DYNAMIC LIGHT-SCATTERING-STUDIES ON POLYELECTROLYTIC DERIVATIVES OF POLY(N-ISOPROPYLACRYLAMIDE)

Copolymers of N-isopropylacrylamide, 2-acrylamido-2-methylpropane sulf onic acid, and 2-acetamidoacrylic acid in various ratios were synthesi sed by free radical solution polymerisation. Aqueous solutions of the copolymers were studied by dynamic light scattering in order to find o ut how the lower critical solution temperature and the conformational transition of the polymers st that temperature depend on the chemical composition of the macromolecule. The ratio of the hydrophobic and hyd rophilic repeating units was observed to affect considerably the respo nse of the polymers to an increase in temperature. The polyelectrolyte s were studied also in aqueous salt solutions. The salts added into th e solutions were sodium, nickel and chromium chlorides. The behaviour of the polymers was observed to depend on tile chemical nature of the added inorganic salt as well as on the ionic strength of the solutions . The added salts increase the tendency of the polymers to aggregate i n solutions. The degree of aggregation, however, is not only dependent on the ionic strength; different cations clearly show a different cap ability of binding to the polymers. (C) 1997 Elsevier Science Ltd.