3.5 Inorganic Organic Hybrid Materials

Besides the three classes of thermochromic additives discussed previously, hybrid organic-inorganic thermochromic systems are under development in order to combine the advantages of both material classes with one another. A hybrid organic-inorganic thermochromic film is described in [35]. The multilayer film based on polyoxomethalate clusters K _12.5Na _1.5[NaP ₅W ₃₀O ₁₁₀] was prepared by a layer-by-layer self-assembly method. The colour changes gradually from yellowish to blue when it is subjected to temperatures between 120 and 180 C. Such hybrid materials could be favoured for thermochromic switching temperatures above 100 C provided that a high transparency in the on and off states is not required.

Hybrid composites of polydimethylsiloxane and gold nanoparticles with an adsorbed monolayer of 1-alcanethiols (1-decanethiol or 1-dodecanethiol) afforded a versatile irreversible colour change [36]. The effect is triggered above 220 C as a result of desorption of the alcanethiol molecules from the gold surfaces which leads to the irreversible formation of particle aggregates.

Another example of a hybrid organic-inorganic system is described in [37]. Thermochromic properties are obtained by doping a film of polyaniline, poly( o-toluidine) and poly( o- methoxyaniline) or their polyvinyl alcohol-containing composites with sulfate. Conformational changes are the reason for the temperature-triggered colour change obtained. Poly(di- n-hexylsilane)-containing zirconia hybrid thin films show thermochromic properties by transformation of the Si Si main chain. The preparation was carried out by a sol-gel reaction of di- n-hexylsilane acetoacetoxyethyl methacrylate block copolymers and zirconium alkoxide [38]. A...