Cloud points and Θ temperatures of aqueous poly(N-vinyl-2-pyrrolidone) solutions in the presence of denaturing agents

Cloud point curves have been determined for various concentrations of aqueous solutions of poly(N-vinyl-2-pyrrolidone) in the presence of a variety of denaturing agents (e.g. thiourea, guanidinium chloride and guanidinium carbonate). From these, a temperatures have been found. The resulting dependences of the critical temperature theta (between 320 and 350 K) on the molar concentration can be expressed as a sequence showing the increasing effect of denaturants in salting out the polymer. The increasing order of effectiveness of denaturing agents increasing the a temperature is guanidinium carbonate > guanidinium chloride > thiourea. The change of theta temperature by denaturing agents was found to be the result of the changes taking place in the hydrophobic/hydrophilic interactions among the polymer, solvent and additive denaturing agents, and of the influence of denaturing agent-polymer interactions. (C) 1997 Elsevier Science Ltd. All rights reserved.