Synthesis and Gelation Properties of Modified Silica Reinforced Quaternary Copolymer Poly(MSiO2/AA/AMPS/AM)

Synthesis of acrylamide-based polymers with excellent stability is crucial for oilfield applications. In this study, a novel modified silica nanoparticle (MSiO2) obtained by a two-step N-acylation reaction was used as a functional monomer to enhance the stability of poly(acrylic acid (AA)/2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)/acrylamide (AM)) ternary polymer (NSPM). A novel poly(MSiO2/AA/AMPS/AM) quaternary copolymer (MSPM) was obtained in this manner. The microstructure of MSPM was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The rheological properties of the MSPM were investigated based on the apparent viscosity in different salinities, temperatures, and shear rates. The MSPM exhibited improved stability compared with NSPM when the MSiO2 content was within the range of 0.14–0.20 wt %. This enhancement may be associated with hydrogen-bond-mediated intermolecular associations and MSiO2-centered branched or locally cross-linked structures formed during polymerization. Furthermore, the application of MSPM to gelation experiment showed that the grafting of MSiO2 effectively improved the gel strength of the polymer and prolonged its gel stabilization time from 10 to 14 days. The results of molecular dynamics simulation (MDS) demonstrate that the addition of MSiO2 effectively enhances the interaction between water and MSPM gel, which explains the fact that MSiO2 can reduce the dehydration rate of the MSPM gel.