Ring formation on heating poly(methyl vinyl ether-alt-ammonium maleamate)

Poly(methyl vinyl ether-alt-ammonium maleamate), when heated at up to 100°C while removing volatiles, is converted to polymer whose infrared, elemental analysis and T_g are consistent with a structure predominantly that of poly(methyl vinyl ether-alt-maleic anhydride). Maleimide comonomer units are a substantially lesser component. Evidence is presented that a part of the reaction sequence may involve hydrolysis of imide or amide.