HPAM-g-PEOPPO: Rheological modifiers in aqueous media of high temperature and high ionic strength

Partially hydrolyzed polyacrylamide (HPAM) is widely used as thickener in enhanced oil recovery (EOR), but the high temperature and salinity of oil reservoirs can reduce the viscosity and lead to polymer precipitation. To improve the performance of HPAM in high-salinity and high-temperature environments, the responsive amino-terminated poly(ethylene oxide-co-propylene oxide) (PEOPPO) (EO/PO = 19/03) was grafted onto a HPAM backbone. The copolymers were prepared in water using 1-ethyl-3-[3-(dimethylamino)-propyl]carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) as activators. Structural characterization was performed by H-1 NMR and Fourier transform infrared (FTIR) and the responsive behavior was investigated by UV-Vis and rheology. Spectroscopic analyses confirmed that copolymers were successfully synthesized. UV-Vis showed that copolymers have combined salt and thermoresponsive character. Rheology in saline medium (ionic strength = 3.75 mol.L-1) revealed that, contrary to unmodified HPAM, HPAM-g-PEOPPO have thermothickening behavior and also higher viscosity than HPAM at 70 degrees C, suggesting the utilization of these copolymers as rheological modifiers under harsh conditions of temperature and salinity, such as the ones found in EOR applications. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47453.