Diblock copolymers of ethylene oxide and 1,2-butylene oxide in aqueous solution

The dependence of log(cmc) on hydrophobic block length n was examined for EmBn copolymers (E = oxyethylene, B = oxybutylene, subscripts denote number-average block lengths in repeat units)with n in the range 30-76. Combination with published data for EmBn diblock copolymers with shorter E-blocks shows two changes of slope in the log(cmc)-n plot corresponding to the onset of unimolecular micelle formation at n approximate to 12 and completion of this process at n approximate to 30. The results are discussed with reference to published data for EmLn and EmCLn (L from D,L-lactide; CL from epsilon-caprolactone) copolymers, which show similar behaviour. (C) 2008 Elsevier B.V. All rights reserved.