Liquid Crystalline Phase Transition in Hexakis(4-(N-(41-alkoxyphenyl)iminomethyl)phenoxy)cyclotriphosphazene

Abstract A new series of cyclotriphosphazenes bearing Schiff bases with different carbon number alkoxy end groups(HAICP) in the side chains were synthesized and their phase transitions and liquid crystallinity were studied using DSC measurements and polarizing microscope observations. We found a monotropic Sml phase for n = 3 and an enantiotropic Sml phase for n = 4 −5, enantiotropic Sml, SmC and SmA phases for n = 6 – 7, enantiotropic SmC and SmA phases for n = 8 – 10, and enantiotropic Sm2, SmC and SmA phases for n=11 and 12 in the HAICP series. The Sml phase is a low-order uniaxial smectic phase and Sm2 phase is a low-order biaxial smectic phase. The melting point decreased with an increase in the end alkoxy carbon number, n, of the cyclotriphosphazenes, but the clearing point decreased with an increase in n. As a result, the mesomophic region expands with an increase in n. The melting and clearing points do not show clear odd-even effects, which is caused by the peculiar shape of the cyclotriphosphazenes.