A 1,3,5-benzenetrisamide with three pending hexaalkoxytriphenylene groups has been synthesized as an example of an interesting class of intermolecular H-bond-stabilized columnar discotic liquid crystalline materials. The material forms a plastic hexagonal discotic phase that does not crystallize on cooling from the isotropic phase, even after annealing for a few days at room temperature. X-ray and computational studies provide a detailed model for the organization of this material. The charge carrier mobility, 0.12 cm2 V-1 s-1 at 180 °C, is the highest ever reported for liquid crystalline triphenylene systems, and even increases with temperature. The factors responsible for this behavior are discussed.

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The dynamics and phase behavior of the discotic liquid crystalline compound hexahexyloxytriphenylene (HAT6) and a derivative were studied by broad-band dielectric spectroscopy, differential scanning calorimetry, X-ray diffraction and optical microscopy. While the pristine compound HAT6 forms both a columnar mesophase (Col h ) and a plastic crystal phase, no liquid crystallinity was observed for the highly asymmetric compound HAT6-C 10 Br. This paper focuses on the dielectric relaxations in the plastic crystal phase. For HAT6-C 10 Br, a Ôhigh temperatureÕ glass transition, manifested by a Vogel-Fulcher-Tammann (VFT) type a 2 -process, was found at À31°C that was assigned to the columnar glass transition in accordance with previous literature. The main result of our study is the observation of a second, low-temperature VFT process (a 1 ) for both compounds, which indicates co-operative liquid dynamics within the framework of the plastic crystal order at temperatures as low as À100°C. Comparison of these fast dynamics with relaxation data from polyethylene and polymer series with long alkyl groups identifies this process as a ÔhinderedÕ polyethylene-like dynamic glass transition that originates from the nanophase-separated, spatially confined fraction of aliphatic tails.

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The dynamics of the discotic liquid-crystalline system, hexakis ͑n-hexyloxy͒ triphenylene ͑HAT6͒, is considered in the frame of the phenomenological model for rate processes proposed by Berlin. It describes the evolution of the system in the presence of the long-time scale correlations in the system, and we compare this with experimental quasielastic neutron scattering of the molecular assembly of HAT6 in the columnar phase. We interpret the parameters of this model in terms of nonextensive thermodynamics in which rare events in the local fast dynamics of some parts of the system control the slower dynamics of the larger molecular entity and lead to a fractional diffusion equation. The importance of these rare local events to the overall dynamics of the system is linked to the entropic index, this being obtained from the data within the model approach. Analysis of the waiting-time dependence from momentum transfer reveals a Lévy distribution of jump lengths, which allows us to construct the van Hove correlation function for discotic liquid-crystalline system.