Two different reaction mechanisms of cinnamate side groups attached to the various polymer backbones

Cinnamate polymers are well known photoreactive polymers due to 2+2] cycloaddition reaction of cinnamate side group. In this work, we have found that the cinnamate side groups could be also reacted by thermal energy, and this reaction is presumed to attribute to the radical reaction of carbon double bond in the cinnamate groups. Contrary to the photocycloaddition reaction of the cinnamate side groups, the thermal reaction of cinnamate side group was closely related to the flexibility of polymer backbone. The difference of the mechanism between the photocycloaddition reaction and thermal crosslinking reaction was confirmed by ¹H NMR and ¹³C NMR analysis of the model compound.