Application of broadband infrared reflector based on cholesteric liquid crystal polymer bilayer film to windows and its impact on reducing the energy consumption in buildings

Khandelwal, Hitesh; Loonen, Rcgm Roel; Hensen, Jlm Jan; Schenning, Albertus P. H. J.; Debije, Michael G.

doi:10.1039/c4ta03047h

Cited by 81 publications

(48 citation statements)

References 43 publications

(52 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The mixtures are based on the mixtures previously used to make near-100% reflective Ch-LC films in cells. 14 However, a high brittleness was observed in the coatings using these Ch-LC mixtures, causing the LC to partially break during the cross-hatch tape test, resulting in an overall GT3 classification. Nevertheless, the second coating is well-adhered (GT0) to the first coating layer ( Figure S6 ).…”

Section: Resultsmentioning

confidence: 99%

Well-Adhering, Easily Producible Photonic Reflective Coatings for Plastic Substrates

Heeswijk

Kloos

Heer

et al. 2018

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

The development of well-adhering, easily producible photonic reflective coatings is still a challenge. Here, an easy-to-produce, industrial viable process is reported that uses a primer layer of the so-called type II photoinitiator to obtain an excellent adhesion between a plastic substrate and one-dimensional (1D) photonic liquid crystalline coatings. Furthermore, a good alignment of the reactive cholesteric liquid crystal mixture is obtained using a bar-coating process, without alignment layers or surfactants. After photopolymerization, cross-hatch tape tests show a good adhesion of the photonic coating having a reflection band of 50% transmission with almost no scattering. Additionally, we demonstrate the ability to create well-adhering ∼100% reflective coatings by coating double layers and the ability to create single-layered cholesteric broadband reflectors using solely a reactivity gradient created by the primer layer. Our new interfacial method gives new opportunities to use reflecting 1D photonic coatings in industrial processes and applications and allows the bonding of almost any polymer to a plastic substrate.

show abstract

Section: Resultsmentioning

confidence: 99%

Well-Adhering, Easily Producible Photonic Reflective Coatings for Plastic Substrates

Heeswijk

Kloos

Heer

et al. 2018

ACS Appl. Mater. Interfaces

Self Cite

View full text Add to dashboard Cite

show abstract

“…2d(iii) demonstrates that this coating is flexible and can be twisted without damaging its optical properties. The green color visible near the edges upon twisting is due to the angular dependence of the Bragg-like reflector: 16,32 the reflector returns to its initial orange color upon unbending the foil (Fig. 2d(iv)).…”

Section: Resultsmentioning

confidence: 99%

“…[16][17][18][19][20][21][22][23] Cholesteric LC systems are able to reflect light as a result of their self-organized molecular helices. Because of their liquid nature, these systems show a large temperature response but need to be sandwiched between two glass plates (in a cell architecture), 16,[24][25][26] which may not be practical or feasible in some instances, and in many cases, the temperature response of these polymers is limited and/or requires adsorbents. 27 Therefore, it remains a challenge to prepare temperature-responsive photonic coatings that are easily processable and show a large response.…”

Section: Introductionmentioning

confidence: 99%

Paintable temperature-responsive cholesteric liquid crystal reflectors encapsulated on a single flexible polymer substrate

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…The liquid‐crystallinity of the materials enabled the alignment of the nematic phase over large areas and the aligned films exhibit anisotropic absorption of linearly polarized light in the NIR region with a dichroic ratio of 4.3. The given absorption range is quite ideal with regard to smart window applications for heat management because the major part of the solar irradiation lies in this spectral regime . We assume that the SQ 1 nematic mesogen can also be embedded and oriented in common nematic LC hosts which are already utilized in commercial applications.…”

mentioning

confidence: 99%

Liquid‐Crystalline Squaraine Dyes with Anisotropic Absorption of Near Infrared Light

Soberats

Mayerhöffer

Würthner

2016

Advanced Optical Materials

View full text Add to dashboard Cite

CommuniCationconformational change of the squaraine backbone from a transoid to a cisoid planar π-scaffold (for DFT calculations for SQ 1, see Figure S1, Supporting Information) leading to several advantageous properties, namely, increase in stability, increase in fluorescence quantum yields and red-shift of the S 0 →S 1 (S 0 ; ground state, S 1 ; excited state) optical transition.[37] Squaraines with this molecular design have already found application as NIR emitters, [37] as conformation-sensitive exciton transfer systems, [38] in solar cells, [30,39,40] tumor imaging and photothermal therapy. [34,41] Interestingly, while none of the previously reported more than 20 dyes [37] showed LC properties, much to our surprise we discovered that SQ 1 bearing the most extended π-scaffold provided by two benzoquinolinium moieties ( Figure 1a) entered a mesophase above 153 °C.SQ 1 was prepared by a slight modification of our previously described synthetic methodology (Supporting Information) [37] and isolated as a dark crystalline powder. The liquid-crystallinity of SQ 1 was examined by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) measurements. POM image of SQ 1 sandwiched in between two glass plates show a Schlieren texture when cooled to 170 °C from the isotropic melt (Figure 2a). This texture indicates the formation of a nematic phase. POM and DSC measurements revealed that SQ 1 exhibits upon heating an exothermic transition corresponding to a crystal-crystal transition at 117 °C and an LC phase from 153 °C until isotropization at 182 °C (Figure 2b). On cooling process, the isotropic to nematic phase transition occurs at 182 °C and freezes into a glassy phase at 60 °C ( Figure 2b). It is noteworthy that the transitions between the isotropic state and the LC phase are of first order with low enthalpy values ( Figure 2b). This indicates a phase transition between low ordered phases (nematic-isotropic). The wide angle X-ray scattering pattern of SQ 1 at 170 °C shows two broad peaks at 23 and 4 Å, respectively ( Figure S2, Supporting Information). The first reflection in the small angle region most likely corresponds to the average distance between π-conjugated units. The broad nature of this peak suggests a low degree of order in the LC phase where the molecules organize with different distances between π-units ( Figure 1b). The second peak in the wide angle region corresponds to the diffuse halo generated by the alkyl chains. This XRD pattern is in accordance with a low ordered nematic phase. The absence of a sharp peak in the wide angle region corresponding to a particular π−π stacking distance (≈3-4 Å) discards a nematic discotic phase, despite the fact that the molecule exhibits a large π-conjugated core. The unusual shape of SQ 1 likely prevents the organization as a discotic nematic liquid crystal and promotes the formation of a calamitic-type nematic phase. Remarkably, the sample exhibits a similar XRD pattern after cooling the sample from 170 to 50 °C ( ...

show abstract

Application of broadband infrared reflector based on cholesteric liquid crystal polymer bilayer film to windows and its impact on reducing the energy consumption in buildings

Cited by 81 publications

References 43 publications

Well-Adhering, Easily Producible Photonic Reflective Coatings for Plastic Substrates

Well-Adhering, Easily Producible Photonic Reflective Coatings for Plastic Substrates

Paintable temperature-responsive cholesteric liquid crystal reflectors encapsulated on a single flexible polymer substrate

Liquid‐Crystalline Squaraine Dyes with Anisotropic Absorption of Near Infrared Light

Contact Info

Product

Resources

About