I am working on a novel method-solvent vapor permeation (SVP) for facile alignment of self-assembled structures in BCP films with thickness on the millimeter scale. The technique is based on pressure-driven transport of a solvent in the vapor phase through a polymer film, resulting in long-range order and alignment of the BCP interfaces parallel to the vapor flux. This fast-driven process is similar to the alignment induced by imposition of shear or extensional flows on swollen polymer melts. The polymer microstructure is aligned by the relative motion of solvent molecules past the polymer chains. We have successfully verified the idea using a simple setup. (Figure 1) The SAXS data demonstrate the formation of vertically aligned hexagonally packed cylinders on vapor permeation from an initially isotropic SEBS film. (Figure 2) The influence of the controlling parameters including temperature, pressure, flow, solvent, etc. is being explored in detail alongside the expected kinetic, morphological and molecular weight effects.

Figure 1 Schematic illustration of the experimental setup and of alignment of BCP domains via solvent permeation through the polymer film.