Synthesis and characterization of cellulose-based graft copolymers crosslinked by gamma-irradiation for enhanced oil recovery applications

Abstract

Cellulose-based polymers have garnered significant attention as potential candidates for use in enhanced oil recovery (EOR). The challenge in the design of EOR polymers is the need for materials with a high low critical solution temperature (LCST) and the ability to withstand harsh environmental conditions. In this study, cellulose-methylcellulose graft copolymers were prepared with different cellulose to methylcellulose weight ratios. The copolymerization was carried out using gamma radiation doses of 5, 15, and 25 kGy, respectively. The LCST of the copolymers were evaluated using differential scanning calorimetry analysis. The effect of salt addition on the LCST of the materials was studied using different phosphate-buffered saline (PBS) concentrations. The results showed that the cellulose monomer concentration increase from 0.1 to 0.5% in 2% methylcellulose dispersed in water reduced the LCST from 59 to 54°C. The hydrophobic nature of cellulose moieties induced the aggregation of the copolymers into core-shell micelles. Besides, higher gamma radiation doses lowered the LCST of the copolymers. The increase in the salt concentration in the PBS medium tended to decrease the LCST due to disrupted hydration structure of the polymer chains. This work revealed that cellulose-methylcellulose copolymers could be used in chemical EOR due to their high phase transition temperatures, preventing pore clogging and enhancing oil production in the producing wells.