Transient photoconductivity in a discotic hexagonal plastic crystal

Simmerer, J.; Glüsen, Andreas; Paulus, Wolfgang; Kettner, A.; Schuhmacher, Peter; Adam, Dieter; Etzbach, Karl-Heinz; Siemensmeyer, K.; Wendorff, Joachim H.; Ringsdorf, Helmut; Haarer, D.

doi:10.1002/adma.19960081010

Cited by 237 publications

(148 citation statements)

References 25 publications

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“…Since columnar discotic liquid crystals (LCs) show many extraordinary properties such as one-dimensional (1D) electrical conductivity, 2-5 fast photoconductivity [6][7][8][9][10][11] and ferroelectricity, 12,13 the structures and dynamics of discotic LCs have been studied extensively. Traditional columnar phases are normally constructed with discogenic (disc-like) molecules as building blocks which possess a rigid core with flexible tails (most of them are alkyl chains), and they usually exhibit three-, four-or six-fold rotational symmetry.…”

Section: Introductionmentioning

confidence: 99%

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

et al. 2006

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A series of symmetrically tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamides (CnPhBA, where n is the number of carbon atoms in the alkyl chains, n = 10, 12 and 16), was synthesized in order to investigate the effect of alkyl chain length on supra-molecular ordered structures induced by hydrogen (H)-bonding and micro-phase separation. These bisamides consist of a rigid aromatic bisamide core with three flexible alkyl chains at each end of the core. Major phase transitions and their origins in CnPhBA bisamides were studied with differential scanning calorimetry, one-dimensional (1D) wide angle X-ray diffraction (WAXD), infrared spectroscopy, and solid-state carbon-13 nuclear magnetic resonance experiments. The structures of these compounds in different phases were identified using 2D WAXD from oriented samples and were also confirmed by selected area electron diffractions in transmission electron microscopy from stacked single crystals and by computer simulations. All of the CnPhBA bisamides in this series formed a highly ordered oblique columnar (W OK ) phase and a low-ordered oblique columnar (W OB ) phase, similar to a recent report on C14PhBA.1 The two main driving forces in the formation of these two supra-molecular columnar structures were identified: One was the H-bond formation between N-H and CLO groups, and the other was the micro-phase separation between the bisamide cores and the alkyl chains. With increasing the length of alkyl tails, the isotropization temperature decreased, while the disordering temperature of the alkyl tails increased. The 2D lattice structures perpendicular to the columnar axis also increasingly deviated from the pseudohexagonal packing with increasing the alkyl tail length. However, the alkyl tail length did not have a significant influence on the packing along the columnar axis direction. Utilizing polarized optical microscopy, the phase identifications were also supported by the observation of texture changes and molecular arrangements inside of the micro-sized domains.

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Section: Introductionmentioning

confidence: 99%

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

et al. 2006

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“…This is a reasonable assumption based on the steric hindrance created by the bulky side chains. [24] This phase is designated as columnar tetragonal crystal plastic phase [25] since no regular position of atoms can be deduced from GIXD images or sXRD patterns but rather the center of mass of molecules are located on a regular lattice. Now that the structure of the substrate-induced phase has been determined, we turn to the intriguing question of why it does form.…”

Section: Doi: 101002/adma201103739mentioning

confidence: 99%

Substrate‐Induced Crystal Plastic Phase of a Discotic Liquid Crystal

et al. 2011

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A new phase of a known discotic liquid crystal is observed at the interface with a rigid substrate. The structure of the substrate-induced phase has been characterized by atomic force microscopy, specular X-ray diffraction, and small-angle and wide-angle grazing incidence X-ray diffraction. The substrate-induced phase, which has a thickness of ∼30 nm and a tetragonal symmetry, differs notably from the bulk phase. The occurrence of such phase casts a new light on alignment of discotic liquid crystals.

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“…The carrier transport characteristics in these three phases in hexaalkoxytriphenylene and hexaalkylthiotriphenylene derivatives are studied by the TOF technique, as shown in Figure 2. 49 The hole mobility in the columnar disordered phase is on the order of 10 À3 cm 2 V À1 s À1 ; 30,31 however, it increases to a value on the order of 10 À2 cm 2 V À1 s À1 in the plastic phase, which has a more closely stacked structure than the disordered phase. 51 The hole mobility in the helical phase of hexahexylthiotriphenylene in which a crystal-like long-range molecular order exists within the columns, [30][31][32] increases to 0.1 cm 2 V À1 s À1 ; this is comparable to the hole mobility in molecular crystals.…”

Section: The Bulk Carrier Transport Character-istics In the Liquid Crmentioning

confidence: 99%

“…44 The drift mobility in these phases, which was determined to be in the range of 10 À4 -10 À1 cm 2 V À1 s À1 by the TOF technique, was found to be strongly affected by the structure of the liquid crystal phase. 49,50 The relationship between the carrier transport characteristics and structures of the columnar phases of triphenylene derivatives 49 and those of the smectic phases of 2-phenylnaphthalene and terthiophene derivatives was studied by the TOF method. 50 Three typical columnar phases present in triphenylene derivatives are shown in Figure 2.…”

Section: The Bulk Carrier Transport Character-istics In the Liquid Crmentioning

confidence: 99%

Development of Liquid-Crystalline Semiconductors with High Carrier Mobilities and Their Application to Thin-film Transistors

Funahashi

2009

Polym. J.

130

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Carrier transport in liquid-crystal phases, design of liquid-crystalline semiconductors with high carrier mobilities, and their application to field-effect transistors are reviewed. High carrier mobility has been observed in the smectic phases of oligothiophene derivatives as well as in the columnar phases of triphenylene and hexabenzocoronene derivatives. The mobility increases with the molecular ordering in the mesophases and extension of the -conjugated system of the liquidcrystal molecules. Asymmetrically substituted liquid-crystalline oligothiophene derivatives retain the highly ordered smectic phases below room temperature. The liquid crystals are solution-processable and can be used in high-performance field-effect transistors. The transistors exhibit high hole mobility and on/off ratio of 4 Â 10 À2 cm 2 V À1 s À1 and 10 7 , respectively.

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Transient photoconductivity in a discotic hexagonal plastic crystal

Cited by 237 publications

References 25 publications

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Substrate‐Induced Crystal Plastic Phase of a Discotic Liquid Crystal

Development of Liquid-Crystalline Semiconductors with High Carrier Mobilities and Their Application to Thin-film Transistors

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