SOLUBILIZATION PROPERTIES OF NON-IONIC SURFACTANT-POLYMERIC ACID COMPLEXES

The complex of a polyoxyethylene-type nonionic surfactant and a polymeric acid (polyacrylic and polymethacrylic acids) in aqueous solution has a different solubilization power from that of the micelles of the surfactant solution alone. From solubilization experiments it was found that the binding of the surfactant to a polyacid becomes abruptly conspicuous above a certain surfactant concentration, which is lower than the CMC of the surfactant. This critical concentration is considered as the concentration at the beginning of the micelle-like binding of the surfactant on the polyacid and is denoted as CMCp. CMCp is dependent upon the concentration of the polyacid when it is dissociated or at low concentrations, but is constant when undissociated and the ratio surf actant/polyacid is not too small. CMCp is also dependent on the kind of polyacid, and on the degree of polymerization only in the low range. CMCp is independent of temperature. In a series of nonionic surfactants of the same lipophilic moieties, the effect of polyacid addition on the CMCp is the larger the longer the polyoxyethylene chain. The interaction between polyacid and solubilizate plays a key role in the solubilization by the complex. © 1979 Dr. Dietrich Steinkopff Verlag.