Phase identification of triphenylene-based discotic monomer and its main chain polymers

Abstract A monomer, 2,3,6,7,10,11-hexakispentyloxy triphenylene (HPT) possesses a triphenylene core as a discotic mesogen. Polymers containing this discotic mesogen have been studied using wide-angle X-ray and electron diffraction. HPT is known to show a discotic liquid crystal phase, noted as Dho (h for hexagonal bidimensional lattice, o for ordered molecular spacing in each column). In this paper, however, HPT liquid crystalline phases, heated up from the crystalline state and cooled down from the isotropic state, were characterized in the diameter dimensions. In addition. the diameters of the columns are close to a parameter of two separate crystals. A core orientation was, therefore, pr…

2H NMR studies of phase behaviour and molecular motions of doped discotic liquid-crystalline systems

Abstract A discotic triphenylene monomer as well as a dimer and a main chain polymer, all substituted with heptyloxy side groups, were doped with an electron acceptor (2,4,7-trinitrofluorenone (TNF)) to give charge transfer complexes. These doped systems were aligned in a magnetic field, thus proving their liquid crystallinity. 2H NMR measurements show that the electron acceptor molecules are incorporated into the columns built of triphenylene cores. In the charge transfer complex with the triphenylene monomer almost all the electron acceptor molecules stack in the columns even close to the clearing temperature T 1, while for the dimer and especially for the polymer a significant fraction o…

Molecular dynamics of discotic charge-transfer complexes, dielectric spectroscopy and2H NMR studie

Abstract Using a combination of solid state 2H NMR spectroscopy on selectively deuteriated samples and dielectric spectroscopy, the molecular dynamics of discotic charge-transfer (CT) complexes were investigated. These complexes show particular thermodynamic and flow properties. Considered were mixtures of low molar mass donors and acceptors, low molar mass donors with main chain acceptor polymers and covalently linked donor-acceptor twins with different lengths of the spacer. A main result is that correlated rotational motions of discotic molecules or groups about the columnar axis are observed in all systems except for the twin with the short spacer. This type of motion seems to be a gene…

Langmuir-Blodgett films from a polymer with triphenylene moieties in the side groups deposited on a quartz substratum with aluminium and gold electrodes show a dark conductivity in the plane of the Langmuir-Blodgett film. This dark conductivity is increased using gold electrodes as compared with aluminium electrodes. It depends in a superlinear way upon the applied electric field and is not enhanced by oxygen. The dark conductivity can be enhanced by doping the Langmuir-Blodgett films with iodine but it is not influenced by doping the Langmuir-Blodgett films with 2,4,7-trinitro-9-fluorenone. Upon excitation in the absorption band of the triphenylene moiety an in-plane photocurrent, which is…

In-Plane Anisotropy and Phase Change in Langmuir-Blodgett Films of a Triphenylene Derivative

Abstract The “in-plane anisotropy” of a triphenylene derivative in Langmuir-Blodgett (L.B.) films has been investigated. Upon heating, L.B. films exhibit a reversible phase transition appearing as an abrupt increase from a low to a high “in-plane anisotropy” corresponding to the formation of the same hexagonal liquid crystal phase observed in the bulk material at almost the same temperature, with the columnar axis aligned along the dipping direction.

Complex Ordering in Thin Films of Di- and Trifunctionalized Hexaalkoxytriphenylene Derivatives

We have used pressure−area isotherms, X-ray diffraction, atomic force microscopy, and infrared dichroism to study Langmuir and Langmuir−Blodgett films of 2,3,6,7,10,11-hexaalkoxytriphenylenes which...

Infrared absorption study of hexapentyloxytriphenylene A discotic liquid crystal

Abstract Fourier transform infrared absorption (FTIR) spectroscopy has been used to study a discotic liquid crystal. IR spectra are reported as a function of temperature for hexapentyloxytriphenyle...

Discotic liquid crystals at the air water interface

The monolayer properties of two types of discotic liquid crystals, hexasubstituted triphenylenes 1 and azo derivatives of phloroglucinol 5, were examined. First investigations show that these discotic liquid crystals form stable monolayers. It could be shown that electron acceptors insert into the monolayer of 1. Azo discs display a packing behaviour at the monolayer that is ascribed to a side-on packing of the molecules.

The synthesis of a new type of combined polymers containing both disc- and rod-like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod-like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X-ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid-crystalline phases.