Rational modification of xanthan gum based on assistance of molecular dynamics simulation.

Graft copolymerization is an effective approach to improve performance of polysaccharide. However, selecting the most suitable modification strategy can be challenging due to the intricate molecular structure. Rational design through computer aided molecular dynamics (MD) simulations requires substantial computational resources. This study designed a simplified MD simulation strategy and suggested that grafting acrylamide (AM) could effectively adjust the molecular conformation of xanthan gum (XG) and its derivatives, thus regulating its viscosity and gelation properties. To rationally modify XG, a uniform experimental design was applied to tune the grafting ratios ranging from 72 % to 360 %, resulting in XG-AM solutions with viscosity ranging from 9 to 104 mPa•s at a concentration of 0.3 %. XG-AM was crosslinked by acid phenolic resin to generate gel with the viscosity of 7890 mPa·s in 3 days, which was 13 times the viscosity of unmodified XG. The controllable gelation will enhance the efficacy of XG-AM in oil recovery. By integrating rational selection of grafting strategies based on simplified MD simulation of polysaccharide derivatives and controllable grafting modification with specified grafting rates, customized production of polysaccharide derivatives can meet the requirements of a diverse range of applications.

Design of novel temperature-resistant and salt-tolerant acrylamide-based copolymers by aqueous dispersion polymerization.

Development of polymer-based flooding technology to improve oil recovery efficiency, water dispersion copolymerization of acrylamide, cationic monomer methacryloxyethyltrimethyl ammonium chloride (METAC), and anionic monomer acrylic acid (AA) were carried out in aqueous ammonium sulfate solution with polyvinyl pyrrolidone (PVP) as the stabilizer. The copolymers were characterized by 1H-NMR, FT-IR, TG, and SEM to confirm that they were prepared successfully and exhibited excellent salt-resistant property. Moreover, the effect of the aqueous solution of ammonium sulfate (AS) concentration, stabilizer concentration, and initiator concentration on the viscosity and size were systematically investigated. To further improve the thermal endurance properties of copolymer, hydrophobic monomers with different alkyl chain lengths were added to the above system. The acrylamide-based quadripolymer possessed prominent thermal and salt endurance properties by utilizing the advantages of zwitterionic structure and hydrophobic monomer. With the temperature rising, the viscosity retention could reach 70.2% in the water and 63.8% in the saline. This work had expected to provide a new strategy to design polymers with excellent salinity tolerance and thermal-resistance performances.