Thermotropic Materials for Adaptive Solar Control


Article Preview

Thermotropic materials offer an immense potential in adaptive solar control. They combine specific optical properties like absorbance and reflection, and high stability against solar radiation and heat with technology compatible processing capacities. Therefore, they represent perfect energy efficient materials. In detail, polymer blends, polymer-based hydrogels, casting resins, and thermoplastic films with a reversible temperature-dependent switching behavior have been investigated. Here a comparative evaluation of the different concepts with a view to their application in adaptive solar control is presented. Own current results exploit the well-known phase change materials and describe its use for adaptive solar control with extruded films or highly stable casting resins with thermotropic properties. Therewith, the status has changed from diffuse sunblind systems to intrinsic solar energy reflecting materials and a first smart window system based on phase change materials has now commercialized [1]. In summary: It is amazing that the solar energy itself is used as a promoter against solar heat.



Edited by:

Pietro Vincenzini, Yoon-Bong Hahn, Salvatore Iannotta, Andreas Lendlein, Vincenzo Palermo, Shashi Paul, Concita Sibilia, S. Ravi P. Silva and Gopalan Srinivasan




R. Ruhmann et al., "Thermotropic Materials for Adaptive Solar Control", Advances in Science and Technology, Vol. 77, pp. 124-131, 2013

Online since:

September 2012




[1] A. Seeboth, R. Ruhmann, O. Muehling, Thermotropic and Thermochromic Polymer Based Materials for Adaptive Solar Control, Materials 3 (2010) 5143-5168.


[2] S. Selkowitz, E.S. Lee, Advanced Fenestration Systems for Improved Daylight Performance, Daylighting (1998).

[3] S. Selkowitz, O. Aschehoug, E. S. Lee, Advanced Interactive Facades – Critical Elements for Future Green Buildings? GreenBuild (2003).

[4] T. Karlessi, M. Santamouris, K. Apostolakis, A. Synnefa, I. Livada, Development and testing of thermochromic coatings for buildings and urban structures, Solar Energy 83 (2009) 538-551.


[5] M. Saeli, C. Piccirillo, I. P. Parkin, R. Binions, I. Ridley, Energy modelling studies of thermochromic glazing, Energy and Buildings 42 (2010), 1666-1673.


[6] A. Jonsson, A. Roos, Evaluation of control strategies for different smart window combinations using computer simulations, Solar Energy 84 (2010), 1-9.


[7] P. Nitz, J. Ferber, R. Stangl, H. R. Wilson, V. Wittwer, Simulation of multiply scattering media, Solar Energy Mater. Sol. Cells 54 (1998) 297-307.


[8] K. Resch, G. M. Wallner, R. Hausner, Phase separated thermotropic layers based on UV cured acrylate resins—Effect of material formulation on overheating protection properties and application in a solar collector, Solar Energ. 83 (2009) 1689-1697.


[9] O. Muehling, A. Seeboth, T. Haeusler, R. Ruhmann, E. Potechius, R. Vetter, Variable solar control using thermotropic core/shell particles, Sol. Energ. Mater. Sol. Cell. 93 (2009) 1510-1517.


[10] Y. Hirokawa, T. Tanaka, Volume phase transition in a nonionic gel, J. Chem. Phys. 81 (1984), 6379-6380.

[11] M. Zrínyi, A. Szilágyi, G. Filipcsei, J. Fehér, J. Szalma, G. Móczár, Smart gel-glass based on the responsive properties of polymer gels, Polym. Adv. Technol. 12 (2001) 501-505.


[12] D. Chahroudi, U.S. Patent 4, 307, 942 (1981).

[13] A. Beck, W. Koerner, H. Scheller, J. Fricke, W. Platzer, V. Wittwer, Control of solar insolation via thermochromic light-switching gels, Sol. Energ. Mater. Sol. Cell. 36 (1995) 339-347.


[14] A. Seeboth, D. Lötzsch, E. Potechius, Phase transitions and phase separations in aqueous polyether systems, Colloid Polym. Sci. 279 (2001) 696-704.


[15] A. Seeboth, J. Kriwanek, D. Lötzsch, A. Patzak, Chromogenic polymer gels for reversible transparency and color control with temperature at a constant volume, Polym. Adv. Technol. 13 (2002) 507-512.


[16] H. Watanabe, Intelligent window using a hydrogel layer for energy efficiency. Sol. Energ. Mater. Sol. Cell. 54 (1998) 203-211.

[17] T. Bicer, C. Schwitalla and H. Gödecke, D.E. Patent 19, 825, 984 (2000).

[18] K. Resch, G. M. Wallner, R. W. Lang, Spectroscopic investigations of phase separated thermotropic layers based on UV cured acrylate resins, Macromol. Symp. 265 (2008) 49-60.