Synthesis and characterization of pH‐sensitive poly(acrylamide‐co‐methylenebisacrylamide‐co‐acrylic acid) hydrogel microspheres containing silica nanoparticles: Application in enhanced oil recovery processes

ABSTRACT In this study, pH‐sensitive hydrogel microspheres consisted of acrylamide (AAm) and acrylic acid (AA) monomers, and silica nanoparticles (SNPs) were synthesized via inverse suspension polymerization. To find a proper formulation for synthesis of these microspheres, design of experiment was performed using the input parameters, such as stirring rate, AA/AAm ratio, and the amount of SNP content. Scanning electron microscopy micrographs indicated that mean size of the microspheres decreased by increasing the stirring rate and SNP content and by lowering the AA/AAm ratio. Moreover, morphological survey of the microparticles exhibited a spherical shape with smooth surface. Swelling behavior of the produced hydrogels was investigated in four different environments. The results showed that a decrease in temperature and an increase in salinity led to reduction of the equilibrium swelling ratio (SR) to some extent. Moreover, increasing the pH caused a drastic increment of the equilibrium SR. Response surface methodology approach was utilized to establish a functional relationship between the effective parameters for synthesis of hydrogels and their favorable SR. Finally, performance of the resultant hydrogels was visually examined in enhanced oil (EOR) recovery processes in two steps. The flooding test of the hydrogel spheres indicated 23% increase in oil recovery factor in comparison to water flooding. This observation revealed the potential efficiency of the synthesized hydrogels for EOR applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48491. HIGHLIGHTS Using inverse suspension method to synthesize spherical hydrogels containing nanosilica. Investigation on the effects of temperature, water salinity, and pH on equilibrium swelling ratio of hydrogels. Investigation on rheological characterization of the synthesized hydrogels by adding nanosilica. Studying on the effect of synthesized hydrogels in macroscopic sweep efficiency using micromodels. Application of the synthesized hydrogels for core‐flood tests and studying the oil recovery factor.