Demulsification Performance of Thermosensitive Copolymer Poly(DMDAAC-co-DEA) in O/W Crude Oil Emulsions

The polymers of N , N -diethylacrylamide (DEA) exhibit temperature-dependent sensitivity attributable to the presence of both hydrophilic and hydrophobic groups. However, their lower critical solution temperature (LCST) is only 25 °C, a limitation that restricts their practical applications. Previous studies have shown that the incorporation of cationic monomers for copolymerization can enhance the LCST of polymers. In this study, dimethyldiallylammonium chloride (DMDAAC) and DEA were selected for copolymerization to obtain a series of thermosensitive water-soluble polymers, poly(DMDAAC- co -DEA). Structure and properties were characterized using FT-IR, 1 H NMR, TG-DSC, and surface tension test. Combined with the critical phase transition mechanism, it was determined that the hydrophilicity of the polymer underwent a gradual increase in proportion with the increase of DMDAAC blocks in polymers, and the LCST exhibited an increase of up to 36.8 °C. The relationship between polymer structure and demulsification performance was also explored, as represented by the application of O/W emulsion. The experimental findings demonstrated that all poly(DMDAAC- co -DEA) products exhibited effective demulsification performance. The demulsification rate of the polymers with 30%, 50%, and 70% of DMDAAC could reach 97.03%, 98.20%, and 98.40% respectively, which shows great potential for the petroleum demulsification application. Graphical Water-soluble polymer Poly(DMDAAC- co -DEA) are synthesized using a three-step heating method. A comprehensive investigation is conducted into the relationship between its LCST and copolymerization ratio, resulting in the elucidation of the underlying mechanism. Furthermore, the demulsifying properties of the copolymer are investigated.