Thioxanthone based water-soluble photoinitiators for acrylamide photopolymerization

The two water-soluble thioxanthone-based 2-(carboxymethoxy) thioxanthone, 1A and 2-thioxanthone-thioacetic acid sodium salts, 2A were synthesized and characterized by spectroscopic methods. The quantum yield for fluorescence emission (φf) in water was found to be 0.50 for 1A and 0.05 for 2A. The long phosphorescence lifetime, that is 201 and 114 ms in a matrix at 77 K for 1A and 2A, respectively, indicates a π–π∗ nature of the lowest triplet state. The triplet lifetimes were determined by laser flash photolysis as 12 and 12.6 μs for 1A and 2A. Polymerization of acrylamide (AAm) was initiated by both initiators in water. Decarboxylation of initiators was achieved during 20 min of irradiation. It was found that 2A initiated polymerization of AAm in water more efficiently than 1A.