I): CH2 ═CR1 CONR2 R3 (I) wherein R1 represents a hydrogen atom or a methyl group; R2 represents a hydrogen atom or a linear or branched Cn H2n+1 ; R3 represents a hydrogen atom, a linear or branched Cn H2n+1,N,N-dimethylaminopropyl group or --C(CH3)2 CH2 COCH3 ; and n is an integer in the range of 1 to 4, ii) a cyclic (meth)acrylamide compound represented by the general for