Synergistic effects of zwitterionic segments and a silane coupling agent on zwitterionic shape memory polyurethanes

Recently, zwitterionic shape memory polyurethanes (ZSMPUs) have found many promising applications in smart biomedical field. This paper provides a novel strategy to improve shape memory properties of ZSMPUs by using a silane coupling agent, namely 3-glycidyloxypropyl-trimethoxysilane (KH560). The synergistic effects of zwitterionic segments and silane coupling agents on the structure, morphology, thermal properties, mechanical properties, and shape memory properties were carefully investigated. The results demonstrate that the incorporation of KH560 does not influence the original molecular structure and morphology of ZSMPUs, and the KH560-modified ZSMPUs form a hard–soft phase separation structure. Also, the KH560 modification promotes the entanglement of hard segments, and thus provides better mechanical properties to ZSMPUs-KH560. Moreover, the silane coupling agent can provide lubrication to influence the aggregation of soft segments while the zwitterionic segments promote the formation of crystal seeds. Therefore, a good semi-crystalline soft phase endows the ZSMPUs-KH560 with a decent shape fixity (e.g. above 94%), and the entangled hard segments greatly enhance the shape recovery of ZSMPUs (e.g. above 90%).