Neighboring group effect on the thermal degradation of polyacrylamide and its derivatives

Abstract

Abstract Being an important class of water-soluble synthetic polymers, polyacrylamide (PAM) and its derivatives have found a wide range of applications in the oil and gas industry. Due to the increasingly active exploration of deep and ultra-deep wells, PAM-based polymers are more and more frequently applied under hostile subterranean conditions, particularly high temperature. Therefore, it becomes an imminent research topic to elucidate the thermal degradation pathways of PAM-based polymers in order to upgrade these chemicals for more challenging scenarios. Neighboring groups attached to the same polyvinyl backbone have been suggested to exert an effect to the degradation of the PAM-based polymers. Herein we report a combined theoretical and experimental study on the energetics of such neighboring group effect. Taking advantage of a computational method based on density functional theory, we have identified two competing degradation pathways in neutral medium and have calculated their respective activation energies. These results enable us to predict the relative thermal stabilities of a series of PAM-based polymers, and we have also used temperature-variant rheology measurements to verify these predictions. This work will guide the design of better heat-resistant PAM-based products.