UV light induced plasticization and light activated shape memory of spiropyran doped ethylene-vinyl acetate copolymers

Abstract

Light activated shape memory polymers (LASMPs) are relatively new kinds of smart materials and have significant technological applications ranging from biomedical devices to aerospace technology. EVA films doped with spiropyran with contents ranging from 0.1% to 3% show efficient UV activated shape memory behaviors if the fixed shape deformation is limited within 80%. For EVA films containing 3% spiropyran, UV irradiation causes a decrease in EVA modulus of about 44%. FT-IR and solid ¹³C NMR in association with UV-vis absorption analysis demonstrate that UV irradiation transforms spiropyran from the SP form to the MC form, meanwhile, it induces an increase in the molecular mobility in the amorphous phase of EVA. Thus, the spiropyran-doped EVA films act as LASMPs via a mechanism of light induced plasticization. Light activated spiropyran acts as a plasticizer to EVA.