Broadband Light Management with Thermochromic Hydrogel Microparticles for Smart Windows

Li, Xin‐Hao; Liu, Chang; Feng, Shien‐Ping; Fang, Nicholas X.

doi:10.1016/j.joule.2018.10.019

Cited by 306 publications

(285 citation statements)

References 46 publications

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“…The obtained thermoresponsive PNIPAm and P(NIPAm-co-BA) gels were coated on a glass plate with a thickness of 5 mm. Then, a glass plate coated with P(NIPAm-co-BA) was placed on a logo-engraved paper, and the light transmission and blocking were examined by irradiating artificial sunlight at each temperature (25,33, and 45°C) on a glass plate. The results of this experiment are shown in Figure 5.…”

Section: Application Of P(nipam-co-ba) Hydrogel For Smartmentioning

confidence: 99%

See 1 more Smart Citation

Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

Park

Jang

Sim

et al. 2019

International Journal of Polymer Science

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Thermoresponsive polymers that exhibit phase transition in response to temperature change can be used as material for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermoresponsive polymers for a smart window that can be used over a wide temperature range is required. Therefore, to obtain smart window materials that can be used at various temperatures, three-dimensional thermoresponsive P(NIPAm-co-BA) hydrogels were prepared by free radical polymerization from main monomer N-isopropylacrylamide, comonomer butyl acrylate, and crosslinking agent N,N′-methylenebisacrylamide (MBAm) in this study. This study examined the effect of BA content on the lower critical solution temperature (LCST) and the solar light transmittance of crosslinked P(NIPAm-co-BA) hydrogel films. The LCST of hydrogel films was found to be significantly decreased from 34.3 to 29.5°C with increasing BA content from 0 to 20 mol%. It was found that the transparent films at T=25°C (T<LCST) were converted to translucent films at a higher temperature (T=45°C) (T>LCST). These results suggested that the crosslinked P(NIPAm-co-BA) hydrogel materials prepared in this study could have high potential for application in smart window materials.

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Section: Application Of P(nipam-co-ba) Hydrogel For Smartmentioning

confidence: 99%

“…In the case of copolymers using comonomers, there have been reports of controlling LCST as a control of the hydrophilic and hydrophobic groups of monomers [23][24][25]. However, in these reports, the difference in light transmittance (ΔT) between light transmission and light interruption is relatively low, about 60%.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

Park

Jang

Sim

et al. 2019

International Journal of Polymer Science

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“…As the energy consumption of buildings accounts for a great proportion of the social total energy consumption, it is imperative to open up new passive energy-saving technologies to improve the energy efficiency of buildings [ 1 , 2 , 3 ]. As an important part of building enclosures, the design of window systems is the most serious challenge for the energy saving of buildings and is also closely related to the degree of indoor comfort [ 2 , 3 ]. Windows with large areas in modern public buildings are required to provide good natural lighting but also to greatly increase solar heat gain.…”

Section: Introductionmentioning

confidence: 99%

Design of Transparent Metasurfaces Based on Asymmetric Nanostructures for Directional and Selective Absorption

Yang

Liu

2020

Materials

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Maximizing the solar heat gain through windows in winter and minimizing the solar radiation entering the room in summer are of great significance for the energy saving of buildings. Here, we present a new idea for transparent metasurfaces, based on asymmetric metal/insulator/metal (MIM) nanostructures, which can be switched back and forth between absorbing and reflecting solar radiation by reversing the sample orientation. Owing to the fundamental mode of a low-quality-factor resonance, a selective near-infrared absorption is obtained with an absorption peak value of 90% upon front illumination. The average solar absorption (45%) is about 10% higher than that (35%) of reported transparent absorbers. The near-infrared light is also strongly and selectively reflected upon back illumination and a reflection peak value above 70% is observed. Meanwhile, the average visible transmission of the metasurface is above 60%, which is about 1.6 times that (36%) of previous transparent metasurface absorbers. In addition, Cu material can replace the noble metals in this work, which will greatly reduce the manufacturing cost. Owing to the attractive properties of directional and selective absorption, passive operation mode, and low cost of the materials, the metasurfaces have promising prospects in building energy saving or other solar applications where surface transparency is desirable.

