High charge-carrier mobility in pi-deficient discotic mesogens: design and structure-property relationship.
Hexaazatrinaphthylene (HATNA) derivatives with six alkylsulfanyl chains of different length (hexyl, octyl, decyl and dodecyl) have been designed to obtain new potential electron-carrier materials. The electron-deficient nature of these compounds has been demonstrated by cyclic voltammetry. Their thermotropic behaviour has been studied by means of differential scanning calorimetry and polarised optical microscopy. The supramolecular organisation of these discotic molecules has been explored by temperature-dependent X-ray diffraction on powders and oriented samples. In addition to various liquid crystalline columnar phases (Col(hd), Col(rd)), an anisotropic plastic crystal phase is demonstrated to exist. The charge-carrier mobilities have been measured with the pulse-radiolysis time-resolved microwave-conductivity technique. They are found to be higher in the crystalline than in the liquid crystalline phases, with maximum values of approximately 0.9 and 0.3 cm(2) V(-1) s(-1), respectively, for the decylsulfanyl derivative. Mobilities strongly depend on the nature of the side chains.
Lehmann
Matthias
M
Laboratoire de Chimie des Polymères, CP 206/1, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium. matthias.lehmann@chemie.tu-chemnitz.de
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Gómez Aspe
Rafael
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Buess-Herman
Claudine
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Koch
Michel H J
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Debije
Michael G
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Piris
Jorge
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de Haas
Matthijs P
MP
Warman
John M
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Watson
Mark D
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Lemaur
Vincent
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Cornil
Jérôme
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Geerts
Yves Henri
YH
Gearba
Raluca
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Ivanov
Dimitri A
DA