Phase transition in cyclic organophosphazenes: the effect of side chains on mesomorphism

Mesogenicity of five cyclotriphosphazenes and two cyclotetraphosphazenes wi th a similar dodecyl or dodecyloxy end and different central hard groups wa s studied. In the four cyclotriphosphazenes except for a cyclotriphosphazen e with phenyl derivative side chains, enantiotropic mesomorphic phases were observed. The order of the thermal stability in mesophase is phenylazobenz ene > phenyliminomethylphenyl > biphenyl groups for the side chains. The cy clotetraphosphazenes with biphenyl and Schiff base derivatives have lower m esomorphic thermal stability than cyclotriphosphazenes with the same side g roups.