Polymers which are useful in the present invention include homopolymers such as polyisopropenyl ketone, polymethyl methacrylate, polyisopropyl vinyl ketone, poly-n-butyl acrylate, polyphenyl vinyl ketone and polyglycidyl methacrylate; and copolymers, such as a copolymer of isopropyl vinyl ketone and methyl vinyl ketone, and a copolymer of n-butyl methacrylate and methyl acrylate.