Polymer nanofibers by controllable infiltration of vapour swollen polymers into cylindrical nanopores

We report on a new method for the fabrication of polymer nanofibers based on wetting of cylindrical alumina nanopores with solvent vapour swollen polymers. Solvent annealing is used to swell and soften polymers at room temperature, so that they are allowed to infiltrate into cylindrical nanopores by capillary force. The method of swelling assisted infiltration is capable of eliminating the problem of thermal degradation from the widely used melt wetting; in addition, the thus formed nanofibers display well aligned one-dimensional structures and controllable aspect ratios, in contrast to those from solution wetting, the morphologies of which are difficult to be controlled. By using the proposed method, several homopolymers including thermo-sensitive polyvinyl chloride (PVC) and conducting poly(3-hexylthiophene) (P3HT) were found to form nanofibers with high aspect ratios. In particular, we have studied the microphase separation behaviour of vapour swollen block copolymers (BCPs) under cylindrical confinement, and found that the intrinsic ordered pattern of BCPs (i.e., in the melt state) would transform into a different structure due to solvent swelling under cylindrical confinement.