Dendrimeric triphenylbenzenes: helical versus zig-zag arrangement in columnar mesophases

ABSTRACTA small series of dendrimers consisting of a star-shaped triphenylbenzene core unit and bulky lateral groups was synthesised and their mesomorphic properties were investigated via differential scanning calorimetry, polarising optical microscopy and small- and wide-angle X-ray scattering (WAXS). The dendrimers showed two enantiotropic hexagonal columnar mesophases. The combination of temperature-dependent and fibre-extruded WAXS revealed a helical arrangement in the low-temperature and a zig-zag orientation in the high-temperature mesophase. Furthermore, at the mesophase-to-mesophase transition, the intracolumnar reorganisation and the intercolumnar lattice extension occurred at different time scales, with the latter process being the slower one.