Micellar Aggregates of Amylose-block-polystyrene Rod−Coil Block Copolymers in Water and THF

Amylose- block -polystyrenes with various block copolymer compositions were investigated in water and in THF solution. Fluorescence correlation spectroscopy, dynamic light scattering (DLS), and asymmetric flow field-flow fractionation with multiangle light scattering detection indicate the presence of unimers, oligomers, and large micellar species in THF. Up to four different species were detectable by DLS with hydrodynamic radii ranging from a few nanometers to >10 μm, indicating that the system is not in a thermodynamic equilibrium state. Collapsed aggregates were monitored on a silicon surface by scanning force microscopy and transmission electron microscopy. In water, crew-cut micelles were obtained from the same block copolymers by a single solvent approach, using elevated temperature and pressure. These crew-cut aggregates are much more uniform than the respective star aggregates in THF, and their radii scale with R h ∝ N core 1/4, R h ∝ N corona 1/6 in solution and with R ∝ N core 1/4, R ∝ N corona 1/2 on a silicon surface.