States of water in cationically charged poly(vinyl alcohol) membranes

Abstract

Differential scanning calorimetry (d.s.c.) and pulsed 1H nuclear magnetic resonance (n.m.r.) measurements were carried out on cationically charged poly(vinyl alcohol) (PVA) membranes to obtain information about the states of water in polymer matrices. From the d.s.c. data, water present in the polymer matrices is classified as (i) freezable and (ii) non-freezable, whereas n.m.r. measurements indicate its classification into (i) free and (ii) bound water. The amounts of free and bound water depend on the mobility of polymer chains and distinguish between freezable and non-freezable. The correlation time obtained from spin-lattice relaxation indicates that the mobility of water in poly[vinyl alcohol- co-( N-(3-trimethylammoniopropyl)-acrylamide chloride)] (PVA-N) membranes (H = 0.358) is approximately 10 4 times shorter than in bulk water.