Liquid crystal device

The invention relates to a device comprising at least one substrate, an electrode structure and a liquid crystalline polymer film obtainable from a polymerisable LC medium comprising one or more multi-or direactive or monoreactive mesogenic compounds, characterized in that the surface shape of said polymer film can be electrically switched. Furthermore, the invention relates to a process of production of said device, to the use of said device in an electro-opticalor electro-mechanical device and to an electro-opticalor electro-mechanical device comprising said device

Liquid crystal device

The invention relates to a device comprising at least one substrate, an electrode structure and a liquid crystalline polymer film obtainable from a polymerisable LC medium comprising one or more multi-or direactive or monoreactive mesogenic compounds, characterized in that the surface shape of said polymer film can be electrically switched. Furthermore, the invention relates to a process of production of said device, to the use of said device in an electro-opticalor electro-mechanical device and to an electro-opticalor electro-mechanical device comprising said device

Stimuli-responsive polymer film or coating prepared by mixing in a suitable fashion a side chain liquid crystalline polymer with reactive mesogens and responsive devices:process for preparing the same

The limitation of the different classes of responsive liquid crystals such as volatility in case of low molecular weight liquid crystals (LMWLCs) can be overcome by the development of a responsive film based on polymerliquid crystals (PLCs) and reactive mesogens (RMs or reactive liquid crystal monomers) to create a responsive film or coating material which appears to be easily alignable and processable. That coating material shows a large response of which the properties can be tuned in a modular approach. In this way, the advantages of both materials, PLCs and RMs, were combined, yielding stable films, which can be aligned when desired and which stimuli- responsive properties can be tuned by the choice of RMs. Thus mixtures of PLCs with RMs open the doors to a wide variety of stimuli-responsive coating systems, without the need of time consuming trial-and-error synthesis of PLCs and closed liquid crystal cells. By choosing chiral RMs, cholesteric LC coatings can for instance be fabricated, while a light responsive RM could provide a light responsive coating. In addition, one could use similar methods as were used for LMWLCs with RMs in closed cells to prepare for example broadband reflectors or patterned coatings that change topography by a stimulus

Photo-controlled diffusion in reacting liquid crystals : a new tool for the creation of complex molecular architectures

Diffusion enforced photo-assembling during polymerization of a chiral­nematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross-section of the film. The polarization selective reflection band of cholesterics can be made much wider than those of single pitch materials and may expand over the whole visible wavelength. The paper discusses the photo-controlled diffusion process in thin films, the important process parameters and some ofthe properties of the molecular architectures obtained

Nano-textured polymers for future architectural needs

The rapid developments in molecular sciences like nanotechnology and self-organizing molecular systems generate a wealth of new materials and functions. In comparison to electronics the application in architecture remains somewhat underexposed. New functionalities in optics, responsive mechanics, sensing and adjustable permeation for gases and water might add to new opportunities in providing for personal comfort and energy management in houses and professional buildings. With a number of examples we demonstrate how complex but well-controlled molecular architectures provide functionalities worthwhile of being integrated in architectural designs. Optical coatings are capable of switching colors or reflectivity, creating possibilities for design but also for the control of thermal transmission through windows. They respond to temperature, light intensity, or both. Selectively-reflective thin polymer layers or paint pigments can be designed to switch between infrared and visible regions of the solar spectrum. Coatings can be designed to change their topology and thereby their appearance, of interest for in-house light management, or just for aesthetic appeal. Plastic materials can be imbued with the property of autonomous sun tracking and provided morphing behavior upon contact with moisture or exposure to light. Many of these materials need further developments to meet the requirements for building integration with respect to robustness, lifetime, and the like, which will only be accomplished after demonstration of interest from the architectural world

Artificial flagella: bio-inspired responsive polymers for micro-object manipulation

No abstract

Anisotropic light emissions in luminescent solar concentrators-isotropic systems

In this paper we develop a model to describe the emission profile from randomly oriented dichroic dye molecules in a luminescent solar concentrator (LSC) waveguide as a function of incoming light direction. The resulting emission is non-isotropic, in contradiction to what is used in almost all previous simulations on the performance of LSCs, and helps explain the large surface losses measured in these devices. To achieve more precise LSC performance simulations we suggest that the dichroic nature of the dyes must be included in the future modeling efforts

Simulations with a dynamic reaction-diffusion model of the polymer grating preparation by patterned ultraviolet illumination

Simulations of volume fraction profiles formed during the lithographic preparation of polymer gratings are made with a reaction/diffusion model, based on the Flory–Huggins theory. Monomer migration is driven by a gradient in the chemical potential rather than a gradient in the concentration. If the chemical potential is used as the driving force, monomer migration is not only driven by a difference in concentration, or volume fraction, but also by other entropic effects: the differences in monomer length and the degree of crosslinking of a polymer network. The monomer volume fractions are simulated as a function of position for different ultraviolet intensities and various grating pitches. Profound edges of the monomer volume fractions caused by the fact that the reaction rate is high compared to the diffusion rate are both measured and simulated. An excellent agreement with nuclear microprobe measurements on the polymer gratings is obtaine

Photonic time-temperature sensor having an embossed interpenetrating network of cholesteric liquid crystalline polymers and a secondary polymer

Photonic time-temperature sensor consisting of an embossed interpenetrating network of a cholesteric liquid crystalline polymers and a secondary polymer. Preferably in which the secondary polymer is orthogonal and is not covalently attached to the interpenetrating network, but physically interpenetrated therein. For use as food sensor for checking freshness of the food

Increased efficiency of luminescent solar concentrators after application of organic wavelength selective mirrors

Organic wavelength-selective mirrors are used to reduce the loss of emitted photons through the surface of a luminescent solar concentrator (LSC). A theoretical calculation suggests that application of a 400 nm broad reflector on top of an LSC containing BASF Lumogen Red 305 as a luminophore can reflect 91% of all surface emitted photons back into the device. Used in this way, such broad reflectors could increase the edge-emission efficiency of the LSC by up to 66%. Similarly, 175 nm broad reflectors could increase efficiency up to 45%. Measurements demonstrate more limited effectiveness and dependency on the peak absorbance of the LSC. At higher absorbance, the increased number of internal re-absorption events reduces the effectiveness of the reflectors, leading to a maximum increase in LSC efficiency of ~5% for an LSC with a peak absorbance of 1. Reducing re-absorption by reducing dye concentration or the coverage of the luminophore coating results in an increase in LSC efficiency of up to 30% and 27%, respectively