Crystalline aliphatic polyesters from eight‐membered cyclic (di)esters
Crystalline aliphatic polyesters from eight‐membered cyclic (di)esters
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DOI：
10.1002/pol.20220418
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发表时间：
2022-10
影响因子：
3.4
通讯作者：
X. Tang;Changxia Shi;Zhen Zhang;E. Chen
中科院分区：
文献类型：
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作者：
X. Tang;Changxia Shi;Zhen Zhang;E. Chen
内酯或环状（二）酯的开环聚合（ROP）是生产结构明确的高分子量（生物）可降解脂肪族聚酯的有效方法。虽然各种环尺寸的内酯的 ROP 已被广泛研究，但最简单的八元内酯 7-庚内酯 (7-HL) 的 ROP 尚未有使用金属基催化剂的报道。因此，本文报道了 7-HL 通过金属催化的配位插入聚合反应生成相应的高分子量聚酯，聚（7-羟基庚酸酯）（P7HHp）。所得的 P7HHp 是一种半结晶材料，Tm 为 68°C，比七元内酯衍生的聚（ε-己内酯）高约 10°C。机械测试表明，P7HHp 是一种坚硬而坚韧的塑料，断裂伸长率 >670%。通过 7-HL 与八元环二酯、外消旋二甲基二内酯 (rac-8DLMe) 的立体选择性共聚，获得了具有较高 Tm 值的 P7HHp 基聚酯，已知可产生高 Tm 聚 (3-羟基丁酸酯) (P3HB)。值得注意的是，催化剂在 1/1 共聚单体混合物中对 rac-8DLMe 聚合而不是 7-HL 的强烈动力学偏好导致了二嵌段共聚物 P3HB-b-P7HHp 的形成，显示出两个结晶域，Tm1~ 65 °C 和 Tm2~ 160 °C。通过调整共聚条件也获得了Tm高达164℃的半结晶无规共聚物。力学测试表明，P3HB-b-P7HHp 可以协同地将全同立构 P3HB 的高模量与 P7HHp 的高延展性结合起来。
Ring‐opening polymerization (ROP) of lactones or cyclic (di)esters is a powerful method to produce well‐defined, high‐molecular‐weight (bio)degradable aliphatic polyesters. While the ROP of lactones of various ring sizes has been extensively studied, the ROP of the simplest eight‐membered lactone, 7‐heptanolactone (7‐HL), has not been reported using metal‐based catalysts. Accordingly, this contribution reports the ROP of 7‐HL via metal‐catalyzed coordinative‐insertion polymerization to the corresponding high‐molecular‐weight polyester, poly(7‐hydroxyheptanoate) (P7HHp). The resulting P7HHp is a semi‐crystalline material, with aTmof 68 °C, which is ~10 °C higher than poly(ε‐caprolactone) derived from the seven‐membered lactone. Mechanical testing showed that P7HHp is a hard and tough plastic, with elongation at break >670%. P7HHp‐based polyesters with higherTmvalues have been achieved through stereoselective copolymerization of 7‐HL with an eight‐membered cyclic diester, racemic dimethyl diolide (rac‐8DLMe), known to lead to highTmpoly(3‐hydroxyburtyrate) (P3HB). Notably, catalyst's strong kinetic preference for polymerizingrac‐8DLMeover 7‐HL in the 1/1 comonomer mixture rendered the formation of di‐block copolymer P3HB‐b‐P7HHp, showing two crystalline domains withTm1~ 65 °C andTm2~ 160 °C. Semi‐crystalline random copolymers withTmup to 164 °C have also been obtained by adjusting copolymerization conditions. Mechanical testing showed that P3HB‐b‐P7HHp can synergistically combine the high modulus of isotactic P3HB with the high ductility of P7HHp.