开环聚合条件对聚乙交酯热稳定性的影响

Regulating thermal stability of PGA via adjusting ring opening polymerization conditions

采用金属化合物催化剂/羟基引发剂体系引发乙交酯开环聚合,制备了高相对分子质量聚乙交酯(PGA),研究了反应温度、反应时间、催化剂用量、单体与催化剂纯度、PGA的特性黏度,以及不同金属中心(如Sn,Al,Zn,Zr)和配体结构(如烷氧基、羧基、乙酰丙酮基和卤素)的催化剂对PGA热稳定性的影响规律。结果表明:在催化剂用量低于100μg/g的情况下,严格控制单体和催化剂纯度可使PGA的特性黏度显著提高,热降解温度提高了20.0~50.0℃;采用Sn基催化剂制备的PGA的热降解温度最低,采用Zn基和Al基催化剂制备的PGA的热降解温度最高可达318.6℃;金属化合物催化剂是控制PGA热稳定性的关键因素。

High molecular mass polyglycolic acid(PGA)was obtained from glycolide ring-opening polymerization reaction with metal compound catalyst and hydroxy initiator.The effects of reaction temperature and duration,catalyst usage,purity of monomer and catalyst,intrinsic viscosity of PGA,and catalysts which contain various metal centers(Sn,Al,Zn and Zr)and various types of ligands(alkoxy,carboxylate,acetylacetonate and halogen)on thermal stability of PGA were investigated.The results show that the intrinsic viscosity of PGA can be substantially enhanced by thoroughly purifying the monomer and the catalyst when a low level of catalyst of less than 100μg/g is utilized,leading to an increase in degradation temperature by 20.0 to 50.0℃.PGA prepared with Sn-based catalysts exhibits lowest thermal degradation temperature,while that of PGA made from Zn and Al-based catalysts reaches as high as 318.6℃.Metal compound catalysts used for PGA synthesis plays a critical role in controlling thermal stability of the polymer.