Synthesis and properties of photosensitive rubbers. III. Synthesis of chloroacetylated polybutadiene and its photosensitivity

Polymers having chloroacetate groups were prepared by addition reaction of various chloroacetic acids, such as mono‐, di‐, and trichloroacetic acids, to cis‐1,4‐polybutadiene under nitrogen atmosphere for obtaining photosensitive rubbers. The structure of products obtained was identified as a cyclized polybutadiene having pendent chloroacetate groups. The amount of the incorporated substituent increased up to the maximum of around 20 mol %, and the amount of the residual unsaturated groups in the polymer backbone decreased due to the cyclization of the double bond. Chloroacetylated polybutadiene had higher photocrosslinkability by UV irradiation than chloroacetylated polybutadiene had higher photocrosslinkability by UV irradiation than chloroacetylated chitosan or PVA owing to the high reactivity of the chloroacetate groups and the double bonds in the polymer. The photosensitivity depends both on the amount of the incorporated chloroacetate groups and the residual double bonds in the polymer and also depends on the glass transition temperature (Tg) of the polymer, and the dependence of the crosslinking reaction on Tg was interpreted to be due to diffusion controlled reaction between excited dichloroacetate groups and olefinic groups in the polymer.