Cyanobiphenyl versus Alkoxybiphenyl: Which Mesogenic Unit Governs the Mesomorphic Properties of Guanidinium Ionic Liquid Crystals?
作者:Johannes Christian Haenle、Manuel M. Neidhardt、Stuart Beardsworth、Jochen Kirres、Angelika Baro、Sabine Laschat
DOI:10.1071/ch14376
日期:——
the phenyl ring revealed decreased melting and clearing points for the bent cationicheadgroup. All guanidinium ionicliquidcrystals 3 displayed only smectic A (SmA) phases. A packing model is assumed where the molecules in a bilayer stack over each other in opposite direction with interdigitated terminal decyloxy groups and spacers.
A novel chiral-photochromic side-chain polyacrylate with azobenzene fragments in the side groups has been synthesised. It was shown that the polymer forms a smectic phase and a cholesteric supramolecular helical structure with selective light reflection in IR spectral range. Thin spin-coated films of the polymer were prepared and their photooptical and chirooptical properties were studied in detail. It was found that UV irradiation of the films led to E-Z isomerization of the azobenzene moieties with high conversion, which is dependent on thermal prehistory of the films. Subsequent action of visible light results in partial recovery of the E-isomer content, whereas annealing leads to the full back conversion. Circular dichroism (CD) measurements revealed formation of the helical supramolecular structure even in the initial spin-coated polymer films. The E-Z isomerization induces complete disruption of helical order in non-annealed films of the polymer, whereas in the smectic phase of the annealed film only a significant decrease in CD values was found. In addition, the photoorientation phenomena induced by polarized light were studied. It was shown that polarized light induces linear dichroism in the films provided by azobenzene group orientation and the dichroism is stable at room temperature for a prolonged time. These combined chirooptical and photooptical features of this novel polymer enable one to consider this multifunctional compound as a promising material for photonics and for optical applications.