Gelation of a new hydrogel system of atactic-poly(vinyl alcohol)/NaCI/H2O

alpha-PVA/NaCl/H2O hydrogels have been prepared by gelation of aqueous atactic-poly(vinyl alcohol) (alpha-PVA) solutions in the presence of NaCl. The gelling temperature, melting temperature and the preservation of water of the hydrogels have been measured. The effect of the addition of NaCl to the hydrogels on gelling temperature and melting temperature is marked when the NaCl concentration is over a certain value. High NaCl concentration favours high-melting-point hydrogels. When the NaCl concentration is high enough (such as 11%), high-melting-point and white turbid opaque alpha-PVA/NaCl/ H2O hydrogels can be prepared, regardless of the PVA concentration. Similarly, the low gelling temperature of alpha-PVA/NaCl/H2O solutions comes from low NaCl concentration, while high gelling temperature ranges from 50 to 70'C when the NaCl concentration is 11%. In appearance, the types of syneresis of alpha-PVA/NaCl/H2O are chi-type or a mixture of chi- and n-types; water release of the hydrogels is slowed down by the addition of NaCl. (C) 2002 Society of Chemical Industry.