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An old dog with new tricks: Schiff bases for liquid crystals materials based on isoxazolines and isoxazoles.
Author(s) -
Fritsch Luma,
Merlo Aloir A.
Publication year - 2016
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201500044
Subject(s) - mesophase , thermal decomposition , chemistry , liquid crystal , thermal stability , aniline , polymer chemistry , homologous series , organic chemistry , crystallography , materials science , phase (matter) , optoelectronics
Schiff bases are in action again showing an exuberant mesophase range despite their chemical and thermal weakness. Two series of Schiff bases (SB), based on isoxazolines 9 a–f and isoxazoles 10 a–f , are described. 9 a–f were synthesized by a [3+2] cycloaddition 1,3‐dipolar of arylnitrile oxide from p ‐nitrobenzaldehyde ( 1 ) and alkenes. And, subsequently oxidized to 10 a–f by MnO 2 . The isoxazolines and isoxazoles thus obtained were reduced to aniline derivatives and condensed with appropriated arylaldehydes. The SBs series isoxazolines 9 a–f presented a narrow mesophase range, while SBs series isoxazoles 10 a–f showed a large mesophase range. Nematic mesophase was observed for SBs with short and non‐polar groups, while SmA and SmC mesophase for SBs with long and more polar terminal groups. The stability of the SBs is also dependent on the clearing temperature. For 10 a–f with high clearing temperature, decomposition induced by heat was observed during the first cycle of heating and in solutions of CDCl 3 . Series 9 a–f was more resistant to the thermal decomposition.