Nematic liquid crystals(NLCs),that is,fluids with optical anisotropy as well as electric-and magnetic-field responsiveness,have been widely used in commercial liquid crystal displays.Recent advancements have extended ...Nematic liquid crystals(NLCs),that is,fluids with optical anisotropy as well as electric-and magnetic-field responsiveness,have been widely used in commercial liquid crystal displays.Recent advancements have extended the scope of NLC molecules to large calamiticπ-conjugated systems,which heralds prospects for novel applications that exploit their superior electronic or optical functionalities in,for example,electric field controlled fluorescence switch devices.However,NLC phases of such extendedπ-systems usually flow only at high temperatures,which hampers device applications that operate around room temperature.Here,we show near-room-temperature NLCs of aπ-conjugated fluorophore by introducing a flexible cyclic structure into the mesogenic core.3,8-Bis(4-propylphenyl)-6,7-dihydro-5H-benzo[7]annulene(DPB[7]-C3)has a nematic phase in a significantly lower temperature range(52.6-160.4◦C)than the DPB[7]-C3 analog without flexible alkylene bridges,(E)-4-propyl-4′-(4-propylstyryl)-1,1′-biphenyl(248-262◦C).We attribute this large decrease in the phase transition temperature to large intramolecular conformational entropies that arise from the geometric change of the cyclic structure,which involves rotational motion of single biaryl-bonds and bending motions along the long molecular axis in the thermal equilibrium state.The practical utility of these NLC molecules is demonstrated by preparing an electric-fieldresponsive large-area fluorescent switch device with a sub-millisecond response time from a mixture of 3,8-bis(4-alkylphenyl)-6,7-dihydro-5H-benzo[7]annulenes(DPB[7]-Cns).展开更多
Supramolecular liquid crystals(SLCs)are attractive materials for fabricating devices with new optoelectronic functions.Conventional SLCs are made from hydrogen-bonded mesogens.However,these mesogens suffer from high m...Supramolecular liquid crystals(SLCs)are attractive materials for fabricating devices with new optoelectronic functions.Conventional SLCs are made from hydrogen-bonded mesogens.However,these mesogens suffer from high melting points,and the types of formable aggregates are limited owing to the directionality of the hydro-gen bonding.Therefore,to fabricate non-hydrogen-bonded SLCs,we hypothesized that the introduction of tertiary amide groups into calamitic molecules would be advantageous because they have an L-shaped structure with N-or C-alkyl side chains not aligned along the long axis and theflexibility to undergo cis–trans isomeriza-tion.In this study,we developed a novel non-hydrogen-bonded SLC by assembling an L-shaped dimer composed of calamitic molecules(phenyltolanes)with tertiary amides at their ends.These molecules exhibited a smectic B phase.The phase tran-sition temperature of the SLCs from crystal to liquid crystal phase was low despite the longπ-conjugated core.Wide-angle X-ray diffraction and variable-temperature Fourier-transform infrared measurements revealed dimer formation by weak inter-molecular interactions,that is,the molecular recognition of L-shaped molecules,and mobility of the alkyl groups attached to amide driven by cis–trans isomerization in the liquid crystal phase.Thus,cis–trans isomerization of tertiary amides contributed enormously to the formation and lower clearing points of this SLC.The developed method can be used not only to develop non-hydrogen-bonded SLCs but also to develop novel soft matter with controlled properties by incorporating the SLCs,as the aggregates can be controlled to impart desired functionalities.展开更多
基金supported in part by MEXT/JSPS KAKENHI grants 21J22016(RI),22KJ1276(RI),23H01935(TS)23H02036(GK),17H05145(GK),MEXT Leading Initiative for Excellent Young Researchers(HY),JST PRESTO(GK)the Research Program of Network Joint Research Center for Materials and Devices(Kyushu University)(KI),Toshiaki Ogasawara Memorial Foundation(GK),Iketani Science and Technology Foundation,and Murata Science and Education Foundation(GK).
文摘Nematic liquid crystals(NLCs),that is,fluids with optical anisotropy as well as electric-and magnetic-field responsiveness,have been widely used in commercial liquid crystal displays.Recent advancements have extended the scope of NLC molecules to large calamiticπ-conjugated systems,which heralds prospects for novel applications that exploit their superior electronic or optical functionalities in,for example,electric field controlled fluorescence switch devices.However,NLC phases of such extendedπ-systems usually flow only at high temperatures,which hampers device applications that operate around room temperature.Here,we show near-room-temperature NLCs of aπ-conjugated fluorophore by introducing a flexible cyclic structure into the mesogenic core.3,8-Bis(4-propylphenyl)-6,7-dihydro-5H-benzo[7]annulene(DPB[7]-C3)has a nematic phase in a significantly lower temperature range(52.6-160.4◦C)than the DPB[7]-C3 analog without flexible alkylene bridges,(E)-4-propyl-4′-(4-propylstyryl)-1,1′-biphenyl(248-262◦C).We attribute this large decrease in the phase transition temperature to large intramolecular conformational entropies that arise from the geometric change of the cyclic structure,which involves rotational motion of single biaryl-bonds and bending motions along the long molecular axis in the thermal equilibrium state.The practical utility of these NLC molecules is demonstrated by preparing an electric-fieldresponsive large-area fluorescent switch device with a sub-millisecond response time from a mixture of 3,8-bis(4-alkylphenyl)-6,7-dihydro-5H-benzo[7]annulenes(DPB[7]-Cns).
基金Japan Science and Technology Agency,Grant/Award Number:JPMJPR1096Japan Society for the Promotion of Science,Grant/Award Numbers:17H05145,23H02036Izumi Science and Technology Foundation。
文摘Supramolecular liquid crystals(SLCs)are attractive materials for fabricating devices with new optoelectronic functions.Conventional SLCs are made from hydrogen-bonded mesogens.However,these mesogens suffer from high melting points,and the types of formable aggregates are limited owing to the directionality of the hydro-gen bonding.Therefore,to fabricate non-hydrogen-bonded SLCs,we hypothesized that the introduction of tertiary amide groups into calamitic molecules would be advantageous because they have an L-shaped structure with N-or C-alkyl side chains not aligned along the long axis and theflexibility to undergo cis–trans isomeriza-tion.In this study,we developed a novel non-hydrogen-bonded SLC by assembling an L-shaped dimer composed of calamitic molecules(phenyltolanes)with tertiary amides at their ends.These molecules exhibited a smectic B phase.The phase tran-sition temperature of the SLCs from crystal to liquid crystal phase was low despite the longπ-conjugated core.Wide-angle X-ray diffraction and variable-temperature Fourier-transform infrared measurements revealed dimer formation by weak inter-molecular interactions,that is,the molecular recognition of L-shaped molecules,and mobility of the alkyl groups attached to amide driven by cis–trans isomerization in the liquid crystal phase.Thus,cis–trans isomerization of tertiary amides contributed enormously to the formation and lower clearing points of this SLC.The developed method can be used not only to develop non-hydrogen-bonded SLCs but also to develop novel soft matter with controlled properties by incorporating the SLCs,as the aggregates can be controlled to impart desired functionalities.
