Photo-polymerization properties of type-II photoinitiator systems based on 2-chlorohexaaryl biimidazole (o-Cl-HABI) and various N-phenylglycine (NPG) derivatives

A series of p-substituted NPG derivatives (Cl-NPG, OMe-NPG and NO2-NPG) comprising different push–pull characteristics have been synthesized and characterized. The NPG derivatives have good thermal stability and red shifted absorption when compared with the original N-phenyl glycine (NPG) compound. These NPGs were selected in combination with 2-chlorohexaaryl biimidazole (o-Cl-HABI) for Type II free radical polymerization (FRP). Commercial NPG was also mixed with o-Cl-HABI for comparison. Their photo-polymerization properties were investigated by the gel fraction method in a nitrogen atmosphere. Electron transfer efficiencies for those Type II packages were studied by cyclic voltammetry (CV) and free energy change ΔG results.