Chromatic and dynamic characteristics of some photochromes in the components of bifunctional photochromic and electro-optical devices

This work is part of a research project whose final aim is to realise prototypes of bifunctional photochromic and electro-optical devices. The photochrome will be incorporated in films composed by nematic liquid crystals dispersed in a polymeric matrix or in fluid monomer emulsions. To choose suitable photochromic components, the behaviour of some compounds (four naphtho-spiro-indolino-oxazines and a nitromethoxy-spiropyran) was investigated in the components of the matrix (liquid crystals and monomers) and compared with that in organic solvents. The colour-forming and colour-bleaching kinetics were determined. The molecules investigated, while maintaining their photochromic behaviour, generally exhibited a better colorability in liquid crystals and monomers, due to decreasing of the bleaching rate. The results of this work indicate that two of the molecules investigated have the prerequisites of colorability, reversibility and durability to be used in the bifunctional devices. Preliminary tests on the behaviour of a prototype of bifunctional film are reported.