endently a hydrogen atom, a lower alkyl group preferably having 1to 6 carbon atoms or a cyano group; R is --(CH.sub.2)q--, --COO(CH.sub.2).sub.q -- or --CONH(CH.sub.2).sub.q --; q is an integer of 1 to 6; and p is an integer of 1 to 6.DESCRIPTION OF THE PREFERRED EMBODIMENTSAs the compound (A) having an azo group in the molecule and having a reactive functional group at each end of the molecule wh