Optimizing synthesis and application of an enhanced oil recovery agent: stability assessment of the optimized nanostructured PNIPAM/PS core–shell polymer using a developed DLVO-based model

Abstract

To improve the efficiency of hydrophilic polymers in oil reservoirs, a method encapsulates the polymer within a protective shell, safeguarding the core polymer and enabling controlled release in demanding, high-temperature conditions. Poly(N-isopropylacrylamide) nanoparticles are encapsulated with polystyrene shells through emulsion polymerization in this study. Varying the amounts of shell monmer and crosslinking agents resulted thick, sphere-shaped shells with homogeneous morphology, which protects the core polymer and enabling controlled release. Structural and morphological properties are characterized using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (H¹NMR), dynamic light scattering (DLS), and scanning electron microscope (SEM) imaging. Increasing the styrene amounts lead to larger particles, while higher crosslinker amounts result in a narrower size distribution. Thermal testing indicates heat resistance up to 300 °C, suitable for enhanced oil recovery (EOR) applications. Rheological tests determine an optimal 30-day release for the PNIPAM core, with the CS polymer showing increased viscosity under harsh conditions. The colloidal stability model estblished by Derjaguin, Landau, Verwey, and Overbeek (DLVO theory) and experimental results demonstrate good stability and energy barriers at room temperature, but decreased stability and increased agglomeration at higher temperatures. Thickening the styrene shell leads to particle agglomeration and unsuitable stability. The study confirms the effectiveness of the model in analyzing CS colloidal latex systems.

Graphical Abstract