LIQUID-CRYSTALLINE PHASE-TRANSITIONS IN HEXAKIS(4-(4'-HEPTYLOXY)BIPHENOXY)CYCLOTRIPHOSPHAZENE

Hexakis(4-(4'-heptyloxy)biphenoxy)cyclotriphosphazene (HHCP) was synthesized from hexachlorocyclotriphosphazene and 4-heptyloxy-4'-hydroxybiphenyl. The mesogenicity of HHCP was studied by DSC, FTIR spectroscopy and polarizing microscopy. Enantiotropic smectic C and nematic phases were observed between 450 and 455 K and 455 and 456 K, respectively, on heating, and between 456 and 455 K (nematic) and 455 and 440 K (smectic C) on cooling from the isotropic liquid phase. The introduction of the heptyloxybiphenoxy groups as side chains into cyclotriphosphazene has generated the liquid crystalline phase. FTIR spectroscopy showed that the P=N and P-O-(C) stretching vibrations converted to lower frequencies from 1224 to 1210 cm(-1) and from 920 to 910 cm(-1), respectively, at the crystalline (C)S-C phase transition. This result suggests that the state of the cyclotriphosphazene ring dramatically changes near the C-S-C phase transition.