Biocompound-Based Multiple Shape Memory Polymers Reinforced by Photo-Cross-Linking.

For the design of shape memory polymers with potential biomedical applications, we synthesized methacrylate-based monomers bearing biological compounds such as cholic acid and cinnamic acid in addition to oligo(ethylene glycol) as pendant groups and opted to use a simple radical polymerization method for the preparation of the copolymers. The glass transition temperatures of these polymers are broad and tunable and can thus accommodate dual and triple shape memory behaviors. The fixity ratios of dual and triple shape memory are all above 91%. The recovery ratio of dual shape memory is 89.5%, whereas the two recovery ratios of triple shape memory are 53.2 and 81.5%, respectively. To further improve the shape memory properties, a cinnamic acid-based methacrylate monomer was incorporated into the copolymers to enable a photo-cross-linking of the terpolymer. After irradiation, the fixity ratios remain high, whereas the recovery ratios of dual and triple shape memories are much improved. The terpolymers after light irradiation even show quadruple shape memory property. Different irradiation times were tested to optimize the shape memory effects. The recovery ratio of dual shape memory of such terpolymers can reach as high as 98.6%, whereas the recovery ratios of triple and quadruple shape memories are improved to the range of 75.3-99.1%.