PDMS－PA多嵌段共聚物的超临界流体辅助熔融反应制备新技术研究

The synthesis and structure control of high-performance multi-block copolymers is one of the most important and intensively investigated areas of polymer science. In this project, the polydimethylsiloxane(PDMS) - polyamide(PA) multi-block copolymer, with a characteristic of thermoplastic elastomer, will be prepared in melt in two routes, the polymer-monomer condensation and the polymer-polymer condensation, based on a supercritical fluid aided polycondensation process. In comparison with the conventional solution process, the process adopted in this project is more environmentally benign since it is free of solvents. In addition, the application of the supercritical fluid will inhibit the phase separation behavior during the reaction process, enhance the mass transport in a highly viscous fluid without the need to increase the reaction temperature, and finally promotes the reaction as a result. Meanwhile, the use of the above two routes will enrich the means of the structure control of the products. Based on these technologies, it is feasible to controllably prepare PDMS-PA multi-block copolymers with different micro-chain structure, and demonstrate the internal relationship related to the preparation, the structure and the performance of those copolymers. All these issues are significant for the independent development of the PDMS/PA thermoplastic elastomer and also can provide a reference for the preparation of other multi-block copolymers which main chain are not completely composed of carbon element. There are several key issues should be solved in this project, including the effect of the dissolution and swelling of supercritical fluid on the rheological behavior of the reaction system, the inhibition of the phase separation behavior, and the enhancement of the mass transfer, as well as the microscopic structure control of the multi-block copolymers.

高性能多嵌段共聚物制备及结构调控是高分子科学领域的重要研究内容。本项目拟借助超临界流体技术，采用聚合物－单体缩合及聚合物－聚合物缩合两条路线，实现具有热塑性弹性体特征的聚二甲基硅氧烷（PDMS）－聚酰胺（PA）多嵌段共聚物的熔融缩聚制备。与传统溶液过程相比，熔融缩聚由于不使用溶剂而更加绿色环保。超临界流体的引入，可抑制反应过程中的相分离行为，降低该反应过程的温度，强化高粘条件下的传质，促进反应进行。两条制备路线的采用，则进一步丰富了产物结构的调控手段。利用上述技术，可控地制备出一系列不同微观链结构的PDMS－PA多嵌段共聚物，可望深入研究其"过程－结构－性能"关系，为PDMS/PA热塑性弹性体自主开发建立基础，也为其它非全碳主链多嵌段共聚物制备提供借鉴。拟解决的问题主要有：超临界流体对反应体系的溶解、溶胀及流变行为与其对反应过程中相分离抑制与传质强化效果的耦合作用；以及产物微观结构的调控。

高性能多嵌段共聚物制备及结构调控是高分子科学领域的重要研究内容。本项目拟借助超临界流体技术，实现具有热塑性弹性体特征的聚二甲基硅氧烷（PDMS）－聚酰胺（PA）多嵌段共聚物的熔融缩聚制备。本项目以端氨基聚二甲基硅氧烷（PDMS-NH2）、端异氰酸酯基聚二甲基硅氧烷（PDMS-NCO）和端羧基聚酰胺6（PA6-COOH）为起始原料，主要研究了PDMS－PA多嵌段共聚物的超临界流体辅助熔融缩聚、PDMS-PA多嵌段共聚物的结构性能关系以及PDMS-PA多嵌段共聚物对PDMS/PA6聚合物共混体系的增溶作用。研究结果表明，无论是借助氨基与羧基的缩合反应，还是活性更高的异氰酸基与羧基的缩合反应，本体聚合均仅能制备PDMS质量分数小于30%的PDMS－PA6多嵌段共聚物。PDMS质量分数超过30%时，产物会出现宏观相分离，无法得到具有足够机械强度的产物。而超临界流体的引入的确可以促进PDMS-NCO与PA6-COOH的本体共缩聚，所制共聚物链长有一定的提高。PDMS-PA多嵌段共聚物呈现出明显的微相分离特征，具有一定弹性，并反映出明显的物理交联特征。PDMS-PA多嵌段共聚物可用作PDMS和PA的共混相容剂，有效提高两者的界面相容性，减小分散相的颗粒尺寸。总体上说，本项目实现了基于溶液或熔融缩聚过程的 PDMS－PA 多嵌段共聚物制备；证实了超临界流体的存在对PDMS/PA缩聚反应具有一定的过程强化作用，探讨了PDMS－PA 多嵌段共聚物的制备条件与其结构性能间的相互关系及其作为相容剂的应用可能。