August 2015

Paper on dual-core liquid crystal electrospinning

Congratulations to YooMee, whose M.Sc. research on the preparation of multiresponsive fibers, by electrospinning dual-core fibers with different liquid crystals next to each other, is now on-line at Journal of Materials Chemistry C. The paper, published in collaboration with Prof. Changsoon Kim at Seoul National University, describes the possibilities opened by incorporating multiple liquid crystals in one and the same fiber, giving a single fiber multiple functions (like selective reflection and birefringence, as in the bottom right pane of the ToC graphic, reproduced here). Apart from the feat of producing the fibers, YooMee gives two messages of great practical importance concerning liquid crystal electrospinning. First, she confirms the recent observation in a paper with DaeKyom as lead author, that electrospun core-sheath fibers must not be collected on hydrophilic substrates like ordinary glass or silicon chips, because then capillary forces from condensed water will deform the fibers. In YooMee's case, she found that the phenomenon even leads to mixing of the adjacent cores. Second, while ionic surfactants are a useful additive to the polymer solution in solid fiber spinning, since they increase the conductivity and reduce the surface tension, they are a bad choice when the fiber contains a liquid crystal core. YooMee found dramatic reductions in clearing point of the encapsulated liquid crystal whenever the polymer sheath solution contained surfactant, indicating that the surfactant actually enters the liquid crystal and disturbs its order. Download her paper at Journal of Materials Chemistry C!