Halogenation of organic polymers having anhydride groups

Halogenated organic polymers, having pendant anhydride groups, of the formula MM(X)--CO--O--CO--R, where MM is a repeating chain segment of an organic polymer, X is one or more halogen groups attached to one or more carbons of said segment, and R is at least one moiety selected from the group consisting of hydrogen, substituted or unsubstituted organic groups and polymer groups,

• said halogenated organic polymers being prepared by halogenating a precursor organic polymer of the formula MM--CO--O--CO--R, where the MM segment comprises recurring copolymer groups of at least one non-halogen-containing olefin, vinyl, acrylate, or methacrylate monomer copolymerized with at least one non-halogen-containing alpha, beta-ethylenically unsaturated carboxylic acid monomer in which the resulting pendant --COOH groups on said copolymer have subsequently been converted to said anhydride groups.