Kinetic investigation of photopolymerization initiated by oligomeric photolatent base

Macrophotoinitiators often show polymer effect and photolatent bases make molecular amplification reaction. A main-chain oligomer containing α-aminoalkylphenone chromophore (OAK) had been synthesized with the characteristics of both photoinitiators and photolatent base hybrid structure. In order to determine whether such an effect or reaction exists in photopolymerization initiated by OAK, we used photo-differential scanning calorimeter to analyze the kinetic behavior. The experimental rate constants at different conversions were obtained by Arrhenius equation at different temperatures, the theoretic rate constants were simultaneously calculated with the use of phenomenological model. The results showed that the model correctly predicts the rate constant at the early stage, but underestimates it later. The comparative experiment between OAK and polymeric α-hydroxyalkylphenone photoinitiator (KIP150) shows that the molecular proliferation reaction caused by OAK significantly increases the experimental rate constant in the high-crosslinked stages of the polymerization. The photolatent base would be expected to provide one possible pathway in tackling photo-curing of opaque/thick material.