LC Chemistry

Session 5B: LC Chemistry
Tuesday, Feb. 14, 2017  14:20-15:40
Chair: Hong-Cheu Lin, National Chiao Tung University, Taiwan
Room: Lecture Hall II
15:10 - 15:25 Paper No.  2017-TUE-S0205-O001
Matthias Lehmann
Free Space in Liquid Crystals – Generation, Design and Application

Free space in condensed matter is usually not present, since the self-assembly in ordered liquid crystals maximises the intermolecular interactions by efficient space filling and nanosegregation in order to minimise the total energy of the system. Nevertheless, there are reports of empty space in columnar LCs. Recently it was demonstrated that deuterated molecules added to LCs are located at sites of lowest density. The aim of our research is the generation of free space in the molecular structure of mesogens and its rational employment for a structural control by filling the void with guests. In these new LC materials the position of the different building blocks should be conductable. Therefore, we focus on shape-persistent star mesogens 1 providing void space between their arms. The core can be a discotic unit such as benzene or phthalocyanine and the arms are conjugated oligomers, which guarantee the shape-persistence. The guests can be bound either via a spacer by covalent bonds or by supramolecular interactions. The rational design leads to filled functional LCs with donors and acceptors double nanosegregated within one column confirmed by comprehensive X-ray scattering studies, modelling, fibre simulation, solid-state NMR, temperature-dependent FT-IR and fluorescence spectroscopy of thin solid films.

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15:25 - 15:40 Paper No.  2017-TUE-S0205-O002
Atsushi Seki
Bulk photovoltaic effect in pi-conjugated ferroelectric liquid crystals

An anomalous photovoltaic (APV) effect in ferroelectrics has attracted interest, due to the potential to generate the open-circuit voltage exceeding the band-gap. This specific phenomenon is caused by the internal electric field originated from spontaneous polarization without any junctions. Recently, we have constructed the pi-conjugated ferroelectric liquid crystal (FLC) system based on phenylterthiophene derivatives. Interestingly, bulk photovoltaic effects were observed in their FLC phases. These compounds exhibited carrier transport properties in FLC phases. However, the details of the specific effect have never been clarified. In this presentation, we consider that the spontaneous polarization and carrier mobilities should be key factors for the APV phenomenon. We provide a detailed study on the correlation between APV effect and those properties in some FLC compounds and the enantiomer mixtures.

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