Influence of liquid crystalline polymer and recycled PET as minor blending components on rheological behavior,morphology, and thermal properties of thermoplastic blends

In this study, the potential of recycled poly(ethylene terepthalate) (rPET) as a well‐defined reinforcing material for the in situ microfibrillar‐reinforced composite (iMFC) was investigated in comparison with that of liquid crystalline polymer (LCP). Each dispersed phase (LCP or rPET) was melt blended with high density polyethylene (PE) by using extrusion process. The rheological behavior, morphology, and the thermal stability of LCP/PE and rPET/PE blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of LCP or rPET into PE significantly improved the processability. A potential of rPET as a processing lubricant by bringing down the melt viscosity of the blend system was as good as LCP. The elongated LCP domains were clearly observed in as‐extruded strand. Although the viscosity ratio of the rPET/PE system was lower than that of the LCP/PE blend system, most rPET domains appeared as small droplets. An addition of LCP and rPET into the PE matrix improved the thermal resistance significantly in air but not in nitrogen. The obtained results suggested the high potential of rPET as a processing aid and good thermally resistant material similar to LCP. Copyright © 2009 John Wiley & Sons, Ltd.     

Self-assembly of cyclic hexamers of γ-cyclodextrin in a metallosupramolecular framework with d-penicillamine

Cyclodextrins are widely used cyclic oligosaccharides of d-glucose whose hydrophilic exterior is covered by hydroxyl groups and whose hydrophobic interior is surrounded by lipophilic moieties. Because of this structural feature, cyclodextrin molecules commonly aggregate into dimensional structures via intermolecular hydrogen bonds, and their aggregation into closed oligomeric architectures has been achieved only via the attachment of functional substituent groups to the cyclodextrin rings. Here, we report the first structurally characterized self-assembly of non-substituted γ-cyclodextrin molecules into cyclic hexamers, which was realized in a chiral coordination framework composed of complex-anions with d-penicillamine rather than l- or dl-penicillamine. The self-assembly is accompanied by the 3D-to-2D structural transformation of porous coordination frameworks to form helical hexagonal cavities that accommodate helical γ-cyclodextrin hexamers. This finding provides new insight into the development of cyclodextrin chemistry and host–guest chemistry based on chiral recognition and crystal engineering processes.

The complex anions with d-penicillamine are organized into a 3D porous framework that allows the inclusion of γ-CD. The inclusion is accompanied by the 3D-to-2D transformation of porous frameworks so as to accept cyclic hexamers of γ-CD.     

Changes in ferroelectric properties of lead indium niobate-lead titanate ceramics under compressive stress applied perpendicular to an electric field

The influences of perpendicular compressive stress on the ferroelectric properties of (1−x)Pb(In_1/2Nb_1/2)O₃-xPbTiO₃ (x=0.1-0.4) ceramics were investigated in this study. In general, with increasing compressive stress the coercive field and the dissipation energy of the ceramics were seen to increase. The stress-induced changes in the polarization, however, depended significantly on ceramic compositions. The observations were mainly interpreted in terms of competing influence of the domain switching through non-180° domain walls, clamping of domain walls, and the stress-induced decrease in the switchable part of spontaneous polarization.     

Room temperature synthesis of Ti-SBA-15 from silatrane and titanium-glycolate and its catalytic performance towards styrene epoxidation

A novel room temperature sol–gel synthesis of Ti-SBA-15 is described using moisture stable silatrane and titanium glycolate precursors, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (EO₂₀PO₇₀EO₂₀) as the structure directing agent. Catalyst performance was optimized by systematically investigating the influence of acidity, reaction time and temperature, and titanium loading. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) showed well-ordered 2D mesoporous hexagonal structures, while N₂ adsorption/desorption measurements yielded high surface areas (up to 670 m²/g), with large pore diameters (5.79 nm) and volumes (0.83 cm³/g). Diffuse reflectance UV–visible spectroscopy (DRUV) was found that tetravalent titanium as Ti⁴⁺O₄ tetrahedra were incorporated in the framework through displacement of Si⁴⁺O₄ after calcination (550°C/6 h) to loadings of 7 mol% Ti without perturbation of the ordered mesoporous structure, or decoration by extra-framework anatase containing Ti⁴⁺O₆ octahedra. The catalytic activity and selectivity of styrene epoxidation using hydrogen peroxide (H₂O₂) showed that the conversion of styrene increases significantly at higher titanium contents. The only products of this reaction were styrene oxide and benzaldehyde, with selectivity of 34.2 and 65.8%, respectively, at a styrene conversion of 25.8% over the 7 mol% Ti-SBA-15 catalyst. Beyond this titanium loading, anatase is deposited on the framework and catalytic activity degrades. The performance of the new catalyst is also shown to be superior to conventional materials produced by incipient wetness impregnation where Ti resides on the surface of SBA-15, giving a styrene conversion of 11.9% under identical reaction conditions.