PHASE-SEPARATION BEHAVIOR OF POLYMERS IN WATER - TEMPERATURE AND SURFACTANT EFFECT

The phase separation behaviour of a sample of poly(N-vinyl-2-pyrrolido ne) (PVP) in aqueous Na2SO4 (0.55 M) containing a surfactant, sodium d odecyl sulfate (SDS), is studied with temperature and surfactant conce ntration as independent variables. Without surfactant, the polymer exh ibits a lower solution temperature (LCST) of 28 degrees C, above which it precipitates. At SDS concentrations of only 300 mg L-1, aggregatio n is prevented and the behaviour of isolated polymer molecules can be studied. Measurements of hydrodynamic radius (R-H) and intrinsic visco sity [eta] of PVP in Na2SO4 (0.55 M) have been performed by using Dyna mic Light Scattering (DLS) and viscometry. From these results, a coil- to-globulule phase transition was detected as a function of temperatur e at constant SDS concentreation. (C) 1997 Elsevier Science Ltd.