UV Light Induced Plasticization And Light Activated Shape Memory Of Spiropyran Doped Ethylene-vinyl Acetate Copolymers

In recent years, shape memory polymers (SMPs) have been developed fast and have been widely studied by scientists all over the world because of its potential applications in many fields. Besides traditional thermal responsive shape memory polymers, a variety of new shape memory polymer materials which can response to stimuli such as electricity, light and magnetic, have been prepared. Among them, light activated shape-memory polymers (LASMPs) have aroused great interest among research workers because of its advantages in remote controllability and operation at ambient conditions.In this paper we reported a new kind of LASMP by doping spiropyran into ethylene-vinyl acetate copolymer (EVA). The EVA films exhibited excellent shape memory effect under UV irradiation when deformation was less than80%. The mechanism of this phenomenon had been studied by different means such as nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (XRD), thermal mechanical analyzer (DMA), UV-vis absorption spectra (UV-Vis). The conclusions are list in the following:1) The modulus of EVA films decrease under UV irradiation, which showed a process of UV light induced plasticization. When spiropyran converts to its open MC form, it can decrease the interactions between EVA polymer chains and induce an increase in the molecular mobility in the amorphous phase of EVA, which makes deformed films recover to its initial shape.2) A new kind of LASMP was developed by taking advantage of UV light induced plasticization of EVA film with spiropyran. Deformation of this LASMP film should be less than80%to achieve good shape recovery effect. It should be mentioned that the shape recovery ratio of this film cannot be improved by chemical crosslinking.