In the last decade chromogenic polymers have found lively interest, especially regarding sun protecting glazing systems. The background for sun protection is based on absorption and reflection phenomena of solar ray.

According to the external stimulus which affects their optical properties chromogenic materials are separated into subclasses, e.g. thermochromic, electrochromic and photochromic polymers. Presented work focuses on thermochromic
• hydrogels by endowing indicator dyes
• polyolefines by embedding leuco dye systems

The origin of thermochromism in hydrogels endowed with indicator dyes is a temperature dependent molecular interaction between dye and gel matrix which affects the dye structure. Neither the dyes nor the hydrogels exhibit thermochromic properties themselves. In the present study highly transparent hydrogel networks – based on crosslinked polymer / indicator dye systems – are obtained. Novel microenvironment properties are resulting. The outstanding property of this material class is the possibility to switch from colourless to colour on heating – suitable for absorption effects.

Thermochromic thermoplastics can be obtained by doping the polymer matrix with a thermochromic complex. Thermochromic polyolefin foils based on leuco dye-developer-solvent systems which withstand the flat foil extrusion process will be presented. Colour and switching temperature of the thermochromic foils can be tailored. A linear dependence of the colour intensity on the additive concentration was found. Furthermore, the surface tension of thermochromic foils, as an indicator for potential migration processes, will be discussed.