Photobase generators: Recent progress and application trend in polymer systems

Recent progress in photochemical generation of organic bases and its applications to polymer science and technologies are reviewed. Although photobase generators (PBGs) have been desired as a novel photolatent catalyst, fewer examples are known compared to photoradical and photoacid generators. In this decade, several PBGs such as carbamates, O-acyloximes, and ammonium salts have been improved in thermal stability, solubility, multi-functionality, and photo-sensitivity. In addition, new molecular designs including amineimides, α-aminoketones, some amidine precursors, and aromatic ureas have been proposed as novel PBGs. New applications of these PBGs have been developed in photo-induced polymerization, depolymerization, crosslinking, and de-crosslinking as well as photo-imaging.