyhydroxyalkanoates (PHAs) promise more sustainable alternatives to nonrenewable/degradable plastics, but biological PHA’s stereomicrostructures are strictly confined to isotactic (R)-polymers or copolymers of random sequences. Chemical synthesis via catalyzed ring-opening polymerization (ROP) of cyclic (di)esters offers expedient access to diverse PHA microstructures, including those with defined comonomer sequences and tacticities. However, the synthesis of alternating isotactic PHAs has not been achieved by the existing methodologies. Here, we report the design of unsymmetrically disubstituted eight-membered diolides (rac-8DLR1-R2) and their site- and stereoselective ROP with discrete chiral catalysts, enabling the synthesis of alternating isotactic PHAs, poly(3-hydroxybutyrate-alt-3-hydroxyvalerate) (alt-P3HBV) and poly(3-hydroxybutyrate-alt-3-hydroxyheptanoate) (alt-P3HBHp), with high to quantitative (>99%) alternation and isotacticity andMnup to 113 kDa andĐ= 1.01. Physical properties of such PHAs are substantially determined by the degree of backbone sequence alternation and tacticity, ranging from amorphous to semi-crystalline materials. Thealt-P3HBV shows significantly improved mechanical performance relative to the constituent homopolymers. Intriguingly, enantiomeric (R)-alt-P3HBV and (S)-alt-P3HBV, synthesized by kinetically resolved ROP ofrac-8DLMe-Et, form a stereocomplex with a significantly enhancedTm(by 53 °C), while the enantiomeric homopolymers do not form a stereocomplex.