Development of shape memory polyurethane based on polyethylene glycol and liquefied 4,4′-diphenylmethane diisocyanate using a bulk method for biomedical applications

In this study, a series of shape memory polyurethanes (SMPUs) were synthesized successfully by the bulk polymerization method from liquefied 4,4′-diphenylmethane diisocyanate (L-MDI), 1,4-butanediol (BDO) and polyethylene glycol (PEG). The influence of the hard segment content (HSC) on the structure, morphology, properties and biocompatibility of PEG based SMPUs (PEGSMPUs) was carefully investigated. The results show that a microphase separation structure composed of a semicrystalline soft phase and an amorphous hard phase is formed in the PEG6000/L-MDI/BDO system. Crystallization of the PEG soft segment is influenced by the hard segments. The PEG semicrystalline soft phase serves as a reversible phase while the L-MDI−BDO hard segment acts as physical netpoints. Finally, a cyclic tensile test shows that all PEGSMPUs have good shape recovery (e.g. above 80%), whereas good shape fixity can only be achieved when the HSC is less than 35 wt%. The Cell Counting Kit 8 assay also demonstrates that only PEGSMPUs containing less than 40 wt% HSC have low cytotoxicity. It is thus concluded that PEGSMPUs bearing both good shape memory effects and good biocompatibility can be used as shape memory materials for biomedical applications when the HSC is less than 35 wt%. © 2014 Society of Chemical Industry