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The mechanical properties of liquid crystal elastomers (LCEs) make them suitable candidates for pressure-sensitive adhesives (PSAs). Using the nematic dumbbell constitutive model, and the block model of PSAs, we study their tack energy and the debonding process as could be measured experimentally in the probe-tack test. To investigate their performance as switchable PSAs we compare the tack energy for the director aligned parallel, and perpendicular to the substrate normal, and for the isotropic state. We find that the tack energy is larger in the parallel alignment than the isotropic case by over a factor of two. The tack energy for the perpendicular alignment can be 50% less than the isotropic case. We propose a mechanism for reversibly switchable adhesion based on the reversibility of the isotropic to nematic transition. Finally we consider the influence of several material parameters that could be used to tune the stress-strain response.

The helical-flexo-electro-optic effect shows interesting in-plane electro-optic switching behaviour due to flexoelectric coupling with applied electric fields. Previous understanding of the behaviour has been generally based on an analytic approach which makes certain assumptions about the uniformity of the helical structure and the induced tilt angle under field application. Here we remove these assumptions and develop a perturbative approximation to describe the structure in more detail. We also use a numerical method to investigate the behaviour in regimes where the perturbative approach is inappropriate. The impact of variation in elastic constants and dielectric anisotropy is investigated. We find that dielectric behaviour in particular can lead to substantial differences between the tilt angle obtained here and those obtained using previous analytic models.

We examine how intense optical beams can penetrate deeply into highly absorbing media by a non-linear, photo-bleaching process. The role of stimulated recovery to the dye ground state can be important and is delineated. This analysis of non-linear absorption processes is applicable in general to situations where chromophores are irradiated, for instance in biology. We examine the implications for the bending of cantilevers made of heavily dye-loaded nematic photo-solids, that is nematic glasses and elastomers that have large mechanical reactions to light. In particular we describe the bending of cantilevers sufficiently absorbing that they would not bend if Beer's Law were applicable. We quantify the role of optically-generated heat in determining the mechanical response and conclude that in general it is minor in importance compared with optical effects.

On traversing materials with absorbing dyes, weak optical beams develop a Beer (exponential) profile, while intense beams develop a spatially initially linear and then finally an exponential profile. This anomalous, deep penetration due to photo-bleaching of surface layers is important for heavy dye-loading and intense beams, for instance in photo-actuation. We address the problem of the evolution in time from initial Beer's Law to deeply penetrating optical profiles in dyes. Our solution of the coupled, non-linear, partial differential equations governing the spatio-temporal decay of the Poynting flux and the non-linear dynamics of the \textit{trans-cis} conversion is applicable to general systems of photo-active molecules under intense irradiation, for instance in biology, in spectroscopy and in opto-mechanical devices.

Vertically aligned mono-domain nematic liquid crystal elastomers contract when heated. If a temperature gradient is applied across the width of such a cantilever, inhomogeneous strain distribution leads to bending motion. We modelled the kinetics of thermally-induced bending in the limit of a long thin strip and the predicted time-variation of curvature agreed quantitatively with experimental data from samples with a range of critical indices and nematic-isotropic transition temperatures. We also deduced a value for the thermal diffusion coefficient of the elastomer.