Abstract
A hydrophobically-modified polyacrylamide and two partially hydrolyzed derivatives containing hydrophobic and carboxylic groups were prepared by micellar polymerization and post-hydrolysis. The molecular weight, second virial coefficient and radius of gyration were determined by static light scattering (SLS). Dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) were employed to determine the aggregate formation and type of chain packing in the semidilute regime, respectively. The behavior of solutions in dilute and semidilute regimes was also studied by viscometry and rheology. The hydrophobically-modified polyacrylamide showed a tendency to form aggregates due to the hydrophobic groups, but not enough to increase apparent viscosity. The partially hydrolyzed derivatives did not show the same aggregate-forming tendency. Rather, they exhibited anisotropic behavior, due to the charge density introduced into the polymer chain, which led to a more elongated macromolecular conformation and higher viscosity.
Highlights
Polyacrylamide polymers are widely used in oil and gas exploitation activities[1] and most acrylamide-Solution Properties of a Hydrophobically Associating PolyacrylamideJ
The results obtained here indicate that the nonhydrolyzed polymer PAHM-0 is more sensitive to salt than hydrolyzed polymers, forming aggregates at lower salt concentrations than PAHM-21 and PAHM-25
In the case of partially hydrolyzed polymers, the repulsion between the carboxylic groups hinders the formation of hydrophobic aggregates
Summary
Polyacrylamide polymers are widely used in oil and gas exploitation activities[1] and most acrylamide-Solution Properties of a Hydrophobically Associating PolyacrylamideJ. Solution Properties of a Hydrophobically Associating Polyacrylamide. (HAPAM) and their partially hydrolyzed analogues are prospective candidates as thickeners or rheology modifiers for use in drilling fluid formulations,[3] reservoir stimulation[4] and tertiary oil recovery.[5] Due to the association of hydrophobe moieties in nanodomains, their aqueous solutions exhibit remarkable rheological properties and better stability with respect to salts than the unmodified precursor, polyacrylamide (PAM) and partially hydrolyzed polyacrylamide (HPAM).[6] the effect of charged groups introduced into the polyacrylamide backbone of HAPAM remains a matter of debate in the literature. To the best of our knowledge, few studies to date have investigated HAPAMs containing both hydrophobic units and sodium acrylate units.[7,8,9]
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