Liquid crystal functionalization of electrospun polymer fibers

Abstract

ABSTRACT:A recently introduced new branch of applied polymer science is the production of highly functional and responsive fiber mats by means of electrospinning polymers that include liquid crystals. The liquid crystal, which provides the responsiveness, is most often contained inside fibers of core-sheath geometry, produced via coaxial electrospinning, but it may also be inherent to the polymer itself, for example, in case of liquid crystal elastomers. The first experiments served as proof of concept and to elucidate the basic behavior of the liquid crystal in the fibers, and the field is now ripe for more applied research targeting novel devices, in particular in the realm of wearable technology. In this perspective, we provide a bird's eye view of the current state of the art of liquid crystal electrospinning, as well as of some relevant recent developments in the general electrospinning and liquid crystal research areas, allowing us to sketch a picture of where this young research field and its applications may be heading in the next few years.

Multifunctional responsive fibers produced by dual liquid crystal core electrospinning

“…2. Such a combination could be useful in developing a fiber that simultaneously detects gas exposure, via its nematic core, 14 and senses tensile strain (via a color change of the cholesteric due to the shrinkage of the cross section upon fiber stretching, combined with the dependence of color on confinement 23,24 ). During spinning, the shear flow unwound the helical arrangement that gives rise to the reflection color of the cholesteric, hence this mixture appears grey in the Taylor cone, as seen in the photo in panel (a) of the figure.…”

“…Relying on an electric field to draw a thin jet out of a droplet of spinning solution protruding from a spinneret, [9][10][11][12][13] it is a low-cost, small-footprint spinning technology that is highly versatile and capable of producing core-sheath fibers that are exceptionally thin and that can carry a variety of functionalities, depending on the combination of core and sheath materials. [14][15][16][17][18][19] For instance, the impressive range of stimulus-response relations made possible by liquid crystalline self-assembly, uniquely combining fluidity with long-range order, 20 can be introduced into fibers by coaxial electrospinning with different liquid crystals as core materials. 14 In some cases it is even possible to electrospin liquid crystal-functionalized fibers from a uniform jet, relying on solvent evaporation-induced phase separation for in situ formation of the core-sheath structure.…”

“…[14][15][16][17][18][19] For instance, the impressive range of stimulus-response relations made possible by liquid crystalline self-assembly, uniquely combining fluidity with long-range order, 20 can be introduced into fibers by coaxial electrospinning with different liquid crystals as core materials. 14 In some cases it is even possible to electrospin liquid crystal-functionalized fibers from a uniform jet, relying on solvent evaporation-induced phase separation for in situ formation of the core-sheath structure. 21 A non-woven fiber mat can thus acquire e.g.…”

Non-electronic gas sensors from electrospun mats of liquid crystal core fibres for detecting volatile organic compounds at room temperature

“…The relevance is even greater in specialised communities with military personnel and people working in advanced research or industrial production facilities. Thus, it is hardly a surprise that much research is devoted to identifying alternatives and improvements on the existing range of sensors [4,11,12], aiming to make sensors and detectors inexpensive, reliable and versatile.…”

“…The response is due to the ability of certain gas molecules, even at low concentration, to strongly influence the liquid crystal self-assembly [40,[42][43][44][45], triggering a reorientation of the liquid crystal director [32,34,43,44], a change in period of the supramolecular helix of shortpitch cholesterics [19,36,42,[46][47][48], or even complete loss of long-range ordering [11]. In particular, Abbott and his group [35,39,[43][44][45] demonstrated the capability of nematic LCs as sensors for detecting nerve agents at concentrations as low as part per billion.…”