Phase Behavior of Solvent Vapor Annealed Thin Films of PS-b-P4VP(PDP) Supramolecules

The phase behavior and terrace formation of solvent (chloroform) vapor annealed thin films of asymmetric comb-shaped supramolecules consisting of a polystyrene (PS) block and a supramolecular block of poly(4-vinylpyridine) (P4VP) hydrogen bonded with pentadecylphenol (PDP) on silicon oxide (SiO2) were examined. P4VP(PDP) was found to be present at the SiO2 interface as well as the air interface, implying symmetric boundary conditions. Because of the inherent change in composition by swelling in a selective solvent, the morphology of a lamellar film could be changed to cylindrical by swelling at different vapor pressures of chloroform vapor. Swelling at a specific vapor pressure at the phase boundary between lamellar and cylindrical resulted in noncommon terrace formation behavior. The lowest terrace consisted of two wetting layers forming one lamella, the second terrace contained perpendicular lamellae, and the highest terrace consisted of parallel P4VP(PDP) cylinders. The results are presented in a morphology diagram as a function of film thickness and composition.