ASSOCIATION AND SURFACE-PROPERTIES OF TAPERED STATISTICAL COPOLYMERS OF ETHYLENE-OXIDE AND BUTYLENE OXIDE IN WATER

Two statistical copolymers of ethylene oxide (EO) and 1,2-butylene oxi de (BO) of different compositions (80 and 60 mol% oxyethylene) were po lymerised (anionic polymerisation with monofunctional initiation) to 1 00% conversion, Their molar masses (M-n approximate to 5000 g mol(-1)) and molar mass distributions (M-w/M-n approximate to 1.06) were simil ar. The disparity in reactivity ratios in the EO/BO copolymerisation r esulted in pronounced composition drift along the chains (tapered stat istical copolymers) giving them the character of diblock copolymers. T he association behaviour of the copolymers in aqueous solution at 25 d egrees C was studied by dynamic and static light scattering and surfac e tension. It was confirmed that both formed micelles by a closed proc ess. Surface activity, as measured by surface tension lowering, was su perior to conventional EO/BO diblock copolymers with comparable micell e properties. Phase diagrams, determined over a wide concentration ran ge (c less than or equal to 70 wt.%), showed regions of gel formation (Liquid crystallinity) and clouding (phase separation).