This invention relates to copolymerizable ultraviolet light absorber monomers which are .alpha.,.beta.-unsaturated dicarboxylic half-esters of 2-hydroxy,alkoxy,methylolbenzophenone intermediate compounds. The monomers have the formula: ##STR1## where R is alkyl C.sub.1 -C.sub.8, and n is 1 or 2, andY is a half-acyl radical of a .alpha.,.beta.-unsaturated dicarboxylic acid selected from the group of maleic and itaconic acids.The monomers herein are made by monoesterifying intermediate compounds, prepared by converting a 2-hydroxy,alkoxy,benzophenone to the corresponding methylol derivative by a formylation reaction, with the anhydride of the desired acid.In the preferred embodiments of the invention, the alkoxy group is methoxy in the 4-position, the methylol group which is half-esterified is a monomethylol group located at the 3- or 5- position of the phenyl ring containing the hydroxy group, and the acid anhydride is maleic anhydride.Copolymerization of the monomers herein with vinyl monomers provide improved ultraviolet light stable copolymers for industrial and commercial applications.