Pyridine type zwitterionic polyurethane with both multi-shape memory effect and moisture-sensitive shape memory effect for smart biomedical application

This paper reports a new type of zwitterionic polyurethane containing pyridine type zwitterionic segments for shape memory materials. The pyridine type zwitterionic shape memory polyurethanes (SMPUs) were synthesized using polyurethane polymerization from N,N-bis(2-hydroxylethethyl) isonicotinamide (BINA), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO), followed by a ring-opening reaction with 1,3-propanesultone (PS). The structure and properties of the pyridine-type zwitterionic SMPUs (PyZPUs) were investigated systematically. The results demonstrate that the PyZPUs form phase-separation structures composed of a hard phase and an amorphous soft phase with a broad glass transition. The shape memory tests show that the PyZPUs have thermal-induced dual-shape memory effects (SMEs), triple-SMEs and quadruple-SMEs and also moisture-sensitive SMEs. Comparatively, the samples with PS/BINA molar ratios of 0.6-0.8 have more than 86% shape recovery and more than 95% shape fixity with a heat stimulus. Under moisture conditions, these samples also show the quickest moisture-sensitive strain recovery, up to 86%. Moreover, the PyZPUs show good biocompatibility when the content of pyridine type zwitterionic segments is beyond 21 wt%. Thus, the PyZPUs are expected to have many promising applications in smart biomedical fields.