Photoinduced shape fixity and thermal-induced shape recovery properties based on polyvinyl alcohol bearing coumarin

In this paper, polyvinyl alcohol (PVA) bearing coumarin with different degrees of substitution (DS) are synthesized by esterifying hydroxyl of PVA with 7-carboxylmethoxycoumarin. The grafted polymer has photosensitive property and presents photocrosslinking due to the photodimerization between pendant coumarin groups, which affords PVA-coumarin sample photoinduced shape fixity properties. PVA-coumarin can be cross-linked after being illuminated under UV light of 360 nm; this provides the possibility that the sample has shape memory properties only if the cross-linking extent is suitable. The shape memory properties were induced by thermal as most shape memory polymer do. In fact, the shape fixity and recovery has strong relationship with DS, irradiation time, and thickness of sample. The effect of DS on the grafted polymer structure and properties has been studied by differential scanning calorimetry, thermogravimetric analysis, and UV spectra.