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Fluorescence study on intermolecular complex formation between mesogenic 4,4′‐biphenyldicarboxylate moieties of thermotropic liquid‐crystalline polyesters with 5 and 6 methylene units
Author(s) -
Huang Hsu Wen,
Horie Kazuyuki,
Tokita Masatoshi,
Watanabe Junji
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980901)199:9<1851::aid-macp1851>3.0.co;2-s
Subject(s) - mesogen , thermotropic crystal , intermolecular force , fluorescence , polyester , liquid crystal , phase (matter) , chemistry , crystallography , methylene , photochemistry , materials science , molecule , organic chemistry , liquid crystalline , optics , physics , optoelectronics
The change in intermolecular complex formation between mesogenic 4,4′‐biphenyldicarboxylate moieties of thermotropic liquid‐crystalline (LC) polyesters containing 5 and 6 methylene units (BB‐ n , n = 5, 6) was studied by fluorescence technique. BB‐5 shows a crystalline, an S CA , and an isotropic phase during heating. BB‐6 shows a crystalline mixture of β‐ and γ‐phase, a pure γ‐phase, an S A , and an isotropic phase during heating. The fluorescence of BB‐ n is confirmed to be due to the formation of an intermolecular ground‐state complex between two mesogenic 4,4′‐biphenyldicarboxylate moieties, and shows a wavelength shift of the fluorescence peak to lower wavelengths upon heating. This is because the increase in thermal fluctuation with increasing temperature induces a decrease in interaction between two 4,4′‐biphenyldicarboxylate moieties. Because of the constancy of the fluorescence peak wavelength in the LC phase of BB‐ n , LC phases for S CA and S A type molecular arrangements of the LC polyester with mesogenic biphenyl moieties were proved to show fluorescence around 376 and 360 nm, respectively. However, the shift of the fluorescence peak wavelength to lower wavelengths upon heating has been observed for the first time in the present study. The change in molecular interaction between the mesogenic moieties of the LCPs during heating is shown to result in various fluorescence patterns.