Functional polymers for colloidal applications. VII. Aggregate formation of lipophile-modified polyacrylates in aqueous solutions

Abstract

AbstractWater‐soluble copolymers, poly(dodecyl acrylate–coacrylic acid) (PDA), are synthesized by copolymerizing different ratios of dodecyl–acrylate/acrylic acid. Their aqueous solutions are transparent. The plots of I1/I3 (the intensity ratio of pyrene emission at 374 nm and 385 nm) and of surface tension as a function of polymer concentrations are combined to verify the existence of the aggregates of PDAs. It is found that the aggregations begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I1/I3 as a function of polymer concentration shows that the polymers with a higher ratio of dodecyl acrylate form polymer aggregates at lower concentrations. The hydrophobicity of the inner core of polymer aggregates is close to that of sodium dodecyl sulfate (SDS). Polymer solutions of PDA 30, PDA 30L, and PDA 15, show significant solubilization ability to pyrene. (The molar ratio of dodecyl acrylate/total acrylates is 30%, 30%, and 15% for PDA 30, PDA 30L, and PDA 15, respectively. L, low molecular weight.) The solubilization ability increases with the increase in polymer concentration and degree of substitution of dodecylamine. The intensity ratio of the excimer emission to monomer emission of pyrene (Ie/Im) increases with increasing polymer concentration, roughly parallel to the increase in the amount of pyrene solubilized. However, the Ie/Im at a fixed pyrene concentration (Ie/I) decreases with increasing polymer concentration. These phenomena are interpreted in terms of the amount of pyrene solubilized and the size and concentration of the polymer aggregates. © 1993 John Wiley & Sons, Inc.