A temperature-responsive near-infrared reflective coating was fabricated based on a side-chain liquid crystal siloxane polymer using a simple wired-bar method. The cholesteric liquid crystalline polymer film showed a blue shift of the reflection band of ∼1000 nm in the IR region upon heating. The temperature-responsive change of the reflection band was reversible. Compared to that of the same mixture system in an alignment cell, the coating showed a significantly faster response. This research demonstrates an easy way to prepare a temperature-responsive IR-reflective coating that shifts its reflection to a shorter wavelength upon heating. As IR radiation of shorter wavelengths is more strongly represented in sunlight than longer wavelengths, this coating could be used to selectively reduce heating of an indoor space when the temperature is high. This is promising for the future application of smart climate control.
Thermosensitive polymers show an entropy-driven transition from a well-solvated to a poorly solvated polymer chain, resulting in a more compact globular conformation. The transition at the lower critical solution temperature (LCST) is often sharp, which allows for a wide range of smart material applications. At the LCST, oligo(ethylene glycol)-substituted polyisocyanides (PICs) form soft hydrogels, composed of polymer bundles similar to biological gels, such as actin, fibrin and intermediate filaments. Here, we show that the LCST of PICs strongly depends linearly on the length of the ethylene glycol (EG) tails; every EG group increases the LCST and thus the gelation temperature by nearly 30 °C. Using a copolymerisation approach, we demonstrate that we can precisely tailor the gelation temperature between 10 °C and 60 °C and, consequently, tune the mechanical properties of the PIC gels.
The type of glazing implemented in a building plays an important role in the heat management of a building. Solar heat entering through glazing causes overheating of interior spaces and increases building’s cooling load. In this work, the energy saving potential of window films based on Cholesteric Liquid Crystals (CLC) is explored. This emerging technology allows for the fabrication of static and thermochromic solar heat rejecting window films and can provide a simple renovation solution towards energy efficient buildings. Simulations on a model office showed that static CLC-based window films can save up to 29% on a building’s annual energy use in warm climates. In climates with distinct summer and winter seasons, static solar heat rejecting windows films cause an additional heating demand during winters, which reduces the annual energy savings. In these climates, the benefit of thermochromic CLC-based window films becomes evident and an annual energy saving up to 22% can be achieved.
Directing the spatial organization of functional supramolecular and polymeric materials at larger length scales is essential for many biological and molecular optoelectronic applications. Although the application of electrical fields is one of the most powerful approaches to induce spatial control, it is rarely applied experimentally in aqueous solutions, since the low susceptibility of soft and biological materials requires the use of high fields, which leads to parasitic heating and electrochemical degradation. In this work, we demonstrate that we can apply electric fields when we use a mineral liquid crystal as a responsive template. Besides aligning and positioning functional soft matter, we show that the concentration of the liquid crystal template controls the morphology of the assembly. As our setup is very easy to operate and our approach lacks specific molecular interactions, we believe it will be applicable for a wide range of (aqueous) materials.
9009wileyonlinelibrary.com to liquid crystals or materials generated under the influence of a strong external stimulus. [5][6][7] These techniques, amongst others, include photolithography [8,9] and soft lithography, [9,10] the applications of electric fields [11,12] and shear flow alignment. [13,14] An interesting approach to reduce the required fields strengths is liquid crystal templating, that allows to organize soft, self-assembling materials in (aqueous) liquid crystals and use external stimuli to exert spatial control. [15][16][17][18] In all these approaches, including liquid crystal templating, the molecular concentration and/or the susceptibility to external fields should be sufficient to establish longrange order. Looking at Nature, neither high concentrations, nor high susceptibilities are required. Here, we present a route toward macroscopically highly ordered materials at extremely high dilution (less than 0.3% in water). Following Onsager's hard rod model, [19] long range order at this concentration requires stiff rods of several micrometers long. Instead, we find that the order develops (slowly) through the interaction between a self-assembling chromophore and a semiflexible polymer; neither of the two components form structures in the micrometer range. In earlier work with DNA [20,21] or the chromonic liquid crystal DSCG [22,23] as the self-assembling material, the addition of polymers typically Control over the organization of assemblies from molecular dimensions up to the macroscopic length scale is an outstanding challenge in science, above all for materials in high dilution. Instead of inducing order by generating very long and stiff structures, an alternative approach is studied: a two-component assembly of a semiflexible polymer with a (self-assembling) chromonic liquid crystal. By following the structure formation in time using different techniques, a mechanistic model is proposed that explains how such unusually well-defined materials can be created from flexible components. It is concluded that at this very low concentration (>99.6% water), these macro scopically organized structures can only be formed when the energies between different assembly states and their interconversion rates are properly balanced. This may, however, be in reach for a wide range of materials, which makes this a generic route toward high definition at low concentration without the need for long and rigid building blocks. Figure 7. Schematic representation of the hierarchical assembly process to obtain macroscopic long-range order at high dilution without the use of highly rigid components. full paper 9016 wileyonlinelibrary.com
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.