Hierarchical Terrace Formation in PS-b-P4VP(PDP) Supramolecular Thin Films

The terrace formation behavior of chloroform vapor annealed thin films of asymmetric, low molecular weight comb-shaped supramolecules consisting of a short polystyrene (PS) block and a long supramolecular block of poly(4-vinylpyridine) (P4VP) hydrogen bonded with pentadecylphenol (PDP) on silicon oxide (SiO2) was examined with atomic force microscopy. During annealing, PS microphase separated from the disordered P4VP(PDP) comb, resulting in the formation of terraces of parallelly oriented microdomains of PS in a matrix of P4VP. Upon evaporation of the solvent, the P4VP(PDP) combs dropped below their order-disorder transition, and formed alternating layers of P4VP and PDP, which for high P4VP(PDP) fractions were also oriented parallel to the substrate. This resulted in terraces of the short P4VP(PDP) length scale within terraces of the PS-P4VP long length scale. Washing away PDP from the thin films with ethanol provided an effective means of studying the morphology of the lowest terrace of the thin films and, for a particular system, also resulted in a uniform monolayer of cylinders with a PS core and a P4VP corona.