Solvent Vapor Annealing: An Efficient Approach for Inscribing Secondary Nanostructures onto Electrospun Fibers

Abstract

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.

Hierarchical electrospun nanofibers treated by solvent vapor annealing as air filtration mat for high-efficiency PM2.5 capture

“…3. In addition, ity after SVA treatment [45,46]. It is important to note that PCL crystallite growth is apparently restricted by the PEO phase with a rigid and more densely packed semicrystalline structure.…”

“…PCL/PEO nanofiber mats were fabricated via an improved electrospinning method. In brief, 0.21 g of PEO powder and 0.5 g of PCL pellets were dissolved in 6.3 mL of chloroform solution and then stirred for 24 h at room temperature to obtain a uniform and transparent spinning precursor solution [45]. Next, the solution was allowed to stand for 1 h to drive the air bubbles out of the solution.…”

“…The PCL/PEO fibers that were SVA-treated exhibited clear lamella-like petals. The acetone vapor appeared to first selectively diffuse into the amorphous region because the chain packing in the crystallization zone was loose in the amorphous region, and many lamella-like petals grew on the annealed PCL/PEO nanofibers due to those amorphous chains with low availability and low mobility, which can cause rearrangement during annealing [45]. First, the acetone vapor selectively mobilized kinetically stagnant amorphous chains as the liquid jet quickly dried.…”

“…In this study, the motivation behind SVA treatment of electrospun mats originated primarily from the modification and regulation of micro/nanos-tructures of membranes for potential incremental improvement of filter efficiency. In the current SVA process that is used to fabricate PCL/PEO materials, acetone, as a poor solvent for PCL/PEO nanofibers, can delocalize the amorphous chains very efficiently and allow them to be redeposited onto the preexisting crystal edges, growing nanowrinkled nanostructures on the surface of the PCL/ PEO nanofibers [42][43][44][45]. The fabricated SVA-treated air filtration mat demonstrated a high PM2.5 removal efficiency due to nanowrinkled nanostructures, low resistance to air flow, and light weight.…”

Visualizing the Inner Architecture of Poly(ϵ‐caprolactone)‐Based Biomaterials and Its Impact on Performance Optimization

“…[9,12] The solution containing 10 wt% PCL (or 8:2 by mass PCL/ m-iBuPOSS) was pumped through an 18-gauge syringe needle at a constant rate of 1 mL Á h À1 with a syringe pump (New Era, NE-300 series, Farmingdale, NY). A critical high voltage of 15-20 kV was used to generate an electrically charged solution jet.…”