Cooperative association of diblock and triblock copolymers in aqueous solution. A study of mixed micelles of block-copoly(oxyethylene/oxybutylene) and block-copoly(oxybutylene/oxyethylene/oxybutylene)

Abstract

Block copolymers of ethylene oxide and 1,2-epoxybutane, B₈E₄₁ and B₁₂E₇₆B₁₂, have been synthesized and purified, and their association properties in aqueous solution studied by surface tension and static and dynamic light scattering. A 50 : 50 wt.% mixture of the two copolymers in dilute aqueous solution formed mixed micelles in which the triblock copolymer molecules were predominantly in the looped conformation. At higher concentrations (e.g. 100 g dm^–3) the mixed micelles themselves associated to form micellar clusters which were bridged by triblock copolymers in the extended conformation. The results include micelle and cluster association numbers.