Switchable smart windows using a biopolymer network of cellulose nanocrystals imposed on a nematic liquid crystal

Abstract

A polymer stabilized liquid crystal (PSLC) system formed by a nematic contained in a biopolymer network of cellulose nanocrystals, exhibiting many attractive features, is demonstrated. The threshold or the minimum voltage needed to operate the electro-optic device does not depend on the concentration of the polymer, a feature that is in contrast to the standard PSLC systems. A second point, more important from the driving circuit point of view, is that the voltage-off response time drastically reduces and even becomes practically invariant over the thermal range of the nematic phase. A smart window fabricated using this biopolymer network system exhibits good contrast between the scattering and transparent states driven by voltage and shows an exceptionally high haze factor. A highlight of the device fabrication is that the employed protocol is facile, making it appealing for a potentially viable smart window application.

Pseudopeptidic Polymer Microsphere-Filled Liquid Crystals as High-Performance Light-Scattering Switches

“…F1 was then subjected to ROMP under an inert atmosphere of argon using the Grubbs second-generation catalyst G2 (SIMes)(PCy 3 )(Cl) 2 Ru = CHPh (where SIMes: 1,3-dimesityl-4,5-dihydroimidazol-2ylidene and Cy: cyclohexyl) to give the corresponding polymer PF (Scheme 1). 35,36 The conversion of monomer to polymer was confirmed by 1 H NMR spectral analyses. The olefinic protons (−CHCH−) appearing as a singlet at δ = 6.20 ppm (Figure 1) in the 1 H NMR spectrum of F1 disappeared upon polymerization along with the simultaneous appearance of a new group of peaks at around δ = 5.1−5.8 ppm (Figure 1).…”

“…Yield: 86%; appearance: yellowish syrup. 1 H NMR (300 MHz, CDCl 3 ): δ 0.93 (d, J = 9.9 Hz, 1H), 1.24 (d, J = 9.0 Hz, 1H), 2.52 (m, 2H), 3.14 (s, 2H), 3.47 (m, 2H), 3.77 (s, 3H), 5.03 (m, 1H), 6.20 (s, 2H), 7.04−7.32 (m, 5H); 13 added the Grubbs second-generation catalyst (0.0012 g, 0.0014 mmol) and left stirring for 12 h at room temperature under an argon atmosphere. After completion of the reaction as monitored by TLC, the resultant mixture was quenched by adding 3 mL of ethyl vinyl ether.…”

“…The demand for dynamic smart windows for energy-harvesting devices − led to the development of technologies based on photochromic particle-, electrochromic particle-, suspended particle-, and liquid crystal (LC)-based systems. Among all, LC-based devices are more economical and efficient owing to their reliability, cost effectiveness, and low operating voltage requirement .…”

Self-assembled liquid crystal architectures for soft matter photonics

“…The composite could achieve high reflectivity in the near-infrared range while maintaining high transmittance in the visible spectral regime, making it suitable for smart window applications. Besides, smart windows were also designed based on a biopolymer-stabilized LC system composed of a CNC-based network and a nematic LC 288 . This system shows rapid voltage-off response time, good voltage-driven contrast between the scattering and transparent states, and a high haze factor.…”

Multi‐stimuli‐responsive and Multi‐functional Smart Windows

“…Liquid crystals can also be used in electrochromic smart windows. [33,[50][51][52][53] In the absence of an electric field, the disordered liquid crystals scatter the incident light, making the window translucent or opaque. Under the application of an electric field, the liquid crystals can be aligned to make the window transparent.…”