Thermodynamics of micellisation and gelation of oxyethylene/oxypropylene diblock copolymers in aqueous solution studied by light scattering and differential scanning calorimetry

Abstract

Aqueous solutions of a range of diblock copolymers, each with one stat-copoly(oxyethylene/oxypropylene) and one oxyethylene block, were investigated by light scattering and differential scanning calorimetry. Critical micelle temperatures were measured by both techniques and the standard thermodynamic micellisation functions were derived. Enthalpies of micellisation determined directly from DSC were compared with the standard enthalpies of micellisation determined via the Gibbs–Helmholtz equation. Gelation temperatures were also measured and the standard thermodynamic gelation functions derived. Typical values of the standard enthalpies were 300 kJ (mol of chains)^–1 for micellisation and 30 kJ (mol of micelles)^–1 for gelation: the latter quantity corresponding roughly to 1 kJ (mol of chains)^–1.