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“…Such programmed optical devices have potential for use in energy saving smart window applications for example. [32][33][34][35][36][37][38][39][40][41][42] propoxy)benzoate)), which we used for the fabrication of the CLC polarizers. [27] The photoinitiator Irgacure 651 (2,2-dimethoxy-1,2diphenylethan-1-one) and UV-absorber Tinuvin 328 (2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol) were purchased from Ciba Specialty Chemical Inc.…”

Section: Resultsmentioning

confidence: 99%

Temperature‐Responsive Polymer Wave Plates as Tunable Polarization Converters

Kragt

Gessel

Schenning

et al. 2019

Advanced Optical Materials

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components of electro-magnetic waves. The simplest wave plates have a homogeneous uniaxial birefringence (Δn) with a thickness (d) and induce a phase shift between the two orthogonal waves according toin which λ is the wavelength and k the induced phase shift divided by 2π. [1,8,9] Liquid crystals (LCs) are frequently used as wave plate materials. By programming the Δn and d of a uniaxial aligned LC quarter-and half-wave plates can be easily fabricated. Also achromatic polarization converters can be obtained by stacking multiple wave plates using the principle of retardation compensation or using configurations involving twisted nematic LCs. [1,[8][9][10][11][12][13][14][15][16][17][18] Wave plates based on nonpolymerized LCs in cells can also be switched using electric fields, which among others resulted in the billion dollar LC display industry. [1,19,20] To widen its application range it would be appealing to make wave plate films that are responsive to other stimuli such as temperature. However, stimuli-responsive polymer wave plates have never been reported so far.We recently reported on a reflective LC coating based on a semi-interpenetrating polymer network (semi-IPN) composed of a LC elastomer (LCE) and a helical LC network (LCN). The coating showed a fast and reversible decrease in reflection band intensity with increasing temperature, which could be tuned by the polymer network density. [21] In this work, we developed temperature-responsive polymer wave plates, which reversibly change from a full-wave to a half-wave plate upon heating. The wave plate consists of a uniaxial aligned nematic semi-IPN in which a non-crosslinked LCE interpenetrates through an LCN. Upon heating above the nematic-to-isotropic transition temperature (T N-I ) of the semi-IPN, the LCE loses order and the effective Δn of the material halves, while d remains constant, thereby changing the polymer film from a full-wave to a half-wave plate. We demonstrate its function by sandwiching the temperatureresponsive wave plate between two identical cholesteric LC (CLC) polarizers reflecting right-handed circular polarized (CP) light around the λ for which the wave plate is operative (Figure 1). Below the T N-I , the left-handed CP light transmitted by the first polarizer is effectively not affected by the full-wave plate and thus also transmitted by the second polarizer, resulting in an overall reflectivity of 50%. Upon heating above T N-I , the wave plate turns into a half-wave plate, which converts the A temperature-responsive polarization converter, which reversibly changes from a full-wave to a half-wave plate upon heating, is developed. The polymer wave plate has a controlled thickness and is based on a uniaxial aligned nematic semi-interpenetrating network coating containing a specific concentration of a non-crosslinked liquid crystal elastomer. Upon heating, the effective birefringence of the wave plate halves without changing the thickness. The function of the wave plate is demonstrated by sandwiching the tunable polarization conver...

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Broadband Light Management with Thermochromic Hydrogel Microparticles for Smart Windows

Cited by 306 publications

References 46 publications

Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

Design of Transparent Metasurfaces Based on Asymmetric Nanostructures for Directional and Selective Absorption

Temperature‐Responsive Polymer Wave Plates as Tunable Polarization Converters

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