Effect of crosslinker on swelling and thermodynamic properties of polyacrylamide gels

Abstract

PAA networks have been prepared by crosslinking copolymerization of acry- lamide (AA) and N,N'-methylen-bis-acrylamide (BA) in water. The degree of swelling was measured in the range v2 =0-0.16 as a function of crosslinker proportion, C (%w/w) and total concentration, Cr (g/ 100 ml). The swelling of two networks with BA contents of 3 ,;; and 10% were measured as a function of temperature in the range 10-30°C. The interpretation of elastic and swelling data in terms of the scaling law lfh I =Av 2m, shows a transition from a good solvent regime to a collapsed state for the polymer chains, when the crosslinker proportion is around 5 to 7%. Results of elastic and swelling measurements were used to determine the x parameter. A different dependence of x with v2 was found for gels with BA contents below and above 5-7%. The enthalpic contribution to the interaction parameter XH was calculated from swelling experiments as a function of temperature. The results show that when the BA proportion is increased, the enthalpic