A systematic study of temperature-dependent cationic photopolymerization of cyclic esters

Abstract

The polymerization of cyclic esters to form polyesters is a thoroughly investigated topic and can be performed via anionic, cationic or metal-mediated techniques. While there have been attempts to apply light-induced on-demand initiation techniques, in most investigations photobase generators are used. In this work the focus lies on photoacid generators, which - contrary to many photobase generators - are easily stored, thermally stable, reactive, less sensitive towards water and oxygen inhibition and commercially available in various forms. However, in most cases the low reactivity of the monomers requires long polymerization times. Therefore, this study provides a basic study of the temperature-dependent cationic photopolymerization of cyclic esters and shows that polyesters can be formed in less than 5 min of irradiation at elevated temperatures and without solvents, leading to highly crystalline products. In addition, the temperature-dependent crystallinity, molecular weights and dispersities of the polymers are investigated and presented.