with two moles of a suitable hydroxy extended alkyl acrylate to form the corresponding isocyanate capped acrylate suitable diisocyanates for use in this step are aliphatic and cycloaliphatic diisocyanates e g dicyclohexylmethylene diisocyanate isophorone diisocyanate hexamethylene diisocyanates and trimethylhexamethylene diisocyanate the hydroxy extended alkyl acrylate monomer reactant may be selected from reaction products of such hydroxyalkyl acrylate compounds as hydroxymethyl acrylate hydroxyethyl acrylate hydroxypropyl acrylate hydroxybutyl acrylate and the like with a suitable alkyl chain extender such as a caprolactone caprolactam an epoxide and the like a preferred reaction product is available commercially as 34 tone m 100 34 from union carbide corp which is caprolactone acrylate monomer for purposes of this invention the term 34 acrylate 34 includes the corresponding 34 methacrylate 34 derivative in this step one mole of a simple alkylene polyol compound is added to the intermediate of the first step to hydroxyalkylene encap the remaining end of the diisocyanate suitable alkylene polyols have 3 6 hydroxyl groups and 3 6 carbon atoms prefaced compounds are glycerol trimethylolpropane 1 2 6 hexanetriol pentaerythritol l arabinose dipentaerythritol and sorbitol glycerol is most preferred in the final step of the synthesis of the urethane acrylate compound of the invention at least one half mole of a dicarboxylic acid or anhydride is added.