A novel polymeric type II photoinitiator, namely poly(ethylene oxide) dimethylammonium thioxanthonemethyl-carboxylate (PEO-NH+(Me)(2) TX-CH2COO-), possessing both photochromophoric and hydrogen donating groups in the structure was synthesized and characterized. In contrast to existing type II photoinitiators, the present photoinitiator initiates free radical polymerization by counteranion anion excitation even in the absence of added hydrogen donors. The photoinitiator can be applied to the polymerization of monomers soluble in organic solvents or water.