Development of Novel Biodegradable Aliphatic Polyesters Prepared by Catalysts Containing Metals

聚(L-乳酸)，即聚(L-丙交酯)[聚(L-乳酸)]具有良好的生物相容性和力学性能。然而，聚(L-LA)的主要问题是脆性和生物降解性低。因此，在这项工作中，为了改善聚(L-LA)的这些缺点，同时保持其优点，我们制备了新型的可生物降解的脂肪族聚酯。通过引入去脂肽(DP)单元改善了聚(L-LA)的生物降解性；通过共聚DP单体(DPS是由各种氨基和羟基酸衍生物合成的DPS)大大改善了聚L-LA的酶降解性能。此外，研究还发现，以氨基酸L异构体为原料制备的DP单体的生物降解性改善效果最好。改善了聚(L-LA)链的脆性；已内酯(CL)或其衍生物(4-烷基己内酯)单元引入到聚(L-LA)链中，使其脆性得到较大改善。这使得我们能够调节共聚物的降解性。上述结果使我们能够制备DP/CL/L-LA三元共聚物。从生物降解性和性能的平衡来看，组成比约为5/20/75的三元共聚物是最好的聚合物，对于生物可降解聚合物的许多应用来说，这些聚合物的官能化是非常重要的。因此，我们制备了具有不同基团的L-LA共聚物。例如，含羟基的CL/L-LA共聚物与聚(L-LA)相比具有很高的生物降解性。此外，我们还通过将聚合物的反应性双键转化为多官能团(双键/环氧/二醇)，合成了具有多官能团(双键/环氧/二醇)的共聚物。最后，我们通过对这些基团进行化学修饰，成功地开发出了交联水凝胶聚合物。

Poly (L-1actic acid), namely poly (L-lactide) [poly (L-LA)] has such advantages as good biocompatibility and mechanical properties. However, the major problems of poly (L-LA) are its brittleness and low biodegradability. Therefore, in this work, to improve these disadvantages of poly (L-LA), but keeping its advantages, we have prepared novel biodegradable aliphatic polyesters. The following significant results were obtainedImprovement of biodegradability of poly (L-LA) by introducing depsipetide (DP) units ; The enzymatic degradation of poly (L-LA) was much improved by copolymerizing DP monomer (DPs were synthsized from various amino asids and hydoxy acid derivatives). Furthermore, it was found that the biodegradability was most improved by using DP monmers prepared from L-isomers of amino asids.Improvement of brittleness of poly (L-LA) chains ; The introduction of caprolactone (CL) or its derivative (4-alkylated caprolactone) units into poly (L-LA) chains resulted in a greater improvement of the brittleness of poly (L-LA). And this enabled us to regulate the degradability of copolymers.The above results rendered us to prepare DP/CL/L-LA terpolymers. The terpolymer with composition ratio about 5/20/75 was found to be the best polymer judging by the balance of biodegradability and properties.For many applications of biodegradable polymers, functionalizations of these polymers are very important. We have therefore prepared L-LA copolymers having various **nctinal groups. For example, CL/L-LA copolymers with hydroxy group was found to be highly biodegradable compared with poly (L-LA). Further, we have synthesized the copolymers with multifunctional groups (double bond/epoxy/diol) by transforming the reactive double bond of polymers into these functional groups. Finally, we have succeeded in developing cross-linked hydrogel polymers by chemical modification of these groups.