Abstract Uranyl nitrate, acetate, sulfate, and dibutyl phosphate were used in solution for the photoinitiation of homopolymerization and copolymerization of hydroxypropyl acrylate and tetraethylene glycol dimethacrylate. Solvents used included water, water‐ethylene glycol mixtures, and dimethylformamide. Polymer yields in excess of 90% can readily be obtained by exposing solutions containing 0.014M UO22+ to light from a tungsten bulb for 1 hr. The rigidity of the polymers varied directly, the affinity for water in‐versely, with the concentration of tetraethylene glycol dimethacrylate in the monomer mixture. Poly(hydroxypropy1 acrylate) contained 52% water and poly(tetraethy1ene glycol dimethacrylate) 34% water, a t equilibrium.