Study on association behavior and solution properties of poly(acrylic acid-alkyl polyoxyethylene acrylate) amphiphilic copolymers

Hydrophobically associating water-soluble polymers (HAWSPs), which possess surfactant and polymer properties, are extensively studied. This research work presents a novel HAWSP, poly(acrylic acid-alkyl polyoxyethylene acrylate) (P(AA-AAEO_n)), synthesized by aqueous polymerization of acrylic acid and alkyl polyoxyethylene acrylate (AAEO_n) with various ethoxy groups. The structure of P(AA-AAEOn) was characterized using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. The association behavior in the solution was also evaluated through surface tension, dynamic light scattering, and rheology measurements. The findings exhibited that P(AA-AAEO_n) demonstrated noteworthy surface activity, which was amplified as the proportion of the hydrophobic group increased and could effectively reduce the water surface tension. When the concentration reached 0.01%, P(AA-AAEOn) in the solution changed from intramolecular association to intermolecular association. Additionally, P(AA-AAEO_n) manifested notable shear resistance, shear recovery, and viscoelasticity, transitioned from energy elasticity to entropy elasticity in P(AA-AAEO_n) molecules between 25 and 35 ℃. The experimental phenomena and mechanisms resulting from the association behavior of polymer molecules have undergone careful analysis. The elastic conversion of polymer molecules at varying temperatures is a noteworthy finding, which has not been extensively documented in earlier research works. A detailed analysis of this phenomenon has been conducted. However, further research is crucial to establish the prevalence of this phenomenon in HAWSPs.

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