. . . . " 1 to 6 carbon atoms, X is a functional group capable of free-radical transformation selected from the group consisting of an acrylate, a methacrylate, an allyl ether, a vinyl ether, vinylbenzyl, a vinylsulfonic ester, Z is H, CmH2m+1, phosphate, the same as X, m is 1 to 8, and n varies in order to achieve said molecular weight;" .