Study of the rheological properties and solution microstructure of progressively cross‐linked aqueous gels

Abstract

AbstractA stepwise cross‐linking polyacrylamide hydrogel was prepared using the laboratory homemade stepwise crosslinker PVC‐PP‐Cr and partially hydrolyzed polyacrylamide. The microstructure was investigated by using the scanning electron microscope and dynamic light scattering. The results show that the system has a controllable cross‐linking time of 4 ~ 6 h, good heat resistance, and maximum gel strength of >300,000 mPa.S. In terms of viscoelastic behavior, a stepwise cross‐linking process between crosslinker and hydrolyzed polyacrylamide (HPAM) is presented, and the viscoelasticity is increased step by step. During the stepwise cross‐linking process, the dendritic structure, network structure and lamellar structure to a stable spatial network structure is obtained. Here, the cross‐linked structure between polymer molecular chains is formed after addition of the crosslinker, which increases the steric hindrance of macromolecular chains and further enhances the stability of the system. With the gradual release of chromium ions from the PVC‐PP‐Cr stepwise crosslinker, the gel system is formed continuously. When intermolecular friction stopped increasing, intermolecular entanglement and interaction are enhanced, and elasticity is also increased.