Mesophase Transition of Series Materials Containing Fluorene, Fluorenone and Biphenyl Structures with Chiral End Groups

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Abstract
S 2-alkoxyfluorene-7-carboxylic acid 4-(2-methylbutoxy)-phenyl ester and S 2-alkoxyfluorenone-7-carboxylic acid 4-(2-methylbutoxy)-phenyl ester were synthesized and the effects of mesogen modification or substitution of biphenyl with fluorene and fluorenone group in a mesogen core were studied to obtain a wide temperature range for the SmC* phase. It was found that the SmA phase was rather stabilized by a fluorene substitution, though the thermal stability of the SmC* phase decreased in comparison with the data for biphenyl derivatives. On the other hand, by a fluorenone substitution the SmA phase stability decreased markedly and the SmC* phase stability increased. These results could be explained by two factors. 1. Enhancement in attractive intermolecular force by increasing polarizability of fluorene, compared with biphenyl. 2. Enhancement in induction force due to the dipole moment of the carbonyl group in the fluorenone.

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