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

摘要

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 mum,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 propor.to N_(core)~(1/4),R_h propor.to N_(corona)~(1/6)in solution and with R propor.to N_(core)~(1/4),R propor.to N_(corona)~(1/2)on a silicon surface.