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Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings.

Khandelwal H, Loonen RC, Hensen JL, Debije MG, Schenning AP - Sci Rep (2015)

Bottom Line: Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector.We have also fabricated a switchable IR reflector which can also generate electricity.These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

View Article: PubMed Central - PubMed

Affiliation: 1] Functional Organic Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven, University of Technology, Den Dolech 2, 5600 MB Eindhoven, the Netherlands [2] Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands.

ABSTRACT
Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

No MeSH data available.


Related in: MedlinePlus

Transmission spectra of cholesteric liquid crystal gela) before polymerization b) after photo-polymerization with the influence of the ITO coated glass plates omitted and c) after photo-polymerization including the absorbance of ITO and d) Photograph of the IR reflector demonstrate the transparency in the visible region.
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f3: Transmission spectra of cholesteric liquid crystal gela) before polymerization b) after photo-polymerization with the influence of the ITO coated glass plates omitted and c) after photo-polymerization including the absorbance of ITO and d) Photograph of the IR reflector demonstrate the transparency in the visible region.

Mentions: To induce a cholesteric phase, chiral dopants CD-267 and CB-15 were added to the host nematic liquid crystal mixture. To fabricate the broadband IR reflector, a concentration of chiral dopant was chosen such that the reflection peak of the Ch-LC mixture was centered around 1000 nm. Figure 3a shows the transmission spectrum of the Ch-LC gel before polymerization. The reflection peak of the mixture was found to be centered around 970 nm with a typical bandwidth of 105 nm. To achieve the broadband IR reflection, a pitch gradient was attained using photoinduced diffusion during photopolymerization1947. A UV-intensity gradient was generated by adding 2.0 wt % of the UV-absorber Tinuvin- 328 to the mixture. Upon UV irradiation, the intensity gradient induces the chiral monoacrylate (monofunctional) molecule to undergo faster polymerization at the top compared to the bottom of the sample. This depletion of monoacrylate at the top causes diffusion of monoacrylate molecules from the bottom towards the top of the film. Thus, diffusion of monoacrylate leads to non-uniform distribution of chiral dopant (monoacrylate) in the liquid crystal gel and thus a pitch gradient is generated3548. Figure 3b shows the transmission spectrum corrected for the electrode layers (ITO), to emphasize changes in the active reflecting material of the liquid crystal gel after polymerization. The Ch-LC polymer gel reflects a broader band of infrared light from 700 to 1400 nm while remaining predominantly transparent in the visible region (88.5% transmission at 550 nm, Figs. 3b,d). The ITO layer on the glass plate absorbs in the infrared region (Supplementary Fig. S1) as can be seen in the non-normalized (with respect to the ITO plate) transmission spectrum (Fig. 3c). However, absorption of ITO does not have a significant impact on energy savings in a building because it only absorbs light primarily >1300 nm.


Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings.

Khandelwal H, Loonen RC, Hensen JL, Debije MG, Schenning AP - Sci Rep (2015)

Transmission spectra of cholesteric liquid crystal gela) before polymerization b) after photo-polymerization with the influence of the ITO coated glass plates omitted and c) after photo-polymerization including the absorbance of ITO and d) Photograph of the IR reflector demonstrate the transparency in the visible region.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487232&req=5

f3: Transmission spectra of cholesteric liquid crystal gela) before polymerization b) after photo-polymerization with the influence of the ITO coated glass plates omitted and c) after photo-polymerization including the absorbance of ITO and d) Photograph of the IR reflector demonstrate the transparency in the visible region.
Mentions: To induce a cholesteric phase, chiral dopants CD-267 and CB-15 were added to the host nematic liquid crystal mixture. To fabricate the broadband IR reflector, a concentration of chiral dopant was chosen such that the reflection peak of the Ch-LC mixture was centered around 1000 nm. Figure 3a shows the transmission spectrum of the Ch-LC gel before polymerization. The reflection peak of the mixture was found to be centered around 970 nm with a typical bandwidth of 105 nm. To achieve the broadband IR reflection, a pitch gradient was attained using photoinduced diffusion during photopolymerization1947. A UV-intensity gradient was generated by adding 2.0 wt % of the UV-absorber Tinuvin- 328 to the mixture. Upon UV irradiation, the intensity gradient induces the chiral monoacrylate (monofunctional) molecule to undergo faster polymerization at the top compared to the bottom of the sample. This depletion of monoacrylate at the top causes diffusion of monoacrylate molecules from the bottom towards the top of the film. Thus, diffusion of monoacrylate leads to non-uniform distribution of chiral dopant (monoacrylate) in the liquid crystal gel and thus a pitch gradient is generated3548. Figure 3b shows the transmission spectrum corrected for the electrode layers (ITO), to emphasize changes in the active reflecting material of the liquid crystal gel after polymerization. The Ch-LC polymer gel reflects a broader band of infrared light from 700 to 1400 nm while remaining predominantly transparent in the visible region (88.5% transmission at 550 nm, Figs. 3b,d). The ITO layer on the glass plate absorbs in the infrared region (Supplementary Fig. S1) as can be seen in the non-normalized (with respect to the ITO plate) transmission spectrum (Fig. 3c). However, absorption of ITO does not have a significant impact on energy savings in a building because it only absorbs light primarily >1300 nm.

Bottom Line: Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector.We have also fabricated a switchable IR reflector which can also generate electricity.These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

View Article: PubMed Central - PubMed

Affiliation: 1] Functional Organic Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven, University of Technology, Den Dolech 2, 5600 MB Eindhoven, the Netherlands [2] Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands.

ABSTRACT
Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

No MeSH data available.


Related in: MedlinePlus