Study of cryostructuration of polymer systems. XV. Freeze-Thaw-induced formation of cryoprecipitate matter from low-concentrated aqueous solutions of poly(vinyl alcohol)

Abstract

Freeze–thaw treatment of low-concentrated (<C*) aqueous solutions of poly(vinyl alcohol) (PVA) results in the formation of a cryoprecipitate fraction. It is shown that the efficiency of such a process (the yield of PVA cryoprecipitation) depends on the initial polymer concentration in the solution to be frozen and the conditions of a cryogenic influence. The key factor is defrostation dynamics: The slower the thawing rate, the higher the cryoprecipitation yield. The iodine-staining method is employed for the quantitative analysis of PVA concentrations in the solutions under study and the necessity of the use of reduced (0–2°C) temperatures throughout such a PVA quantification is demonstrated. Observation of the kinetics of the freeze–thaw-induced formation of cryoprecipitate matter reveals the extreme character of the temperature dependence of the efficacy of PVA macromolecule aggregation, the extreme point being situated in the vicinity of −2°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1978–1986, 1999