Combining responsiveness and durability in liquid crystal-functionalised electrospun fibres with crosslinked sheath

Responsive functional composite fibre mats that are mechanically stable and impervious to water exposure are produced by coaxial electrospinning of thermotropic liquid crystal (LC) core inside a water-based solution of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) forming the sheath. Because thermotropic LCs usually cannot be spun inside water-based solutions due to excessive interfacial tension (Formula presented.), a n enabling step is the addition of ethanol or dioxane to the LC as a co-solvent compatible with both core and sheath fluids. This reduces (Formula presented.) sufficiently that coaxial jet spinning is possible. After spinning, thermal cross-linking of the PVA+PAA sheath yields LC-functionalised fibres that can be manipulated by hand and remain intact even upon full immersion in water. The LC core retains its behaviour, nematics showing well-aligned birefringence and transitioning to isotropic upon heating above the clearing point, and cholesterics showing selective reflection which is even enhanced upon water immersion due to the removal of sheath scattering. Our results pave the way to producing LC-functionalised responsive fibre mats using durable polymer sheaths, thereby enabling numerous innovative applications in wearable technology, and they also open new opportunities to study LCs in confinement, without visible impact of the container walls

Molecular model for de-Vries-type smectic A-smectic C phase transition in liquid crystals

We develop both phenomenological and molecular-statistical theory of smectic-A–smectic-C phase transition with anomalously weak smectic layer contraction. Using a general mean-field molecular model, we demonstrate that a relatively simple interaction potential suffices to describe the transition both in conventional and de Vries type smectics. The theoretical results are in excellent agreement with experimental data. The approach can be used to describe tilting transitions in other soft matter systems