Easily Processable Temperature-Responsive Infrared-Reflective Polymer Coatings

Abstract

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.

Environmentally responsive photonic polymers

“…That is why a mixture of an SCLCP with a low molecular weight chiral dopant having this transition resulted in a polymer film that shifted reversibly from 1250 to 2350 nm upon cooling from 57 to 17 1C. 54 Another material having a smectic to cholesteric transition was obtained by coating short oligomers of reactive LCs. This yielded coatings that could shift between 1195 and 701 nm or between 754 to 484 nm, covering thereby the entire visible range.…”

Polymer Stabilized Cholesteric Liquid Crystal Siloxane for Temperature-Responsive Photonic Coatings

“…Monomers M1, M2 and M3 were synthesized and fully characterized by 1 H NMR and 13 C NMR (Figures S1-S5). Although the complete synthesis of M1 has been reported [25,34], here, we use a new approach to synthesize the intermediate product, 4-(hex-5-en-1-yloxy)benzoic acid (1) with a higher yield, by using ethyl 4-hydroxybenzoate as the reactant followed by dehydration of the ester group. The chiral dopant M2 is a new molecule designed to achieve a prominent helical twisting effect at low concentration.…”

“…In our previous work, we prepared a temperature-responsive coating by blade-coating a mixture of oligomeric polysiloxane and a chiral dopant [25]. This non-crosslinked Ch-LC coating possessed a Sm-Ch phase transition, leading to a~1200 nm bandshift within the IR region upon changing the temperature between room temperature and 66 • C. In this work, we developed a photopolymerizable, Ch-LC polysiloxane mixture for the preparation of a temperature-responsive polymer network-stabilized photonic coating.…”

Humidity-gated, temperature-responsive photonic infrared reflective broadband coatings

“…27,28 A coating of a non-crosslinked, oligomeric Ch-LC mixture was recently developed showing a shi of the narrow IR-reection band to shorter wavelengths upon increasing the temperature. 29 However, due to non-crosslinked nature of the coating, reaching temperatures lower than 16 C, resulted in the reectivity being irreversibly lost. Cross-linked thermochromic photonic systems based on hydrogels 30,31 have been reported: upon heating or cooling of the surrounding water, reection bands are able to shi in the visible light range.…”