Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 11: Interfaces and Thin Films I
CPP 11.5: Talk
Monday, March 31, 2014, 17:30–17:45, ZEU 114
Tuning the Monolayer Properties of Liquid Crystalline Septithiophenes — •Khosrow Rahimi1, Wim de Jeu1, Ulrich Ziener2, Martin Möller1, and Ahmed Mourran1 — 1DWI Interactive Materials Research at RWTH Aachen, Germany — 2Institute of Organic Chemistry III, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
Conjugated molecules including oligothiophenes are promising matrials for organic electronic devices due to the combination of low-cost solution processing and charge transport mobility. The conduction in thin polycrystalline films is limitted by the degree of crystallinity and the extent of the crystalline domains. To optimize single crystal devices in monolayers, crystal growth involves the delicate point of decoupling of lateral (two-dimensional) growth from that perpendicular to the substrate. The growth kinetics of molecular thin films will be influenced by possible liquid crystal (LC) order due to anisotropy in molecular structure. New terminally substituted oligothiphenes have been synthesized, that exhibit thermotropic LC phases. They consist of a conjugated thiophene backbone to which long flexible alkyl chains are attached that incorporate a bulky -Si(CH3)- group. Varying the position of -Si(CH3)- in the linear alkyl chain, we find that the temperature window of LC phase is larger when -Si(CH3)- is situated away from the thiophene core. As a result the monodomain size is enhanced. However, this trend is vice versa when the Si group is very close to the core. We conclude that deposition and formation of monolayer and its monodomain size is controlled with LC phase.