Dynamic light scattering of semidilute hydrophobically modified alkali-soluble emulsion solutions with different lengths of poly(ethylene oxide) spacer chain

Semidilute solutions of hydrophobically modified alkali-soluble emulsion (HASE) were examined by dynamic light scattering and rheological techniques. For the model polymer without associative macromonomer, two q(2) dependent diffusional modes were detected in the decay time distributions. With increasing hydrophobicity of the associative macromonomer, the narrow fast peak was substituted by a shallow broad peak and only one q(2) dependent slow mode could be accurately detected, which indicated that the heterogeneity of these associated clusters increases with increasing carbon number. The bulk steady-shear viscosity exhibits similar results to the diffusion coefficients of the aggregate observed from light scattering measurements. The length of poly(ethylene oxide) (PEO) spacer chain alters the solution properties as well as the associative cluster structure. With increasing length of PEO spacer chain, intramolecular association was substituted by intermolecular association. For EO segment larger than 32 units, intramolecular association dominates, where the formation of HASE aggregates is controlled by the balance of electrostatic repulsion and hydrophobic attraction. (c) 2005 Wiley Periodicals, Inc.