Nematic liquid crystal/clay mineral composites

Influence of hydroquinone content on thermotropic liquid crystalline copolymers and nanocomposites: thermo-mechanical properties and morphology

Thermotropic liquid crystalline copolyesters (Co-TLCPs) were synthesized by varying the hydroquinone (HQ) molar ratio from 1–5 with respect to the 2,5-diethoxyterephthalic acid (ETA) monomer. The thermal properties and liquid crystalline mesophases of the synthesized Co-TLCP were investigated. All of the Co-TLCPs synthesized using a HQ molar ratio of 1–5 showed a nematic liquid crystalline phase. Among the Co-TLCPs obtained using HQ in various molar ratios, the most stable physical properties and a clear liquid crystalline phase were obtained when HQ was 4 mol. Among the various Co-TLCPs synthesized, hybrids were prepared using Co-TLCP synthesized with a 1 : 4 = ETA : HQ ratio and organoclay. A 1–10% loading of the organoclay Cloisite 93A was employed per weight of TLCP, and the clay was dispersed using the melt intercalation method. Among the Co-TLCP hybrids, the morphology and thermal properties of the hybrids were investigated according to the changes in the Cloisite 93A in the 1–10 wt% range. In general, the thermal properties were superior when the organoclay loading was 3 wt% and were inferior when the organoclay amount was 5 wt% or more. This result was confirmed by the dispersibility of the clay through transmission electron microscopy.

Thermotropic liquid crystalline copolyesters (Co-TLCPs) were synthesized by varying the hydroquinone (HQ) molar ratio from 1–5 with respect to the 2,5-diethoxyterephthalic acid (ETA) monomer.

Supramolecular exfoliation of layer silicate clay by novel cationic pillar[5]arene intercalants

Clays are multi-layered inorganic materials that can be used to prepare nanocomposite fillers. Because the multi-layered structure is thermodynamically stable, it is difficult to change a multi-layered material into single layers to improve its dispersity. Previously, clays were modified with dodecylammonium cations to promote complexation with nylon 6, nylon 66, polypropylene, polyethylene, polystyrene, and polycaprolactone to increase the mechanical strength (and/or thermal stability) of the composite material; however, complete exfoliation could not be achieved in these composites. In this study, pillar[5]arenes are synthesized and functionalized with ten cationic substituents as novel intercalants for modifying bentonite clay, which is a multi-layered metal-cation-containing silicate. The pillar[5]arenes exfoliate the clay by forming polyrotaxanes with poly(ethylene glycol) through host–guest interactions.