可循环加工热固性聚丙交酯的反应挤出研究

Polylactide has broad application in the field of tissue engineering, drug delivery and package due to its good biocompatibility, biodegradability and high modulus properties. However, it is a problem to synthesize high molecular weight and modulus polylactide, cross-linking reaction is a good way to solve this problem. Reactive extrusion is a process that integrates the polymer synthesizing and processing to one and the high shearing makes it possible to synthesize high molecular weight cross-linked polymers. In the same time, reactive extrusion process has the advantage of saving energy and resources, and has little side effects on the environment. Unreprocessability is the major disadvantage during the usage of the cross-linked thermoset polymers and we will prepare cross-linked thermoset polylactide directly through the organic guanidine catalyzed ring-opening polymerization and cross-linked reaction with reactive extrusion processing in this project. The organic guanidine could also catalyze the internal trans-esterification reaction of the thermoset polylactide under certain temperature, which makes the reversible dynamic bond transfer achievably. Thus, the high modulus cross-linked thermoset polylactide could be reprocessed at a certain temperature and pressure. We will study the ring opening polymerization kinetics and cross-linked reaction kinetics during the reactive extrusion process and establish relevant reactive extrusion process parameters and develop high performance thermoset polylactide.

聚丙交酯具有良好的生物相容性、可降解性和高模量,在组织工程、药物释放、包装等领域具有广泛的应用前景,然而制备高分子量和高模量的聚丙交酯则是一个难题，适度微交联反应是解决这个问题的可行方法。反应性挤出加工将高分子合成和加工两个过程融为一体，加工过程的高剪切力使制备高分子量交联聚合物成为可能，反应加工同时具有节约能源和资源、对环境带来的负面效应小等优点。然而热固性交联聚合物的不可再加工性则是其使用过程中的一个主要缺点，本项目利用反应性挤出加工，通过有机双胍催化的开环聚合和交联反应，直接制备热固性交联聚丙交酯。有机双胍同时也可以催化热固性聚丙交酯的分子间酯交换反应，实现热固性聚丙交酯的动态可逆化学键转变，从而在一定温度、压力下实现高模量热固性聚丙交酯的循环再加工。我们将研究反应加工过程中的开环聚合动力学、交联反应动力学,确立相关反应挤出加工参数，通过反应挤出直接制备高性能热固性可再加工聚丙交酯。

目前用于开环聚合的催化剂，都存在着难以回收循环使用以及从聚合物中分离困难的问题。本项目中，我们拟将可催化开环聚合的亚氨基-三(二甲氨基)正膦(HMP1)接枝到六氯环三聚磷腈(HCCP)和4,4’-二羟基二苯砜(BPS)包覆的磁性纳米粒子表面，将磁性纳米粒子易分离的特点与基于HMP1的催化剂可以高效催化开环聚合的特性相结合，制备可循环使用的开环聚合催化剂。预期合成的催化剂可开环聚合环状内酯、环状碳酸酯和环醚等环状单体以及其共聚。通过研究有机催化剂接枝到磁性纳米粒子的制备过程，确定制备可开环聚合磁性纳米粒子负载有机催化剂的关键因素；通过研究开环聚反应动力学、催化机理、外消旋化丙交酯的立构规整性聚合以及催化剂的可循环使用性，揭示催化剂性能与结构、组成的关系。在此基础上，设计合成生物相容、可循环使用的开环聚合催化剂，建立新型开环聚合催化体系，丰富生物降解聚合物制备方法。