Aqueous macromolecular photoinitiator and preparation method thereof

The invention relates to an aqueous macromolecular photoinitiator and a preparation method thereof. The general formula of the aqueous macromolecular photoinitiator is (i). The aqueous macromolecular photoinitiator prepared by the method has the photoinitiating efficiency equivalent to a corresponding micro-molecular photoinitiator and has better compatibility with an aqueous light-cured resin; carboxylate ions and sulfosalt ions exist in a molecular chain simultaneously, so the resin has better water solubility than an aqueous macromolecular photoinitiator only containing carboxylate ions; and in addition, the price of an introduced chain extender (4-aminobenzenesulfonic acid) used for sulfonic acid group is lower than that of a conventional aqueous functional monomer (dihydromethylpropionic acid), so that the cost of products is reduced and the industrial production is facilitated. At the same time, in the method, the chain is extended by using the functional monomer with photoinitiating function, so the content of photoinitiating radicals in the resin per gram is improved and the aqueous macromolecular photoinitiator has better photoinitiating efficiency than the aqueous macromolecular photoinitiator taking end radicals as the photoinitiating radicals.