SOME CRITICAL-POINTS IN THE INTERACTION BETWEEN HOMOGENEOUS NONIONIC SURFACTANTS AND POLY(ACRYLIC ACID)

Single hexaethylene glycol mono(n-dodecyl) ether or octaethylene glyco l mono(n-dodecyl) ether in aqueous solution and their mixtures with po ly(acrylic acid) (PAA) were studied by surface tension, fluorescence, dye solubilization, viscosity and pH methods. The CMC and several crit ical surfactant concentrations for the interaction were determined. Th e starting point of micellar aggregation on the PAA chain (T-1) and th e point at which free micelles appeared in the solution were found and identified by the various methods. The concentration at which free su rfactant molecules reappear in the system, was a transitional range ra ther than a critical point and was identified with certainty only by s urface tension measurements. The data were discussed taking into accou nt the interaction of both ethoxylated and hydrophobic moieties of the surfactant with PAA (i.e. hydrogen bonding and hydrophobic bonding re spectively). Finally, the relationship between T-1 and the ethoxylated and hydrophobic moieties of the surfactants was considered.