The water soluble copolymers of the invention have the structure: ##STR3## wherein E is the repeat unit remaining after polymerization of an alpha, beta ethylenically unsaturated compound, R1 is H or lower (C1 -C4) alkyl, ##STR4## or a mixture of both, n is an integer of from about 1 to about 40, R3 is hydrogen, lower (C1 -C4) alkyl, or an acetate formed as a cap on the polyethyleneglycol methacry