Water‐Soluble Imide‐amide Copolymers. II. Preparation and Characterization of Poly (acrylamide‐co‐p‐maleimidobenzoic Acid)

AbstractThe comonomer required, p‐maleimidobenzoic acid (MBA) was first prepared in good yield by refinements of published methods. p‐Carboxysuccinanilic acid (CSA), and p‐succinimidobenzoic acid (SBA), were also prepared to provide models useful for IR and NMR for spectroscopic assignments of the new copolymers. Polymerization of MBA with acrylamide in glacial acetic acid at 60°C gave copolymers with estimated viscosity average molecular weights of 60,000 to 90,000. Yields and viscosity average molecular weights decreased as the MBA to acrylamide monomer feed ratio was increased. The rate of incorporation of MBA into the copolymer rose from 7 to 23% when the mole ratio in the feed was raised from 5 to 20%. Decreasing the initiator concentration increased molecular weights by less than predicted and reduced the yield of copolymer for any given feed ratio of MBA to acrylamide. In all cases about 30–40% of the MBA units in the purified copolymers were hydrolyzed. A change to dimethyl sulfoxide solvent gave good, and poor yields of copolymer at 5 and 10 mol % MBA, respectively, and no copolymer at 20 mol % MBA. Viscosity average molecular weights of the copolymer products prepared in DMSO were somewhat lower than obtained for the copolymers prepared in acetic acid. Polymerization in a DMSO‐water mixture gave a negligible yield of polymeric product. Instead, only hydrolysates of MBA precipitated when the coloured polymerization solutions were added to methanol.