Effect of the surfactant head group length on the interactions between polyethylene glycol monononylphenyl ethers and poly(acrylic acid)

The behavior of homogeneous and polydisperse ethoxylated nonylphenols in th e presence of poly(acrylic acid) (PAA) was investigated by fluorescence, su rface tension, viscometric and pH measurements. Critical micelle concentrat ion (CMC), critical aggregation concentration (CAC or T-1) and various othe r critical points of interaction such as the appearance of free surfactant molecules at the air/water interface (T-2') and of micelles into solution ( T-2) were determined. For polydisperse surfactants, the surface excess, are as per molecule and the composition of polymer-surfactant complexes were al so established. T-1 was lower than CMC and was not influenced significantly by the length and dispersity of the poly(ethylene oxide) (PEO)chain. For t he polydisperse surfactants, T-2' and T-2 decrease with increasing PEO chai n length. The PAA practically does not affect the area per molecule, irresp ective of the ethoxylation degree. The results suggest that complexes origi nate from hydrogen bonding and are further stabilized by hydrophobic intera ctions of the surfactant tails. (C) 1999 Elsevier Science B.V. All rights r eserved.