J. Sharma et Hb. Bohidar, Quasielastic light scattering study of chemically crosslinked gelatin solutions and gels, COLLOID P S, 278(1), 2000, pp. 15-21
Quasielastic light scattering measurements are reported for experiments per
formed on mixtures of gelatin and glutaraldehyde (GA) in the aqueous phase,
where the gelatin concentration was fixed at 5% (w/v) and the GA concentra
tion was varied from 1 x 10(-5) to 1 x 10(-3)% (w/v). The dynamic structure
factor: S(q, t), was deduced from the measured intensity autocorrelation f
unction, g(2)(tau), With appropriate allowance for heterodyning detection i
n the gel phase. The S(q, t) data could be fitted to S(q: t) = A exp(--D(f)
q(2)t)t B exp(-t/tau(c))(beta), both in the sol (50 and 60 degrees C) and g
el states (25 and 40 degrees C). The fast-mode diffusion coefficient, Dc sh
owed almost negligible dependence on the concentration of the crosslinker G
A; however, the resultant mesh size, xi, of the crosslinked network exhibit
ed strong temperature dependence, xi similar to (0.5 - x)(1/5) exp(-A/RT) i
mplying shrinkage of the network as the gel phase was approached. The slow-
mode relaxation was characterized by the stretched exponential factor exp(-
-t/tau(c))beta. beta Was found to be independent of GA concentration but st
rongly dependent on the temperature as beta = beta(0) + beta(1)T + beta(2)T
(2) The slow-mode relaxation time, t,, exhibited a maximum GA concentration
dependence in the gel phase and at a given temperature we found tau(c)(c)
= tau(0) + tau(1)c +tau(2)c(2). Our results agree with the predictions of t
he Zimm model in the gel case but differ significantly for the sol state.