Amphiphilic Nanofiber‐Based Aerogels for Selective Liquid Absorption from Electrospun Biopolymers

Abstract

COMMUNICATION (1 of 7)often suffer from poor mechanical stability, [10] the scientific resources devoted to developing electrospun 3D materials are increasing each year. [6b] The unique properties of 3D materials from electrospun nanofibers enable their application as scaffolds in tissue engineering, [11] framework for heterogeneous catalysis, [12] drug release composites, [11c,13] personal safety equipment, [14] sensors, [15] or electrodes. [16] It has been shown recently, that colloidal dispersions of short electrospun nanofibers prepared by cutting electrospun membranes open a complementary and controlled approach in nonwoven nanofiber processing. [17] This change in paradigm-to separate fiber formation and fiber processing-elegantly overcomes the main drawback of electrospinning, since fiber processing is no longer coupled to the intrinsically lamellar fiber deposition, but separated into more versatile liquid handling process. Using short electrospun nanofiber dispersions, Ding and co-workers [5a] and Greiner and co-workers [18] pioneered the preparation of ultralight 3D aerogels or sponges by freeze casting. These nanofiberbased 3D materials are either referred to as aerogels [5a] or sponges. [18] They show high porosities like silica-based aerogels, but the solid scaffold is preformed by short nanofibers. [19] OurThe ORCID identification number(s) for the author(s) of this article can be found under http://dx.doi.org/10.1002/admi.201700065. Water PurificationElectrospinning allows the fabrication of nanofibers from biopolymers, synthetic polymers, and even metals. In terms of applications electrospinning has outperformed alternative technologies for nanofiber production such as melt blowing, [1] selfassembly, [2] phase separation, [3] solution blow spinning, [4] and nanofiber drawing. [3a] Electrospun nanofibers feature a large specific surface area, ultrahigh aspect ratio, extreme flexibility, and the electrospinning process can easily be scaled up. One limitation in electrospinning is the anisotropic lamellar deposition character due to the layer-by-layer manufacturing process. [5] Different ways to fabricate porous 3D structures from electrospun nanofibers have been exploited, [6] such as self-assembly, [7] cool drum spinning, [8] or gas expansion. [9] Even though those 3D scaffolds lack the possibility to add scalable pores and

Cellulose Silica Hybrid Nanofiber Aerogels: From Sol–Gel Electrospun Nanofibers to Multifunctional Aerogels

“…Furthermore hybrid NFA‐therm exhibit fatigue residency after 50 stress–strain cycles at 40% strain (Figure E) and after 10 cycles at various other strains (Figure S6A–C, Supporting Information)–a characteristic that can be attributed to the strong fibrous structure of the cell walls which act as a cushion when compressed and bounce back to their original position after the load is lifted . A relatively high stress value in the first cycles during each fatigue test can be attributed to the friction between adjacent fibers.…”

“…In order to strengthen the network, we thermally treated CDA‐only and as‐prepared hybrid NFA. Although most of the previously conducted research involves chemical crosslinkers to strengthen the structure of conventional aerogels or NFA, our rationale to use thermal treatment was to maintain the sustainable nature of the process and also enhance possibilities of interactions between sol–gel processed silica and CDA network in a simple way. Upon thermal treatment, hybrid‐NFA display remarkable retention in their 3D (Figure E) structure with about 4.1% rise in density and 0.3% loss in porosity (Table S1, Supporting Information), while CDA‐NFA completely collapse in structure generating a solid mass with complete loss in 3D orientation (Figure F).…”

Biopolymer Aerogels and Foams: Chemistry, Properties, and Applications

“…Flexible, hydrophobic freeze‐dried foams and supercritically dried, superinsulating aerogels were synthesized from NFC suspensions mixed with methyltrimethoxysilane. Chemical vapor deposition of octyltrichlorosilane has also been used to hydrophobize cellulose and pullulane aerogels and foams (Figure ) for oil–water separation (Figure c). The trifunctional silanes discussed above tend to self‐polymerize through ≡Si‐O‐Si≡ cross‐linking and form larger polysiloxane structures or layers on the biopolymer surface, thereby leading to a strong adhesion of the polysiloxane phase to the biopolymer through multiple covalent bonds and hydrogen bonding as well as dipole–dipole and van der Waals interactions.…”

“…c) Fast and selective uptake of chloroform (red) from water. Reproduced with permission . Copyright 2017, Wiley.…”

Biopolymer‐Aerogele und ‐Schäume: Chemie, Eigenschaften und Anwendungen

“…Biopolymer‐Aerogele sind auch aus Carrageen, Agar, Xanthan, Guar und Pullulan synthetisiert worden. Alle diese Polysaccharide haben spezifische Molekülstrukturen, die zu verschiedenen Gelbildungsmechanismen und Gel‐ und Aerogeleigenschaften führen.…”