Aggregation behaviour of Pluronic® L64 surfactant at various temperatures and concentrations examined by dynamic light scattering and viscosity measurements

Abstract

AbstractThe aggregation behaviour of poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO) triblock copolymers (Pluronic® L64 surfactant) in water was examined using several independent methods. The measurements were performed with solution temperatures in the range 34–52 °C and with L64 aqueous solution concentrations in the range 33–67 mg mL−1. The dynamic light scattering (DLS) by ‘photon beat’ technique showed the existence of two regimes separated by one critical temperature at around 45 °C, and one critical concentration around 50 mg mL−1. For the two regimes, we observed abnormalities in the particle structure and shapes due to the effects of temperature and concentration on the aggregation behaviour. Thus, the size of particles in aqueous solution strongly depends on the kinds of interaction and the balance between excluded volume effects and hydrophobic forces. Some viscosity measurements were also performed to complete the DLS measurements and to provide more information on the particle structure. Copyright © 2005 Society of Chemical Industry