A Hydroxypropyl Methyl Cellulose Based Graft Copolymer with Excellent Thermothickening

Thermothickening polymers are a novel material developed for enhanced oil recovery applications in high-temperature and high-salinity oil reservoirs. However, the existing synthesis process of thermoviscosifying polymers is complex and expensive, limiting the wide application of thermoviscosifying polymers. In this study, a thermothickening water-soluble polymer (PHAD) with a low concentration was synthesized by a "graft from" method, with acrylamide and diacetone acrylamide as grafted monomers and hydroxypropyl methylcellulose as the backbone chain. The basic parameters for PHAD copolymers were systematically studied compared to their homopolyacrylamide counterpart. The results show that the PHAD copolymers exhibited excellent thermothickening ability even when the polymer concentration was 0.2 wt % (total salinity is 9350.08 mg·L–1) upon increasing the temperature from 25 to 90 °C, where the apparent viscosity enhancement changes from 4.0 to 13.3 times with increasing the diacetone acrylamide content in PHAD copolymers. The PHAD copolymers also showed good salt tolerance, thermal stability, and viscoelastic properties under harsh reservoir conditions. These are attributed to the synergistic effect of the rigid heterocyclic ring structure and hydrophobic intermolecular forces association of thermoresponsive monomers within polymer chains.

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