Direct Observation On Spin-Coating Process Of Ps-B-P2vp Thin Films

We studied the structural development of symmetric poly(styrene-b-2-vinylpyridine) (PS-b-P2VP)block copolymers during spin-coating using in situ grazing incidence small-angle X-ray scattering (GISAXS) measurements. During the spin-coating process, after the formation of the micelles in dilute solution,, the selective solvent-induced two kinds of the morphological transition. First, the disordered spherical micelles were transformed into a BCC lattice of spheres, of which the (110) plane was oriented perpendicularly to the subtrate surface. Second, further evaporation induced a transition from spheres on the BCC lattice into cylindrical structures. The orientation of the cylinders perpendicular to the substrate surface was induced by solvent convection perpendicular to the substrate, which occurs during rapid solvent evaporation. After this transition, vitrification of PS and P2VP prevented any further transition from cylinders to the more thermodynamically stable lamellar structures, as are generally observed as the bulk equilibrium state.