Kinetics of Polymer/Metal-Ion Gelation

Abstract

ABSTRACT Polyacrylamide and partially hydrolyzed polyacrylamide solutions can be crosslinked by tri-valent chromium ions to form stable gels. In this study the kinetics of the gelation reaction are determined from the time dependence of dynamic mechanical measurements using classical network elasticity theory to relate the storage modulus of the gel to the number density of crosslinks. The reaction is second order in chromium ion concentration corroborating previous reports of a bi-molecular chromium ion complex. Gelation studies with anionic and nonionic polyacrylamides in NaCl, KI, and Na2SO4 solutions show that electrostatic interactions between chain segments alter the rate of reaction. The effects are successfully modeled using electrostatic theories of Odijk and Fixman.