Solvent vapor annealing: an efficient approach for inscribing secondary nanostructures onto electrospun fibers

Solvent vapor annealing (SVA) is originally developed to attain equilibrium nanostructures from microphase-separated block polymer thin films. Interestingly, by carefully choosing a solvent vapor that can selectively mobilize the amorphous chains of a semicrystalline polymer while preserving the integrity of its crystalline structure, this study demonstrates that the SVA method can also be utilized to introduce hierarchical structures onto semicrystalline polymer-based materials. This study on electrospun poly(ε-caprolactone) (PCL) fibers clearly shows that acetone, a poor solvent for PCL, can effectively delocalize the amorphous chains and redeposit them onto the pre-existing crystal edges, giving rise to secondary nanostructures inscribed onto the PCL fibers. In the past decade, various fiber fabrication methods and numerous fiber products are reported. The easy one-step approach reported here provides new insight into the design and fabrication of structurally hierarchical polymeric materials.