Thermodynamics of Aggregation and Modulation of Rheo-Thermal Properties of Hydroxypropyl Cellulose by Imidazolium Ionic Liquids

Mixtures based on cellulose derivatives/ionic liquids (ILs) are potential viscosity modifiers for enhanced oil recovery (EOR). This paper investigates the thermodynamic of monocationic imidazolium ionic liquids (1-alkyl-3-methylimidazolium bromide, CnMIMBr) aggregation with hydroxypropyl cellulose (HPC) in the dilute regime and the modulation of its rheological and thermal properties in the semi-dilute regime. The outcomes showed that binding occurs by hydrophobic interactions between the alkyl chain of ILs and hydroxypropyl group on HPC and by ion-dipole interactions, and it is driven by entropy. The addition of ILs produced a significant increase in the HPC solutions' viscosity, which depends on the concentration and alkyl chain length of the ILs (n = 10, 12, 14, 16). Moreover, the presence of ILs produces an effect salt-in delaying the HPC phase separation. These findings highlight the role of ILs on the rheological and thermal properties of HPC, opening new possibilities for the design of new complex mixtures. (C) 2022 Elsevier B.V. All rights reserved.