Crystallization-induced switching of the morphology of poly(ethylene oxide)-block-polybutadiene micelles

We studied the morphology of micelles formed by a well-defined poly(1,2-butadiene)-block-poly(ethylene oxide) diblock copolymer (PB-b-PEO). Dissolved in n-heptane at 70 °C, that is, above the melting point of PEO, spherical micelles are formed due to the selectivity of the solvent for the PB-block. If the solutions are cooled down to low temperatures, the liquid PEO-block crystallizes within the cores of the spherical micelles that remain stable. If, however, the solutions are quenched to 30 °C, the spherical micelles aggregate to a novel meander-like structure within several minutes. In its final state, the meander-like super-structure is crystalline, as revealed by time-resolved wide-angl…