Effect of phenolic cosolutes on the main parameters, phase separation and theta temperature of dilute aqueous poly(N-vinyl-2-pyrrolidone) solutions

The effect of phenolic cosolutes (phenol, catechol, resorcinol, hydroquinon e and phloroglucinol) on the main physicochemical parameters, cloud points (T-cp), phase diagram and theta temperature (Theta) of dilute aqueous poly( N-vinyl-2-pyrrolidone) (PVP) solutions was studied experimentally using var ious concentrations of cosolutes and polymers at different temperatures. Th e resulting dependence of T-cp and Theta temperatures (between 300 and 343 K) on the molar concentrations can be determined as sequences showing the d ecreasing effect of cosolute species in salting out the polymer. The decrea sing order of effectiveness of phenolic cosolutes in reducing both T-cp and Theta temperatures is phloroglucinol > resorcinol > hydroquinone > catecho l > phenol. It is shown that thermodynamic incompatibility of aqueous PVP/p henolic cosolute solutions strongly depends on the effect of the character of phenolic cosolute, changes taking place in the interactions among polyme r, solvent and additive phenolic cosolutes and on the change of water struc ture in the mixture. (C) 2000 Elsevier Science Ltd. All rights reserved.