Influence of bound water on viscoelastic enhancement in aqueous disperse systems of ionic microgels

Abstract

The viscoelastic properties have been measured by means of a cone–plate-type rheometer for aqueous disperse systems of ionic microgels. Marked viscoelastic enhancement was observed in some aggregate systems in which anionic and cationic particles were mixed. The dynamic viscoelastic functions of these aggregate systems were enhanced ca. 10⁵ times with respect to those of non-aggregate systems, suggesting that the aggregate contains a large quantity of bound water which is tightly arranged in the electrostatic potential field between oppositely charged particles. The bound water was investigated by d.s.c., dielectric measurements and n.m.r. spectroscopy. Two kinds of bound water were detected by d.s.c. and dielectric measurements. The dielectric relaxation time of the bound water which seems to take part in the viscoelastic enhancement was ca. 8.9 × 10^–9 s.