Study on photobase generation from α-aminoketones: Photocrosslinking of epoxides with carboxylic acids

Abstract

It was demonstrated that α-aminoketones work effectively as photobase generators in epoxy-based compositions. After irradiation they accelerate the thermal crosslinking reaction of phenol novolac epoxy resin with polyacrylate having carboxylic acid groups despite of their high latency before irradiated. The acceleration effect depends on the structure of the photogenerated amines. Conformational calculations of the α-aminoketones and the related compounds suggest that folded conformations contribute to the latency of the amine moiety. In the conformations, the bulky benzoyl group of the aminoketone shields the amino nitrogen from acidic species present in the composition. By irradiation, the benzoyl part is cleaved and the active tertiary amine base with small substituents is eventually liberated. The investigation using model amines supported the explanation. The compositions used for this study can be utilized in the base-catalyzed imaging applications.