Association and Surface Properties of a Cyclic Block Copolymer of Ethylene Oxide and Butylene Oxide (Cyclo-B₈E₄₂) in Water

A cyclic copolymer of ethylene oxide and 1,2-butylene oxide (cyclo-B 8 E 42 ) was prepared by cyclization of triblock copolymer E 21 B 8 E 21, and its self-association and surface properties were studied by dynamic and static light scattering and surface tension. Critical micelle concentration (cmc), micellar molar mass and size, and molecular areas at the air−water interface were compared with corresponding quantities measured previously for linear triblock and diblock copolymers of similar chain length and composition (E 21 B 8 E 21 itself and B 8 E 41 ). Under similar conditions, the cyclic block copolymer formed larger micelles than the linear triblock but smaller micelles than the linear diblock copolymer. Cyclo-B 8 E 42 and E 21 B 8 E 21 had similar values of the cmc, about 10 times larger than that of B 8 E 41 .