Light scattering of hydrophobically modified alkali-soluble emulsion (HASE) polymer: Ionic strength and temperature effects

Novel hydrophobically modified alkali-soluble emulsion (HASE) polymers cons isting of methacrylic acid (MAA) and ethyl acrylate (EA) backbone with smal l amounts of hydrophobic macromonomers grafted to it were synthesized for t he present study. The pH. ionic strength as well as temperatures significan tly alter the dilute solution properties. At low pH and without the additio n of a base, the polymer is water-insoluble and exists as latex. When a bas e is added, the methacrylic acid groups are neutralized and the polymer sol ubilizes. The apparent hydrodpnamic size increases to a maximum, then decre ases to a minimum and thereafter increases to a constant value. With increa sing salt concentration, the apparent diffusion coefficients of aggregates and unimers increase and this behavior differs from that of pure polyelectr olyte solutions. Fractal dimensions from intensity light scattering reveal that the structure becomes more compact with increasing salt concentration. A pictorial description of the microstructure at low and high ionic streng th is proposed, based on the results of both dynamic and static light scatt ering, Meanwhile, increasing temperature yields correspondingly higher appa rent diffusion coefficients? which can be described by the Arrhenius relati onship. However, the reduced diffusion coefficients, fractal dimensions as well as the apparent hydrodynamic sizes are independent of temperature.