Hydrophobically Associating Polyacrylamide “Water-in-Water” Emulsion Prepared by Aqueous Dispersion Polymerization: Synthesis, Characterization and Rheological Behavior

Abstract

The hydrophobically associating polyacrylamide (HAPAM) is an important kind of water-soluble polymer, which is widely used as a rheology modifier in many fields. However, HAPAM products prepared in a traditional method show disadvantages including poor water solubility and the need for hydrocarbon solvents and appropriate surfactants, which lead to environmental pollution and increased costs. To solve these problems, we reported a novel kind of HAPAM “water-in-water” (w/w) emulsion and its solution properties. In this work, a series of cationic hydrophobic monomers with different alkyl chain lengths were synthesized and characterized. Then, HAPAM w/w emulsions were prepared by the aqueous dispersion polymerization of acrylamide, 2-methylacryloylxyethyl trimethyl ammonium chloride and a hydrophobic monomer. All these emulsions can be stored more than 6 months, showing excellent stability. An optical microscopy observation showed that the particle morphology and the particle size of the HAPAM emulsion were more regular and bigger than the emulsion without the hydrophobic monomer. The solubility tests showed that such HAPAM w/w emulsions have excellent solubility, which took no more than 180 s to dilute and achieve a homogeneous and clear solution. The rheology measurements showed that the HAPAM association increases with a hydrophobe concentration or the length of hydrophobic alkyl chains, resulting in better shear and temperature resistances. The total reduced viscosity was 124.42 mPa·s for cw101, 69.81 mPa·s for cw6-1, 55.38 mPa·s for cw8-0.25, 48.95 mPa·s for cw12-0.25 and 28 mPa·s for cw16-0.25 when the temperature increased from 30 °C to 90 °C. The cw8-2.0 that contains a 2 mol% hydrophobe monomer has the lowest value at 19.12 mPa·s due to the best association. Based on the excellent stability, solubility and rheological properties, we believe that these HAPAM w/w emulsions could find widespread applications.

Influence of Alkyl Chain Length on the Performance of Inverse Emulsion Polyacrylamide Fracturing Fluid Thickeners

“…Consequently, these limitations restrict the hydrogel’s utilization in actual construction. To address the issue of slow dissolution associated with the product derived from the aforementioned method, certain scholars have turned to water-in-water emulsion polymerization as an alternative approach for preparing PAMs. , The resulting polymer from this method exhibits an emulsion-like nature, allowing for rapid dispersion and dissolution in water. This characteristic enables its utilization and compatibility within the construction process.…”

Functional Materials Made by Combining Hydrogels (Cross-Linked Polyacrylamides) and Conducting Polymers (Polyanilines)—A Critical Review

“…The use of polyacrylamide as gel media for electrophoresis makes it the most commonly in situ synthesized material [ 2 ]. Moreover, using functionalized acrylamides as monomers, it is possible to produce hydrophilic [ 3 ], or hydrophobic gels [ 4 ], thermosensitive (“smart”) materials [ 5 ], polyelectrolytes bearing positive [ 6 ] or negative charges [ 7 ], etc. The hydrophilic gels swell strongly (>20.000%) in water [ 8 ], and the more hydrophobic polymers also swell in nonaqueous solvents [ 9 ].…”