SYNTHESIS AND CHARACTERIZATION OF A NEW THREE-ARMS-NINE-CHAINS DISCOTIC LIQUID CRYSTAL

A new three-arms-nine-chains discotic molecule has been synthesized,and the aggregation structure of the compound was measured by x-ray diffraction,infrared spectra,polarizing microscope,etc.From these evidences,the new discotic liquid crystal is found to have the discotic lammelar phase.

Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals

Disk-like liquid crystals（DLCs） can self-assemble to ordered columnar mesophases and are intriguing onedimensional organic semiconductors with high charge carrier mobility.To improve their applicable property of mesomorphic temperature ranges,we exploit the binary mixtures of electronic donor-acceptor DLC materials.The electron-rich2,3,6,7,10,11-hexakis（alkoxy）triphenylenes（C4,C6,C8,C10,C12） and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated.The mesomorphism of the1：1（molar ratio） mixtures has been characterized by polarizing optical microscopy（POM）,differential scanning calorimetry（DSC）,and small angel x-ray scattering（SAXS）.The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy（STM）.The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures.

PHASE STRUCTURES AND TRANSITION BEHAVIORS OF A TRIPHENYLENE DISCOTIC LIQUID CRYSTAL

The phase behaviors and structures of a triphenylene-derived discotic liquid crystal （LC） hexa-n-octoxyl- triphenylene （C8HET） were studied using the combined techniques of differential scanning calorimetry （DSC）, wide angle X-ray diffraction （WAXD）, selected area electron diffraction （SAED） and polarized light microscopy （PLM）. Onedimensional （1D） powder WAXD results at different temperatures coupled with DSC and PLM observations revealed that the C8HET compound possessed an LC phase and three different crystalline （K3, K2 and K1） phases below the isotropic （I） melt. The I←→ LC phase transition was thermodynamically reversible and independent of the heating and cooling rates. The development and experimental observation of the three crystalline phases relied on different thermal histories. Among the three crystalline phases in CSHET, the K3 phase is the most stable phase, while the K2 and K1 phases are metastable. Note that the K1 phase only formed via a quenching process. Oh the basis of structure sensitive diffraction experiments such as 2D WAXD of oriented samples and SAED of single crystals, detailed structures and molecular packings of these four ordered phases were identified. The LC phase exhibited a hexagonal columnar phase with 2D lattice dimensions ofa = b = 2.38 nm and γ= 120°. All the three crystalline phases possess monoclinic unit cells, yet the y angle is not 90° in the cases of the K2 and the K3 phases, while in the case of the K1 phase the a angle is not 90°.

Synthesis and mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers

Connecting two discotic mesogens via a spacer not only stabilizes the columnar mesophase but also leads to the formation of glass columnar phase, and therefore improves the physical properties of discotic liquid crystals as organic semiconductor. Here, we report the synthesis of eight diacetylene-bridged triphenylene discotic liquid crystal dimers, [C18H6(OCnH2n+1)4(OMe)O2C-C8H16-C≡≡ C-]2, 3(n), (n = 4-8), [C18H6(OC6H13)5O2C-C8H16-C≡≡ C-]2, 6 and [C18H6(OC6H13)5O-(CH2)m-C≡≡ C-]2, 8(m), (m = 1, 3) by Eglinton coupling reaction. The thermotropic liquid crystal properties were studied by differential scanning calorimetry and polarized optical microscopy. The results are showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; dimers 3(n) (n = 5-8) and 6 had glass columnar phase, and no crystallization was observed above -50℃ for all the triphenylene dimers; compared with 3(6), 6 showed higher molecular symmetry, more stable columnar mesophase and wider mesophase range. The connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.

Synthesis of Mixed Tail Triphenylene Discotic Liquid Crystals： Molecular Symmetry and Oxygen-Atom Effect on the Stabilization of Columnar Mesophases

Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would result in novel mesomorphism. A series of mixed tail triphenylenes containing propoxyacetyloxy and alkoxy, abbreviated as C18H6（OCnH2n＋1）3（OCOCH2OC3H7）3, n=4-8, and hexa（propyloxyacetyloxy）triphenylene, C18H6（OCOCH2OC3H7）6 were synthesized. Thermal gravimetry analysis （TGA） of three discogens showed that they had good thermal stability till 350 ℃. The mesomorphism was investigated through differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The preliminary X-ray diffraction （XRD） results of one compound showed that it exhibited ordered hexagonal columnar （Colho） mesophase. These mixed tail triphenylene derivatives possessed much stable Colho mesophase and wider mesophase ranges than their hexaalkoxytriphenylene C18H6（OR）6 and hexaalkanoyloxytriphenylene C18H6（OCOR＇）6 analogues. The asymmetrical compounds 2,6,11-trialkoxy-3,7,10-tri（2-propyloxyacetyloxy）triphenylenes with n=5-8 displayed higher clearing points and wider temperature ranges than their symmetrical isomers 2,6,10-trialkoxy-3,7,11-tri（2-propyloxyacetyloxy）- triphenylenes, while C18H6（OCOCH2OC3H7）6 had the highest clearing point due to the β-oxygen-atom effect.

