Abstract：
Isoporous membranes produced from diblock copolymers commonly display a poor mechanical property that shows many negative impacts on their separation application. It is theoretically predicted that dense films produced from symmetric triblock copolymers show much stronger mechanical properties than those of homologous diblock copolymers. However, to the best of our knowledge, symmetric triblock copolymers have rarely been fabricated into isoporous membranes before, and a full understanding of separation as well as mechanical properties of membranes prepared from triblock copolymers and homologous diblock copolymers has not been conducted, either. In this work, a cleavable symmetric triblock copolymer with polystyrene as the side block and poly(4-vinylpyridine) (P4VP) as the middle block was synthesized and designed by the RAFT polymerization using the symmetric chain transfer agent, which located at the center of polymer chains and could be removed to produce homologous diblock copolymers with half-length while having the same composition as that found in triblock copolymers. The self-assembly of these two copolymers in thin films and casting solutions was first investigated, observing that they displayed similar self-organized structures under these two conditions. When fabricated into isoporous membranes, they showed similar pore sizes (5-7% difference) and comparable rejection performance (∼10% difference). However, isoporous membranes produced from triblock copolymers showed significantly improved mechanical strength and higher toughness (2-10 times larger) as evidenced by the compacting resistance, strain-stress determination, and nanoindentation testing, suggesting the unique and novel structure-performance relationship in the isoporous membranes produced from symmetric triblock copolymers. The above finding will guide the way to fabricate mechanically robust isoporous membranes without notably changing the separation performance from rarely used symmetric triblock copolymers, which can be synthesized by the controlled polymerization as facilely as that found for diblock copolymers.
摘要：
由二嵌段共聚物生产的多孔膜通常表现出较差的机械性能,这对它们的分离应用显示出许多负面影响。从理论上预测，由对称三嵌段共聚物生产的致密膜显示出比同源二嵌段共聚物更强的机械性能。然而,据我们所知,对称三嵌段共聚物以前很少被制造成多孔膜，并且尚未对由三嵌段共聚物和同源二嵌段共聚物制备的膜的分离以及机械性能进行充分了解，要么。在这项工作中,利用对称链转移剂,通过RAFT聚合,合成并设计了以聚苯乙烯为侧嵌段,聚(4-乙烯基吡啶)(P4VP)为中间嵌段的可裂解对称三嵌段共聚物,它位于聚合物链的中心，可以被去除以产生具有半长的同源二嵌段共聚物，同时具有与三嵌段共聚物相同的组成。首先研究了这两种共聚物在薄膜和流延溶液中的自组装，观察到它们在这两种条件下表现出相似的自组织结构。当被制成等孔膜时，它们显示出相似的孔径(5-7%的差异)和相当的排斥性能(~10%的差异)。然而,由三嵌段共聚物生产的多孔膜显示出显着改善的机械强度和更高的韧性（2-10倍大），如通过压缩阻力证明，应变-应力测定,和纳米压痕测试，表明由对称三嵌段共聚物产生的均孔膜中独特而新颖的结构-性能关系。上述发现将指导制造机械坚固的均孔膜的方法，而不会显着改变很少使用的对称三嵌段共聚物的分离性能。它可以通过控制聚合合成，就像对二嵌段共聚物发现的那样容易。
