SYNTHESIS AND PROPERTIES OF IONICALLY MODIFIED POLYMERS WITH LCST BEHAVIOR

Ionically modified LCST polymers were synthesized by free radical copo lymerization of N-isopropylacrylamide (NIPAM) with various cationic, a nionic, and amphoteric comonomers, resulting in products with comparab le molecular masses and charge concentrations. The temperature-depende nt phase transition behavior of the copolymers was investigated in wat er, aqueous sodium chloride solutions, and mixtures of water with dime thylformamide (DMF) using light transmission measurements, static ligh t scattering, viscometry, and sedimentation experiments in an analytic al ultracentrifuge. The LCST of the cationic modified copolymers remai ns unchanged compared with the homopolymer, but it is increased as a r esult of an amphoteric or anionic modification. Phase transitions are accompanied by conformational changes followed by aggregation processe s. These changes are enhanced in the presence of salt. The phase trans ition of poly-NIPAM-co-MADAMBQ ((methacryloyloxy)ethyl)dimethylbenzyla mmonium chloride) in 0.5 M NaCl was studied in detail investigating th e temperature dependence of molecular parameters as intrinsic viscosit y, particle mass, radius of gyration, second virial coefficient, and s edimentation coefficient.