title: Pathways of cylindrical orientations in PS-b-P4VP diblock copolymer thin films upon solvent vapor annealing.
abstract: The orientation changes of perpendicular cylindrical microdomains in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) thin films upon annealing in different solvent vapors were investigated by in situ grazing incidence small-angle X-ray scattering (GISAXS) and ex situ scanning force microscopy (SFM). The swelling of P4VP perpendicular cylinders (C⊥) in chloroform, a non-selective solvent vapor, leads to the reorientation to in-plane cylinders through a disordered state in a particular kinetic pathway in the phase diagram upon drying. On the other hand, the swelling of the P4VP perpendicular cylinders in a selective solvent vapor (i.e., 1,4-dioxane) induces a morphological transition from cylindrical to ellipsoidal as a transient structure to spherical microdomains; subsequent solvent evaporation resulted in shrinkage of the matrix in the vertical direction, merging the ellipsoidal domains into the perpendicularly aligned cylinders. In this paper, we have discussed the mechanism based on the selectivity of the solvent to the constituting blocks that is mainly responsible for the orientation changes.
authors.affiliation: Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum-695 019, Kerala, India. bhojegowd@niist.res.in.
authors.forename: E Bhoje
authors.initials: EB
authors.lastname: Gowd
authors.forename: Tadanori
authors.initials: T
authors.lastname: Koga
authors.forename: Maya K
authors.initials: MK
authors.lastname: Endoh
authors.forename: Kamlesh
authors.initials: K
authors.lastname: Kumar
authors.forename: Manfred
authors.initials: M
authors.lastname: Stamm