Using steady-state and time-resolved fluorescence spectroscopy, we investigated the intermolecular coupling between mesogenic biphenyl-ester moieties of a thermotropic liquid crystal under phase transition. In the crystalline-to-smectic C transition, a broad excitation band centered at 280 nm and a fluorescence redshift by 25 nm, followed by a drastic change in the fluorescence time-decay constant (from ∼90 to ∼230 ps), are consistently observed. These changes result from the intermolecular configurational change from biphenyl-biphenyl to biphenyl-ester. Emissions from intermolecular complexes such as J-aggregated biphenyls in crystalline and biphenyl-ester exciplexes in smectic C, smectic A, and isotropic phases are characterized.
Bibliographical noteFunding Information:
We appreciate Dr. M. Lee for providing the rod-coil molecules. This research was financially supported by the APRI Research Program of GIST, from the Basic Science Research Program . Financial support was provided through the National Research Foundation funded by the Korea government (Ministry of Education, Science and Technology , No. 2011-0006563 ), and through the EI Project ARQ20114000114 ( 401-112-014 ) funded by the Korea Ministry of Environment . Y.-R. Kim expresses thanks for the grant from the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare and Family Affairs (Grant No. A121133 ).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry