X-ray Photon Correlation Spectroscopy of Cylindrical and Lamellar Block Copolymers of Controlled Grain Size.

This work studied structural dynamics of block copolymers as a function of grain size and morphology. The block copolymers studied were cylindrical and lamellar polystyrene-b-poly(ethylene oxide) (PS-b-PEO). This examination is the first of structural dynamics for a cylindrical block polymer using X-ray photon correlation spectroscopy (XPCS). The PS-b-PEO grain size was controlled by solvent vapor annealing. Morphologies and grain sizes were evaluated using small-angle x-ray scattering (SAXS) and atomic force microscopy (AFM). The results of SAXS and AFM showed that the grain size variation depends on which homopolymer formed the matrix majority. Grain size of a PS matrix majority PS-b-PEO increased with high solvent evaporation rate. By contrast, the PEO majority matrix grain size decreased with increasing solvent evaporation rate. Autocorrelation function g₂, structural relaxation time τ_st, and stretching exponent β from XPCS measurements were evaluated as a function of morphologies and grain sizes.