Gelation of diblock copoly(oxyethylene/oxybutylene) in aqueous solution

Abstract

The gelation of concentrated aqueous micellar solutions of three diblock copoly(oxybutylene/oxyethylene)s (E₅₀B₁₃, E₄₉B₈ and E₂₄B₁₀, where E represents oxyethylene and B represents oxybutylene) was investigated. The gel regions of the temperature–concentration diagrams were identified, including the lower and upper temperature gel–sol boundaries. The effect on gelation of micellar mass and size (which were known for the systems under investigation) was determined, and shown to be consistent with the packing of micelles modelled as hard spheres. The thermodynamics of gelation was investigated, and the derived quantities compared with those reported previously for related triblock copolymers (E_mB_nE_m). The mechanism of gelation at high and low temperatures is discussed, the former being related to the effect of temperature on micellar swelling, and the latter to ongoing micellisation.