Synthesis and properties of new liquid crystalline compounds containing an indolinobenzospiropyranylazo group. Part 3

Two series of liquid crystalline dyes (series 1 and 2) containing novel mesogens incorporating a non-activated spiropyranylazo group have been synthesized. Those mesogens are derived from [1ʹ,3ʹ,3ʹ-trimethylspiro(2H-1-benzopyran-2,2ʹ-indoline)-6-yl] azobenzoic acid and 6-(phydroxyphenylazo)-1ʹ,3ʹ,3ʹ-trimethylspiro[2H-1-benzopyran-2,2ʹ-indoline] for the series 1 and 2, respectively. Their liquid crystalline properties were studied by differential scanning calorimetry, optical polarizing microscopy and electro-optical measurement. Most of the compounds in series 1 form the enantiotropic nematic phase, while compounds in series 2 form the monotropic nematic and SmA phase.