Tailoring Pore Structure of Ultralight Electrospun Sponges by Solid Templating

Abstract

Freeze-casted nanofiber based sponges or aerogels exhibit a hierarchical porous structure. Pore formation is only partially understood. Therefore, we studied the underlying solid templating mechanism. We were able to tailor the secondary pore size between 9.5 and 123 µm while retaining the smaller primary pores known from electrospun nanofiber membranes. To understand the effect of microstructure on the sponges' bulk properties, mass flow through the pores and interaction with the sponges' internal surface were investigated. By solely altering the sponges' microstructure we indeed found tunability in permeability by a factor 7 and in filtration efficiency by a factor of 220. Hence, pore architecture of nanofiber based sponges is a key element for their performance. The selected pullulan/PVA polymer blends and aqueous electrospinning conditions are benign and allow the facile adaptation of these ultralight highly porous sponges for a large number of applications.

From Short Electrospun Nanofibers to Ultralight Aerogels with Tunable Pore Structure

“…shock freezing) will preserve the isotropic distribution of the short nanofibers from the starting dispersion, so that crystal templating is minimized. [12] Depending on v f , on the fiber loading of the dispersion, and on the choice of solvent, pore size and structure can be governed, to tailor the macroscopic properties of the aerogel. [12,13b,14a,b] For instance using a directional freezing approach, it other polymers (Table 1).…”

“…At the same time it was possible to lower aerosol penetration from 9.98 to 0.04% by altering the aerogels' microstructure to enhance the filtration efficiency by more than two orders of magnitude. [12] Perspectives After a promising start, solid templating of electrospun materials may become established as a new process to generate tailor-made 3D structures for three reasons: first, the process is simple and straightforward. Liquid handling of fibrous dispersions is scalable and, most importantly, independent from the fiber formation process by electrospinning.…”

“…Understanding the underlying solid templating mechanism allowed us to tailor pore shape and pore size of nanofiber-based aerogels. [12] Combining a controllable shaping method with the versatility of fiber production by electrospinning proves outstanding potential for nanofiber-based scaffold production. In the following, we will highlight the fundamental processing steps and applications of 3D nanofiber-based aerogels according to recent advances in this young field of research.…”

“…2). First, continuous nanofibers are (PAN), [2a,b,13a,e-g] polylactic acid (PLA) [13i,j] or polycaprolactone (PCL), [13h] but there are also composites reported from biopolymers or even from inorganic sources, such as gelatin, [13i,j] pullulan, [12] or SiO 2 . [13b,c] …”

Low Density, Thermally Stable, and Intrinsic Flame Retardant Poly(bis(benzimidazo)Benzophenanthroline‐dione) Sponge

“…Series of electrospun polymer nanofibers including polyacrylonitrile, polyimide (PI), and polyacrylate‐based polymer has been used to assemble mechanical stable 3D sponges with numerous applications. Biodegradable polymer sponges, poly(lactic acid), polycaprolactone, and poly(vinyl alcohol) (PVA), were also prepared using similar approach, which showed applications in tissue engineering. However, these polymer‐based sponges have the common drawback of poor thermal properties which limits their application in high temperature areas.…”