Temperature dependences of the critical micelle concentrations of diblock oxyethylene/oxybutylene copolymers. A case of athermal micellization

The athermal micellization of the diblock oxyethylene/oxybutylene (E/B) copolymers was examined. The low standard enthalpy changes associated with the units of lengthy B blocks are attributed to the blocks being tightly coiled in the dispersed molecular standard state, so that interaction with H2O is minimized. An unassociated copolymer with its hydrophobic block in such a tightly coiled state is called a `monomolecular micelle'. The transfer of B blocks to the micelle core involves little or no standard enthalpy change. The transfer of E blocks from the solution to a more concentrated state in the micelle fringe results in a small enthalpy change.