Mechanism of silica nanoparticles' better-thickening effect on amphiphilic polymers in high salinity condition

Abstract

Recently, the composite materials developed by the combination of polymer and inorganic nanomaterial have gained various attraction for researchers. In this paper, the negative charged silica nanoparticles (silica NPs) with hydroxyl groups on the surface were mixed with the amphiphilic polymer having positive charged hydrophobic groups to form a NP-polymer composite at the high temperature and high salinity condition. The thickening mechanism of silica NPs on amphiphilic polymers in high salinity condition was analyzed by measuring the viscosity and viscoelasticity of solution compared with HPAM. In order to clarify the function of the spatial network structure, the β-cyclodextrin (β-CD) was used to destroy the associated structure, and the microstructure was analyzed by scanning electron microscopy (SEM). Results revealed that the apparent viscosity and viscoelasticity of the polymer solution significantly increased only by involved silica NPs, and a viscous system also turned into an elastic one increasing. This study concludes that silica NPs collaborate with the hydrophobic association structure formed by the amphiphilic polymer due to electrical interaction and hydrogen bond. Thus, silica NPs can strengthen the spatial network structure. This kind of composite material provides a new way to increase the viscosity of the polymer at elevated temperature, and enhances its application in high salinity reservoirs.