Synthesis of unsymmetric triphenylene discotic liquid crystals with a semi-fluorinated chain and the influence of fluorophobic effect on mesogenic behavior

The fluorophobic effect of the semi-fluorinated chain of discotic molecules efficiently improves the stability of columnar mesophase.Low symmetric discogens exhibit decreased melting points and wide mesophase ranges.A series of triphenylene derivatives 1,C18H6(OCnH2n+1)4(OMe)(O2CC2H4C6F13),and their hydrocarbon analogues 2,C18H6(OCnH2n+1)4(OMe)(O2CC8H17),n = 4―8,were synthesized for the investigation of the influence of semi-fluorinated peripheral chain and molecular symmetry on mesomorphism.The structures were characterized with 1H NMR and MS.The mesomorphism was studied with differential scanning calorimetry(DSC) and polarizing optical microscopy(POM).The results showed that all triphenylene derivatives exhibited enantiotropic columnar mesophase.The semifluorinated triphenylenes 1a―1e displayed higher melting points and clearing points than their hydrocarbon analogies 2a―2e.Most of them were in columnar mesophase at room temperature.

Theoretical Study on the Charge Transport Properties of Coronene and Its Derivatives

Molecular structures, reorganization energies and charge transport matrix elements of coronene and its fluoro-, hydroxyl- and sulfhydryl-substituted derivatives have been studied at the B3LYP/6-31G＊＊ level. Based on the semi-classical model of electron transfer, charge transport rate constants of the title molecules have been calculated. The results indicate that the coronene molecule is helpful to the transport of negative charge, and the transport rate of positive charge is between those of hexaazatriphenylene and triphenylene.

Mesomorphic Studies on a Series of Nickel (II) Centered Aromatic Complexes Displaying Liquid Crystalline Phases

Two new series (A & B) of three materials each based on the aroyl hydrazinato-nickel (II) complex were synthesized and characterized. The core molecule in these series consists of two 4-benzoyloxy benzylidene moieties and two benzene rings attached at the azomethine moiety. These latter benzene rings have one or two alkoxy chains comprised of either 10, 12, 16 or 18 carbon atoms. The characterization of these two series by polarized optical microscopy and differential scanning calorimetry is described herein. Upon cooling from the Isotropic phase, three of the six materials display a monophasic columnar phase and the other three possess a biphasic nematic and columnar phases. Upon heating, all six materials have a clearance point at high temperatures without displaying mesomorphic behavior. In series B mesogens, it was observed that the longer the hydrocarbon tail length, the lower the clearance point.

Phase Transition Temperature of HPT(2,3,6,7,10,11-hexa-n-pentyloxytriphenylene) from Molecule Dynamic Simulation

Molecule dynamics simulation was used on HPT(2,3,6,7,10,11-hexa-n-pentyloxytriphenylene), which is a discotic Liquid crystal. From analyzing the energy and displacement varying with the temperature, the phase transition temperature of PM6MPP can be predicted. The deviations of T-g, T-m and T-i due to the MD time scale are small enough that it should be possibly used to predict the material properties especially when more powerful computers are available.

Theoretical study on the charge transport properties of triphenylene discogens with a phenylpropionyloxy or 3-phenylpropenoyloxy side chain

Charge transport is one of the most important properties in organic materials.Charge transport properties of triphenylene discogens with a phenylpropionyloxy or 3-phenylpropenoyloxy side chain have been investigated computationally on the basis of semi-classical Marcus theory.The results show that three triphenylene derivatives have high charge mobility.Title compounds have much better electronic mobility than the triphenylene.The triphenylenes containing 3-phenylpropenoyloxy have better hole mobility,but smaller electronic mobility than the triphenylenes with phenylpropionyloxy.For the triphenylene discogens with a phenylpropionyloxy,the longer the alkloxy chains,the better the positive charge transfer rate,but the smaller the negative charge transfer rate.