Aggregation behavior of hydrophobically modified polyacrylate in aqueous solution

The aggregation behavior of copolymer (PAMB), which was synthesized by the means of emulsion polymerization with acrylic acid (AA), methacrylic acid (MA), methyl methacrylate (MMA) and butyl acrylate (BA), was studied by surface tension and fluorescence probe technologies. The critical micelle concentrations (cmc) of PAMB in aqueous solution by surface tensiometry, and thereby the thermodynamic parameters in formation of PAMB aggregate were calculated; the variation of the intensity ratio of the first and third vibrational bands (I1/I3) of pyrene in aqueous PAMB solution was employed to examine the microscopic polarity of PAMB aggregate. The results show that the PAMB is easy to aggregate at the air/liquid interface, which leads to the remarkable decrease of surface tension of water. It also readily forms micelle-like aggregate in aqueous solution, which forms microdomain to solubilize the hydrophobic probe pyrene. The entropy is highly important in the process of forming PAMB aggregate. The results on surface tensions of PAMB/polyvinylpyrrolidone (PVP) and PAMB/dodecyloxypropyl β-hydroxyl trimethyl-ammonium bromide (C12NBr) systems indicated that the aggregation behavior of PAMB was different from anionic surfactants with low molecular weight and from water-soluble polymers, too.