Progress in cationic photopolymerization

 
The invention of a new aluminum based photo acid generator PAG, salts that are used to initiate cationic photopolymerization, is a huge achievement. Classical anions for PAGs are fluorides of antimony, arsenic, phosphor, or boron. These suffer from toxicity and hydrolysis sensitivity. The also used borates on the other hand are problematic because of their expensive synthetic route. The new aluminum based PAG replaces not only the highly toxic and/or expensive PAGs, but also shows a significantly higher reactivity (even for usually low reactive glycidyl-based monomers). This performance opens the floor for new applications of cationic photopolymerization. With the development of Radical Induced Cationic Frontal Polymerization (RICFP) also bubble free bulk curing of epoxy resins within minutes without oven or spacial limitations by using the liberated reaction heat becomes possible.