A novel thio-containing diamine with a benzophenone structure, 4-amino4'-[4-aminothiophenyl]benzophenone (AATBP), was synthesized. Two kinds of polymeric photoinitiators, PUPIA and PUPI, were synthesized through the polycondensation of toluene-2,4-diisocyanate with AATBP and/or N-methyldiethanolamine (MDEA). A macroamine, PUPA, was also synthesized for comparison. Fourier transform infrared, H-1 NMR, and gel permeation chromatography analyses confirmed the structures of all the polymers. The ultraviolet-visible spectra of PUPIA, PUPI, and AATBP were similar, and all exhibited the maximal absorption above 325 nm. The photopolymerization of two monomers with different functionalities, poly(propylene glycol)diacrylate and trimethylolpropane triacrylate initiated by PUPIA, PUPI/MDEA, PUPI/PUPA, AATBP/MDEA, and AATBP/PUPA, was studied through differential scanning photocalorimetry. The results showed that both PUPIA and PUPI/MDEA had high photoefficiency, and their low-molecular-weight counterparts could hardly initiate the photopolymerization. (c) 2006 Wiley Periodicals, Inc.