SWELLING SHRINKING KINETICS OF CHEMICALLY CROSS-LINKED POLY(VINYL ALCOHOL) GELS IN THE PRESENCE OF BORATE IONS/

The swelling/shrinking kinetics of chemically cross-linked poly(vinyl alcohol) (PVA) gels with berate ions has been studied by measuring the gel size as a function of time. The experimental process consisted of two steps, i.e., (I) immersion of a gel in a mixture of NaOH and bori c acid aqueous solutions. and (II) subsequent immersion in deionized w ater or in a NaOH solution without berate ions. In step I, the gel swe lled or shrank depending on the berate ion concentration and reached i ndividual equilibrium values within 5000 min. After equilibration, the gel was transferred to the second bath and step Il was initiated. Whe n a gel was immersed in deionized water, the gel swelled considerably and then deswelled gradually to the original size. On the other hand, when a gel was dipped in a bath containing NaOH, a reverse process of step I took place and the gel size gradually reduced to the original s ize. The diffusion coefficients in these steps are discussed in conjun ction with those obtained by dynamic light scattering. (C) 1996 Americ an Institute of Physics.