Abstract
Intermolecular complex formation between mesogenic terphenyldiimide moieties of a thermotropic liquid-crystalline (LC) polyimide (P-11TPE) was studied by steady-state fluorescence and fluorescence lifetime measurements together with differential scanning calorimetry (d.s.c.) and wide-angle X-ray diffraction (WAXD). The P-11TPE shows various highly-ordered crystalline phases and a smectic phase during heating, according to the d.s.c. and WAXD results. By comparing the fluorescence spectra and fluorescence lifetimes between P-11TPE and its model compound ( N, N′-diundecylter-phenyldiimide), the fluorescing complex at 438 nm of P-11TPE is confirmed to be an intermolecular ground-state complex between two terphenyldiimide moieties. The fluorescence peak wavelength of this intermolecular complex shifts slightly to shorter wavelength below the glass transition temperature and shifts abruptly to longer wavelength around crystallization, then shifts gradually to shorter wavelength again from various crystalline phases until the isotropic phase. The changes in fluorescence intensity and fluorescence lifetime around phase transition temperatures are also observed. These apparent changes in fluorescence behaviour indicate the differences in the nature and number of intermolecular complexes and radiationless deactivation processes in various phases. The characteristics of fluorescence behaviour for P-11TPE are also compared to those for various LC polyesters studied previously, and it is concluded that the red shift of fluorescnece is due to the apparent change in molecular arrangement between mesogenic moieties and the blue shift of fluorescence is due to the almost identical packing pattern with increasing thermal fluctuation during phase transition for liquid crystal polymers. By using fluorescence technique, molecular interaction between mesogenic moieties of liquid crystal polymer has been proved to show various patterns of changes during phase transition processes.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
