Design of salt-responsive low-viscosity and high-elasticity hydrophobic association polymers and study of association structure changes under high-salt conditions

Abstract

A hydrophobic associative water-soluble polymer, SRHV, was designed and synthesized in this study. The CAC of SRHV was 0.072 wt% and 0.2 wt%. The scanning electron microscopy tests showed that the polymer demonstrated a multilayer network structure. Rheological tests revealed that polymer solution exhibited low-viscosity and high-elasticity rheological behaviors under high-salinity conditions and this salt-responsive behavior persists at high temperatures. Fluorescent probe tests confirmed that salt addition promoted the formation of hydrophobic association networks. Through molecular dynamics simulation, various parameters, such as mean square displacement (MSD), radius of gyration (Rg), and radial distribution function (RDF), were analyzed to further explain the salt-tolerance mechanism of SRHV and the effect of salt ions on the hydrophobic association structure. The results showed that the viscosity and elasticity of polymers were not necessarily correlated. In addition, elasticity dominated when the positive effect of salt-promoted association exceeded the negative effect of salt-coiled molecular chains and polymer relies on elasticity to achieve an excellent sand-carrying effect at this time. In general, SRHV exhibits great potential for application in oil fields with high salt environment, which could effectively reduce the waste of freshwater resources. Furthermore, this work provides some support for suspending sand relying on elastic.