Liquid crystalline photoactuators typically bend toward the light source, driven by the isomerization of azobenzene. In samples with a relatively large thickness and high azobenzene loading such as LC photoactuators, intense optical beams are seen to be absorbed in spatially nonexponential ways. Here we show that the dynamics of the related mechanical behavior is also strongly nonlinear, where the actuator reaches a maximum bend before unbending again to its equilibrium deformed state. The effect is amplified when combined with actuators with an internal composition gradient, leading to a reversal of the bending direction away from the light source.

A printable H-bonded cholesteric liquid crystal (CLC) polymer film has been fabricated that, after conversion to a hygroscopic polymer salt film, responds to temperature and humidity by changing its reflection color. Fast-responding humidity sensors have been made in which the reflection color changes between green and yellow depending on the relative humidity. The change in reflection band is a result of a change in helix pitch in the film due to absorption and desorption of water, resulting in swelling/deswelling of the film material. When the polymer salt was saturated with water, a red-reflecting film was obtained that can potentially act as a time/temperature integrator. Finally, the films were printed on a foil, showing the potential application of supramolecular CLC materials as low-cost, printable, battery-free optical sensors.

An optical and irreversible temperature sensor (e.g., a time-temperature integrator) is reported based on a mechanically embossed chiral-nematic polymer network. The polymer consists of a chemical and a physical (hydrogenbonded) network and has a refl ection band in the visible wavelength range. The sensors are produced by mechanical embossing at elevated temperatures. A relative large compressive deformation (up to 10%) is obtained inducing a shift to shorter wavelength of the refl ection band ( > 30 nm). After embossing, a temperature sensor is obtained that exhibits an irreversible optical response. A permanent color shift to longer wavelengths (red) is observed upon heating of the polymer material to temperatures above the glass transition temperature. It is illustrated that the observed permanent color shift is related to shape memory in the polymer material. The fi lms can be printed on a foil, thus showing that these sensors are potentially interesting as time-temperature integrators for applications in food and pharmaceutical products.

<p>Carbohydrates are important feed stocks in synthesis of natural products and so attract the interest of many organic researchers throughout the world, most notably in the last 10 years. The work described within explores the manipulation of the glucose-derived glucal. The addition of a reactive substituted cyclopropane across the alkene has been employed synthetically for many years, the subsequent ring breaking/expansion has been identified in the lab as slow and needing the support of catalysts. We ask the question, “Will cyclopropanated carbohydrates undergo the slow ring breaking/expansion in the presence of proteins, and are we able to identify which of the two types of mechanisms the reaction is going through?” The cyclopropane will act as a warhead to bind to proteins through Ferrier like rearrangements, resulting in irreversible inhibition. To identify the potential of such compounds, a combination of techniques are used to identify potential pathways, protein targets and reactivity through structure activity relationships.  The key steps involved in finding out the potential of cyclopropanated carbohydrates are to determine biological activities through bio-assays, structure activity relationships, selective binding, chemical genetics and chemical proteomics. The bio-assays together with structure activity relationships provides evidence on which chemical mechanism is occurring when the biological target is interacting with the bioactive cyclopropanated carbohydrates. The most active compound, benzose (7), was subjected to chemical genetic analysis to determine the pathways and processes that are involved with the mode of action. The chemical genetic analysis was complimented by chemical proteomics to identify the direct biological target. Analogues of benzose were synthesised by the addition of azide groups to undergo a Huisgen Cyclisation within a cell lysate to facilitate binding to an alkyne-substituted matrix.</p>