Complex-radical copolymerization of N-vinyl pyrrolidone with isostructural analogs of maleic anhydride

Radical copolymerizations of N-vinyl-2-pyrrolidone (VP) with isostructural analogs of maleic anhydride (MA), such as citraconic anhydride (CA) and N-substituted maleimides [maleimide (MI), N-ethylmaleimide (EMI) and N-phenylmaleimide (PhMI)] were studied. Compositions of copolymers synthesized in a wide range of monomer feed ratios were determined by alkali titration (for anhydride copolymers), FTIR and H-1 NMR spectroscopy using 1495 and 630 cm(-1) (for VP-MI), 1289 and 1225 cm(-1) (for VP-EMI) and 1050 and 3067 cm(-1) (for VP-PhMI) analytical bands and integral areas of CH2 (pyrrolidone ring) and CH (MI), CH3 (EMI) and CH= (benzene ring in PhMI) groups, respectively. Electron-donor VP monomer was found to have substantially different reactivities in the radical copolymerization with MA, CA and N-substituted (H, C2H5 and phenyl) malemides as electron-acceptor comonomers. Effects of H-bonding and N -> O=C coordination on the monomer reactivity ratios were evaluated. Tendency to alternation of the monomer pairs increases in the order of VP-MA > VP-CA > VP-MI > VP-PhMI > VP-EMI. Structure-thermal property-relationship for the synthesized copolymers was also studied.