Precipitation polymerization of hydrophobically modified polyelectrolyte poly(AA-co-ODA) in supercritical carbon dioxide and solution rheology properties

다국어 초록 (Multilingual Abstract)

Hydrophobically modified (HM) polyelectrolytes were prepared by using precipitation polymerization of acrylic acid (AA) and octadecyl acrylate (ODA) in various molar ratios in supercritical carbon dioxide. The product was obtained in the form of a white powder and the micrographs show aggregates of primary particles < $1{\mu}m$ in size. The effects of polymer concentration, ODA content in polymer, surfactant, shear time, shear rate on the apparent viscosity were investigated. The reason leaded to a significant viscosity enhancement was discussed. Steady-state and oscillatory tests of solution were also investigated. Solution exhibited shear thinning behavior and thixotropy. Polymers contain octadecyl acrylate (3.4 mol%) at 0.2 g/dL behaved as high entanglement structures or association gels, since the modulus $G^{\prime}$ were being higher than $G^{{\prime}{\prime}}$ throughout the frequency range. The comparison of apparent and complex viscosities confirmed the association gel properties.