Phase behaviour and electro-optical response of systems composed of nematic liquid crystals and poly (2-ethylhexylacrylate)

Abstract

Experimental studies of phase diagram and morphology of mixtures composed of linear poly(2-ethylhexylacrylate) (poly-2EHA) of molecular weight M w =92000g/mol and E7, an eutectic blend of nematic liquid crystals (LCs), were performed. The latter consists of four cyanoparaphenylenes i.e. 4-cyano-4'-n-pentyl-biphenyl (5CB), 4-cyano-4'-n-heptyl-biphenyl (7CB), 4-cyano-4'-n-oxyoctyl-biphenyl (8OCB), and 4-cyano-4''-n-pentyl-p-biphenyl (5CT).Thermal properties of the poly-2EHA/E7 system were studied by differential scanning calorimetry and the sample morphologies were investigated by optical microscopy. Phase diagram analysis revealed an increase of the nematic-isotropic transition temperature when E7 was added to poly-2EHA, compared to pure E7. This effect, related to a preferential miscibility phenomenon of E7 components towards poly-2EHA, was evidenced by gas chromatography analysis coupled to mass spectrometry (GC-MS), allowing to qualify and quantify the content of phase separated LC domains.Thermograms of model LC mixtures including 5CB, 7CB, 8OCB and 5CT, which correspond to their composition in segregated LC domains of poly-2EHA/E7, present strong deviations from eutectic behavior. In order to access the impact of such variations for practical applications, such a model LC mixture was introduced in photochemically crosslinked 2-EHA (polycross-2EHA). Surprisingly, the electro-optical response of the obtained polycross-2EHA/LC films was considerably improved compared to the original polycross-2EHA/E7 system.

Fullerene-Based Nanosurfactant for the Automatic Homeotropic Alignment of Liquid Crystals

“…Subsequently, the temperature cooled down to room temperature (nematic phase) after injection. 22 The DLC/LC and C 60 /LC mixtures show a Schlieren texture, which is commonly observed in the nematic phase in the planar alignment (PA) anchoring condition. 23 Of course, the only host LC molecules in the cell show a typical Schlieren texture at room temperature (Figure S1).…”

“…To obtain the precise element information of the protrusions, X-ray photoelectron spectroscopy (XPS) analysis was performed (Figure c,d). Notably, any binding energy peak, corresponding to CN in a cyanobiphenyl group of the host LC molecule, was not observed, indicating that the host LC is well removed and is not present in the protrusions . The major elements present in C 60 were identified by the O1s and C1s peaks (Figure c).…”

“…Notably, any binding energy peak, corresponding to C�N in a cyanobiphenyl group of the host LC molecule, was not observed, indicating that the host LC is well removed and is not present in the protrusions. 22 The major elements present in C 60 were identified by the O1s and C1s peaks (Figure 4c). In the vertically aligned (VA) mode of liquid crystal displays (LCDs), the LC molecules have HA and the brightness of negative liquid crystal displays is controlled by inducing the applied electric field.…”

“…DLC and 0.05 wt % C 60 were mixed with the host LC at isotropic temperature ( T ni = 75 °C), and the homogeneous LC mixtures were injected into an indium tin oxide (ITO)-coated sandwich cell fabricated by 10 μm spacers. Subsequently, the temperature cooled down to room temperature (nematic phase) after injection . The DLC/LC and C 60 /LC mixtures show a Schlieren texture, which is commonly observed in the nematic phase in the planar alignment (PA) anchoring condition .…”

Ultra-stable liquid crystal droplets coated by sustainable plant-based materials for optical sensing of chemical and biological analytes

“…The small nematic temperature window of the commonly used LC, such as nematic, 4-cyano-4′-pentylbiphenyl (5CB) (18–35 °C) restricts their use in clinical settings. 14 Hence, a nematic LC mixture, E7, with a wide nematic range between −62 to +61 °C 30 was purchased from Synthon Chemicals GmbH & Co. KG (Bitterfeld-Wolfen, Germany). E7 consists of four nematic cyanoparaphenylene LCs, i.e.…”