Selective Reduction of 2-[(Benzoyl)oxy]benzaldehydes without Intramolecular Transesterification
作者:Coleen Pugh
DOI:10.1021/ol005799y
日期:2000.5.1
NaBH4 reduction of 2,5-bis[(4'-(n-alkoxy)benzoyl)oxy]benzaldehydes produces primarily the rearranged phenol, which does not generate liquid crystalline phases when laterally attached to a polymer backbone. Rearrangement is prevented by quenching the intermediate benzyl alkoxide with a weak acid. For example, 2,5-bis[(4'-(methoxy)benzoyl)oxy]benzaldehyde is selectively reduced to 2,5-bis[(4'-(methoxy)benzoyl)oxy]benzyl alcohol with less than 5% intramolecular transesterification using 2-3 equiv of NaBH4 in the presence of 20-30 equiv of acetic acid (1:10 NaBH4/AcOH).
Zhou, Qi-Feng; Li, Hui-Min; Feng, Xin-De, Molecular Crystals and Liquid Crystals (1969-1991), 1988, vol. 155, p. 73 - 82
作者:Zhou, Qi-Feng、Li, Hui-Min、Feng, Xin-De
DOI:——
日期:——
Liquid crystal polymers copolymers and elastomers containing a laterally attached mesogenic unit
作者:Eric A. Whale、Frederick J. Davis、Geoffrey R. Mitchell
DOI:10.1039/jm9960601479
日期:——
The synthesis of a closely-coupled laterally attached side-chain liquid crystal polymer is described. The material exhibits liquid crystalline behaviour over a wide temperature range. Incorporation of non-mesogenic methyl acrylate as a comonomer with the potentially mesogenic monomer results in copolymers which are liquid crystalline, even when the non-mesogenic portion exceeds 60 mol%. Macroscopic alignment can be readily realised in both homopolymer and copolymer samples, either using a magnetic field or by pulling as fibres, and X-ray scattering shows the level of global orientation to be relatively high. Copolymerisation of the mesogenic unit with ca. 10 mol% of hydroxyethyl acrylate results in materials which can be cross-linked by reaction with a diisocyanate. The application of mechanical stress to liquid crystalline elastomers based on this closely coupled unit results in some global orientation of the mesogens, and the stress-strain-orientation behaviour of this cross-linked system is described. Both copolymers and elastomers are compared with liquid crystal polymers in which the mesogen is attached via a terminal linkage.