Synthesis and characterization of polymerizable photochromic liquid crystals containing a spiro-oxazine group

Novel polymerizable photochromic liquid crystal materials containing either the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]naphth[2,1-b][1,4] oxazine] group or the 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H] pyrido[3,2-f][1,4]benzoxazine] group as the photochromic moiety, and the bi phenylene unit as the mesogenic moiety, were synthesized. Thermal and physi cal properties of the compounds were examined using differential scanning c alorimetry, optical polarizing microscopy, wide-angle X-ray diffractometry and UV-visible spectrophotometry. The photochromic compounds containing bot h photochromic and mesogenic moieties showed metastable mesophases; These t ended to crystallize with time and on heating. The crystallization behaviou rs were strongly dependent on the structure of the terminal group of alkyle ne spacer and the position of the spiro-oxazine bound to the mesogen.