Mercapto-Functionalized Porous Organosilica Monoliths Loaded with Gold Nanoparticles for Catalytic Application.

Porous organosilica monoliths have attracted much attention from both the academic and industrial fields due to their porous structure; excellent mechanical property and easily functionalized surface. A new mercapto-functionalized silicone monolith from a precursor mixture containing methyltrimethoxysilane; 3-mercaptopropyltrimethoxysilane; and 3-mercaptopropyl(dimethoxy)methylsilane prepared via a two-step acid/base hydrolysis-polycondensation process was reported. Silane precursor ratios and surfactant type were varied to control the networks of porous monolithic gels. Gold nanoparticles were loaded onto the surface of the porous organosilica monolith (POM). Versatile characterization techniques were utilized to investigate the properties of the synthesized materials with and without gold nanoparticles. Scanning electron microscopy was used to investigate the morphology of the as-synthesized porous monolith materials. Fourier transform infrared spectroscopy was applied to confirm the surface chemistry. 29Si nuclear magnetic resonance was used to investigate the hydrolysis and polycondensation of organosilane precursors. Transmission electron microscopy was carried out to prove the existence of well-dispersed gold nanoparticles on the porous materials. Ultraviolet-visible spectroscopy was utilized to evaluate the high catalytic performance of the as-synthesized Au/POM particles.

Flame-Retardant Properties and Mechanism of Polylactic Acid-Conjugated Flame-Retardant Composites.

The DOPO derivative-conjugated flame retardant 4, 4'-{1'', 4'' - phenylene - bis [amino - (10‴ - oxy -10‴-hydro-9‴-hydrogen-10‴ λ5 -phosphaphenanthrene-10''-yl)-methyl]}-diphenol (P-PPD-Ph) with two hydroxyl groups was synthesized. Polylactic acid conjugated flame-retardant composites with P-PPD-Ph were papered by using a twin-screw extruder. The flame-retardant properties of polylactic acid-conjugated flame-retardant composites were investigated. The flame-retardant properties of PLA-conjugated flame-retardant composites were characterized by the limiting oxygen index (LOI) and the vertical burning test (UL94). The results showed that the PLA-conjugated flame-retardant composites achieved a V-0 rating (UL-94, 3.2 mm) when the conjugated flame retardant was added at 5 wt%, and increase in LOI value from 22.5% to 31.4% relative to composites without added conjugated flame retardant. The flame-retardant mechanism of PLA-conjugated flame-retardant composites were further studied by TG-FTIR, the results showed that the P-PPD-Ph promoted the PLA-conjugated flame-retardant composites to decompose and also released fragments with quenching and dilution, which suggests that P-PPD-Ph for PLA-conjugated flame-retardant composites mainly play a role of the gas-phase flame retardant.

Metal Organic Framework@Polysilsesequioxane Core/Shell-Structured Nanoplatform for Drug Delivery.

Modern pharmaceutics requires novel drug loading platforms with high drug loading capacity, controlled release, high stability, and good biocompacity. Metal-organic frameworks (MOFs) show promising applications in biomedicine owing to their extraordinarily high surface area, tunable pore size, and adjustable internal surface properties. However, MOFs have low stability due to weak coordinate bonding and limited biocompatibility, limiting their bioapplication. In this study, we fabricated MOFs/polysilsesquioxane (PSQ) nanocomposites and utilized them as drug carriers. Amine-functionalized MOF (UiO-66-NH2) nanoparticles were synthesized and encapsulated with epoxy-functionalized polysilsesquioxane layer on the surface via a facile process. MOFs possessed high surface area and regular micropores, and PSQs offered stability, inertness, and functionality. The obtained UiO-66-NH2@EPSQ nanocomposites were utilized as carriers for ibuprofen, a drug with carboxylic groups on the surface, and demonstrated high drug loading capacity and well-controlled release property. The UiO-66-NH2@EPSQ nanocomposite exhibited low cytotoxicity to HeLa cells within a wide concentration range of 10-100 µg/mL, as estimated by the MTT method. The UiO-66-NH2@EPSQ drug release system could be a potential platform in the field of controlled drug delivery.

Crystallization behavior and optical properties of isotactic polypropylene filled with α-nucleating agents of multilayered distribution.

Isotactic polypropylene (iPP)-based multilayered composites containing alternating layers of pure iPP and α-nucleating agents (α-NAs)-filled iPP (αPP) were fabricated through layer-multiplying co-extrusion technology. With the manipulation of layer number, a tunable multilayered distribution of α-NAs was achieved and its effect on the crystallization behavior and optical properties of iPP was investigated. When the thickness of an individual iPP layer, which is equal to the distance between adjacent αPP layers, was large, the crystallization process of iPP was governed by homogeneous nucleation, although the crystallization of areas near the layer interfaces was induced by α-NAs. As a result, most iPP formed big spherulites thus a poor clarity. By decreasing the layer thickness via multiplying the layer number, the nucleation of iPP was gradually transformed from a homogeneous mode to a heterogeneous mode because of the more and more strong influence of αPP layers on the crystallization process of adjacent iPP layers. Consequently, iPP exhibited similar crystallization behavior compared with αPP. The polarized optical microscopy results further demonstrated that the size of spherulites in iPP was significantly reduced with the increase of layer number, which contributed to the enhancement of transmittance and decline of haze. Accordingly, this work developed a novel approach to tailor the crystallization behavior and optical properties of iPP.