col and said second moiety being selected from the group consisting or glycine anhydride; alloxan; uracil; 5,6-dihydrouracil; glycolic acid; lactic acid; and lactones; and said second component comprises from about 20 wt. % to about 70 wt. %, based upon the weight of said copolymer, of units having the formula: --OEO--CO--R--CO--, wherein E is an organic radical selected from the group consisting