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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 27, Number 1
BKCSDE 27(1)
January 20, 2006 

Conformational Study of Liquid Crystalline Polymer: Theoretical Studies
Mi Jung Lee, Dong Hee Kim*
Liquid crystalline, Conformation, 13C chemical shift, Calculation
The relaxed torsional potential of a liquid crystalline polymer containing an ester functional group in a mesogenic unit (hereafter 12-4 oligomer) has been calculated with the ab initio self-consistent-field using 6- 31G* basis set. GIAO 13C NMR chemical shifts also have been calculated at the B3LYP/6-31G* level of theory for each conformational structure obtained from torsional potential calculation. The results show that the phenyl ring-ester linkages are coplanar with the dihedral angle of about 0° and the ring-ring linkages in the biphenyl groups are tilted with the dihedral angle of around 43-44° in the lowest energy conformer. The biphenyl ring has a comparatively lower energy barrier of internal rotation potential in the ring-ring than that of phenyl ring-ester. The 13C chemical shifts of carbonyl carbons were found to move to upfield due to π - conjugation with phenyl ring and slightly affected about 0.5 ppm by dihedral angle of the ring-ring linkage.
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