Vinylpyrrolidone-N,N '-dimethylacrylamide water-soluble copolymers: synthesis, physical-chemical properties and proteic interactions

The radical copolymerization of N-vinyl-2-pyrrolidone (NVP) with N,N'-dimet hylacrylamide (DMAm) has been studied. The copolymer compositions were dete rmined from H-1-NMR. The radical reactivity ratios for DMAm (M-1) and VP (M -2) were found to be r(1) = 2.232 and r(2) = 0.186. An analysis of the wate r vapor absorption isotherms as a function of the lactam content in the cop olymer is reported. It was observed that the water vapor absorption decreas es with increasing VP content in the copolymer and show anomalous diffusion behavior with increasing temperature due to the coupling of diffusion and polymer relaxation mechanisms. From the water vapor sorption data the Arrhe nius activation parameter (E-D) and enthalpy of sorption (Delta H-s) were d etermined. The activation parameters are found to follow the conventional t rend. The poly(DMAm-co-VP) copolymers exhibited a decreased critical soluti on temperature (LCST) in proportion to their lactam content. Contact angle data were evaluated for the determination of surface free energy components (gamma(SV)(d), gamma(SV)(p) and gamma(SV)) of the synthesized polymers. Th e dispersion force component (gamma(SV)(d)) of copolymers increased only sl ightly with the VP content whereas the polar force component (gamma(SV)(p)) decreased with the lactam content. No dependence was observed between the surface free energy (gamma(SV)) and copolymer compositions. The complex for mation between bovine serum albumin (BSA) and the VP-DMAm copolymers in wat er was studied by fluorescence spectroscopy. It was found that the copolyme rs bind to BSA non-specifically on the surface. Phase separation was not ob served after addition of copolymers to BSA solutions at pH higher or lower than isoelectric point of BSA. (C) 2000 Elsevier Science Ltd. All rights re served.