. "tructure (II): wherein R is an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a phenyl group, R??? is hydrogen or an alkyl having 1 to 4 carbon atoms, and X is ???O??? or ???NH???, in an amount of from about 20 to about 70 weight %, recurring units are derived from one or more (meth)acrylonitriles, cyanostyrenes, and cyanoacrylates,in an amount of from abou" . . .