wherein n is from 2 to about 200, preferably from about 5 to about 100, R1 is a divalent aliphatic hydrocarbon group, and X is an active hydrogen containing group such as ???SH, ???NOH, ???NHR, or ???O???(C2H4)(CH2CH2O2)a???H wherein R is hydrogen or an alkyl group and a is 0 to 100.