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In order to obtain a material with high solar modulation ability $(\mathrm{\Delta }{T}_{\mathrm{\text{sol}}})$ and crystalline quality, ${\mathrm{\text{VO}}}_2$ films were prepared on quartz glass substrates using RF magnetron sputtering under various oxygen partial pressures. Their phase, surface, transmittance, and film sheet resistance properties were analyzed. As the oxygen partial pressure increased, the luminous transmittance $(T_{\mathrm{\text{lum}}})$ of the film increased to as high as 55.6%, while the $\mathrm{\Delta }{T}_{\mathrm{\text{sol}}}$ first increased to a maximum of 10.8% and then decreased. This paper is a meaningful aid in the application of ${\mathrm{\text{VO}}}_2$ films to smart windows.

A series of thermochromic polypropylene foils were prepared by embedding various leuco dye-developer-solvent systems in the polymer matrix. Bisphenol A, laurylgallate, ethylgallate and p-hydroxybenzoic acid methyl ester were used as developers, crystal violet lactone and 3,3-bis-(1-n-butyl-2-methyl-3-indolyl)-phthalide as dyes and 1-octanoic acid methyl ester as solvent. The molar ratio between the three components of the investigated leuco dye-developer-solvent systems was kept constant. All obtained polypropylene foils exhibit an excellent thermochromic behavior. The foils, prepared by extrusion technology, switch from color to colorless with increasing temperature. The influence of molecular structure of the developer on the intensity of the colored state and the influence of a developer-surfactant complex on the resulting thermochromic properties were investigated. The results are presented and discussed in detail according to a molecular model suggesting that the ring-opening process of the leuco dye is triggered by the formation of dye-developer complexes via H-bondings.

Thermochromic polymers will play an extremely important role in the next future. The physical background of thermochromism and the state of development of thermochromic polymers based on light absorption effects are reported. In detail, the interactions between the polymer matrix and the thermochromic composite — composed of leuco or indicator dyes — are discussed on a molecular level. Thermochromic hydrogels with extremely high transparency, an outstanding switching behavior from colorless to colored or between different colors is presented. Preparation of thermosetting and thermoplastic polymers, including the resulting optical, and, for the first time, the mechanical properties are discussed in relation to matrix tuned high-resistant microcapsules.