Lateral Ordering of Cylindrical Microdomains Under Solvent Vapor

The development of the morphology in asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) thin films in tetrahydrofuran (THF) vapor, a selective solvent for majority PS block, as a function of time was investigated by scanning force microscopy (SFM) and grazing incidence small-angle X-ray scattering (GISAXS). When the PS-b-P4VP films were spin-coated from a toluene/THF mixture onto a silicon substrate, cylindrical microdomains were found to be oriented normal to the surface. By annealing under the THF solvent vapor, the distribution of the size and center-to-center distance between the cylindrical microdomains were significantly narrowed. The orientation and grain size of the cylindrical microdomains in the annealed films were characterized Using Moire analysis obtained from SFM scan. GISAXS was used to characterize the morphology of the entire film.