Spinning Functional Fibers: An Interplay of Rheology, Miscibility & Crosslinking

Wearable technology in general has increasingly gained interest in the last few decades and textile with incorporated functional component constitute one form of it. There are multiple ways to produce polymer fibers on both laboratory and industrial scales, and one of them is core–sheath electrospinning, which is a powerful method for producing advanced composite fibers. Liquid crystals (LCs), are materials that readily exhibit optical response to fluctua- tions and change in their immediate environment. By incorporating LC within polymer fibers through electrospinning, it is possible to create responsive LC-polymer fiber mats. However, incorporating a functional core has proven challenging for certain combinations of materials. This thesis explores and addresses some of the concerns involved in the coaxial electrospinning of fibers incorporating LCs from several standpoints.
Firstly, the effect of solvents on the electrospinning process was systematically studied. Fol- lowing this, an optimum viscosity with pure and mixed solvents for successful electrospinning was identified and uniform fibers with different solvent combinations was produced. Using the knowledge gained, core-sheath electrospinning with LC as the core was carried out. One of the key findings of this work, the identification of a suitable means to reduce the interfacial tension between the core and sheath fluid to prevent break up of the jet and produce uniformly filled fibers, while at the same time avoiding complete mixing between core and sheath. These findings can be applied to any combination of core and sheath materials and should appeal to a large community of researchers.
Eventually, to achieve the durability of the LC-functionalized electrospun fiber mats for use in wearable technology, the sheath polymer of the fiber were crosslinked after spinning. The resultant crosslinked fibers were easily manipulated by hand and even fully immersed in water without dissolving and without losing their functional LC core.