Elastic sheath–liquid crystal core fibres achieved by microfluidic wet spinning

in Journal of Materials Chemistry C (2019)

While coaxial polymer sheath–liquid crystal core fibres attract interest for fundamental research as well as applied reasons, the main method for achieving them so far, electrospinning, is complex and has ... [more ▼]

While coaxial polymer sheath–liquid crystal core fibres attract interest for fundamental research as well as applied reasons, the main method for achieving them so far, electrospinning, is complex and has significant limitations. It has proven particularly challenging to spin fibres with an elastic sheath. As an alternative approach, we present a microfluidic wet spinning process that allows us to produce liquid crystal core–polyisoprene rubber sheath fibres on a laboratory scale. The fibres can be stretched by up to 300% with intact core–sheath geometry. We spin fibres with nematic as well as with cholesteric liquid crystal in the core, the latter turning the composite fibre into an elastic cylindrical photonic crystal. Iridescent colours are easily observable by the naked eye. As this coaxial wet spinning should be amenable to upscaling, this could allow large-scale production of innovative functional fibres, attractive through the various responsive characteristics of different liquid crystal phases being incorporated into an elastic textile fiber form factor. [less ▲]

Nanoparticles dispersed in liquid crystals: impact on conductivity, low-frequency relaxation and electro-optical performance

in Journal of Materials Chemistry C (2016), 4(16), 3485-3491

We study the impact of functionalized gold nanoparticles on the impedance response of nematic nanoparticle/liquid crystal dispersions in the frequency range of 0.1 Hz–100 kHz. By fitting a suitable ... [more ▼]

We study the impact of functionalized gold nanoparticles on the impedance response of nematic nanoparticle/liquid crystal dispersions in the frequency range of 0.1 Hz–100 kHz. By fitting a suitable equivalent electric circuit model to the experimental data we show that nanoparticle doping does not affect the permittivity of the nematic host, but significantly increases its conductivity. This causes a Debye-type relaxation process in the Hz and low kHz regime, which originates from mobile charge carriers accumulating near the electrodes of the test cell. The effect of this electrode polarization on the electro-optical response of the nanocomposites is discussed with respect to threshold voltage and dielectric permittivity. We demonstrate that nanoparticle doping does not alter the electro-optic response at frequencies above the occurrence of electrode polarization, while it strongly deteriorates the performance in the low frequency regime. [less ▲]

Laser annealing of electrodeposited CuInSe2 Semiconductor Precursors: Experiment and Modeling

in Journal of Materials Chemistry C (2016)

Multifunctional responsive fibers produced by dual liquid crystal core electrospinning

in Journal of Materials Chemistry C (2015), 3

We demonstrate that coaxial electrospinning with more than one core channel, each containing a different type of liquid crystal, can be used to produce multifunctional fibers in a one-step process. They ... [more ▼]

We demonstrate that coaxial electrospinning with more than one core channel, each containing a different type of liquid crystal, can be used to produce multifunctional fibers in a one-step process. They respond to more than one stimulus or with multiple threshold values, and the individual cores may feature different physical properties such as iridescent reflection in one core and birefringence in another. In order to ensure good fiber morphology and intact, unmixed and well separated cores, two important precautions must be taken. First, the fibers should not be collected on a hydrophilic substrate, as this will lead to severe fiber deformation and core mixing after collection, as a result of capillary forces from the water that condenses on the fiber during spinning. Second, the addition of surfactants to the polymer solution should be avoided, although it may appear beneficial for the spinning process as it reduces surface tension and increases conductivity. This is because the surfactant enters the liquid crystal core, possibly together with water in the form of inverse micelles, seriously degrading the performance of the liquid crystal. [less ▲]

Tuneable Multicoloured Patterns From Photonic Cross Communication Between Cholesteric Liquid Crystal Droplets

in Journal of Materials Chemistry C (2014), 2(5), 806-810

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N ... [more ▼]

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications. [less ▲]