Photodimerization of Coumarin Functionalized Poly(alkyl Acrylate) and Poly(alkyl Methacrylate) Random Copolymers: Influence of Copolymer Composition on Photocrosslinking

Coumarin‐containing poly(alkyl (meth)acrylates) were prepared via 70–80% esterification of hydroxy‐containing acrylic copolymers, then solution cast into thin films and photocrosslinked via the dimerization of coumarin derivatives with UVA light. The coumarin‐modified polymers crosslinked upon exposure and exhibited gel fractions between 74 and 99%. Coumarin dimerization efficiency increased with higher polymer mobility at the irradiation temperature. The effects of light intensity and irradiation time in photo‐dimerized systems followed the Bunsen‐Roscoe reciprocity law indicating that coumarin photodimerization depended only on dose. Thus, low intensities are overcome with longer times. This is an important advantage over photoinitiated free radical crosslinking which depends on irradiation intensity to the ½ power.