imethylamino)-styrene and p-methoxystyrene and wherein monomer (2) is an acrylic compound represented by the formula: wherein Y is SR, ZH, ZMe, NRR or a halogen atom, in which Z is an oxygen or sulfur atom, R is a hydrocarbon or halohydrocarbon radical having 1 to 20 carbon atoms, R and R each is hydrogen or a hydrocarbon radical having 1 to 20 carbon atoms including the case in which R and R a