Article,
Elastic moduluS And Equilibrium Swelling Of Polyelectrolyte Gels
Macromolecules, 29 (1): 398--406 (1996)
Abstract
We present a scaling theory for the modulus G of polyelectrolyte gels
as a function of strand length between cross-links, monomer concentration
c, salt concentration c(s), and preparation conditions (monomer concentration
c(0) and salt concentration c(s)(0)). The theory assumes affine displacement
of the junction points when the concentration is changed. With no
added salt (c(s) = c(s)(o) = 0), we predict a new concentration dependence
of the modulus G similar to c(5/6). In the high-salt limit, we predict
the usual concentration dependence for uncharged polymers but a novel
dependence on salt concentration, G similar to c(7/12)c(s)(1/4).
We also predict the modulus to decrease as charge is added to the
gel strands. The predicted effects of added salt and charge on modulus
have recently been observed by Candau and co-workers. At low concentrations,
we discuss the strong stretching of network strands and its effect
on modulus and equilibrium swelling.
