crylates and methacrylates such as 2-hydroxyethyl acrylate, 3-hydoxypropyl acrylate, 2-hydroxyethyl methacrylate and 3-hydroxypropyl methacrylate; vinyl macromers consisting of vinyl polymers having a polymerizable functional group at one end; polyester macromers consisting of polyesters having a polymerizable functional group at one end; polyurethane macromers consisting of polyurethanes having a