Hydrotalcite-like anionic clays in catalytic organic reactions

Hydrotalcite-like anionic clays (HTs; or layered double hydroxides, LDHs) can be used as precursors to mixed oxides, but their catalytic potential reaches much further. This review demonstrates that HTs can be successfully applied in a broad spectrum of organic reactions, with advantages such as improved activity, selectivity, metal dispersion, less waste production, and an improved recuperation of immobilized catalysts. HTs can be used in the as-synthesized form or after different pretreatments. The HT as such is a solid base or, depending on the elemental composition of its octahedral layers, may have redox properties. Specific metals can be incorporated either as a cation in the octahedral layer or as an anion via exchange. The anion-exchange strategy is especially successful in the context of heterogenizing homogeneous catalysts. A particular advantage for base catalysis is that the number and strength of the basic sites can be tuned precisely to a specific reaction. HTs are excellent materials to design bifunctional redox-base catalysts or to control the acid-base properties around a heterogenized metal complex. Potential applications of HTs range from the production of large-scale basic chemicals to the synthesis of small-scale specialty chemicals.     

Effects of 1,4-Benzoxazin-3-One Derivatives from Maize on Survival and Fecundity of Metopolophium dirhodum (Walker) on Artificial Diet

Effects of 2--D-glucopyranosyloxy-4-hydroxy-7-methoxy-1,4benzoxazin-3-one (DIMBOA-Glc) and DIMBOA-Glc N-O-methylated (HDMBOA-Glc), two compounds present in high concentration in maize, were tested on the aphid Metopolophium dirhodum reared on artificial diet. HDMBOA-Glc and DIMBOA-Glc decrease survival of adults with an LD₅₀ of 1 mM and 5.6 mM, respectively, after 72 hr of feeding. These compounds also decrease the fecundity of the aphids at concentrations of 2 mM and 1 mM, respectively. At concentrations of 2 mM HDMBOA-Glc and 8 mM DIMBOA-Glc in the diet, the average lifetime fecundity of 10 females is near zero. Offspring mortality on diet with 2 mM DIMBOA-Glc is significantly higher than with the control diet. In contrast, HDMBOA-Glc has no effect on the survival of offspring. The possibility that these compounds protect Poaceae against aphids is discussed.     

Effect of hydroxy-aluminium species on the sorption and interlayering of albumin onto montmorillonite

Proteins interact with soluble OH–Al species or Al precipitation products forming organo-mineral complexes with different chemical and physico-chemical properties. We studied the effect of pH, cation saturating the clays, presence of OH–Al species and order of component (OH–Al species, albumin and montmorillonite) addition on the amounts of proteinic molecules adsorbed on montmorillonite and the possible interlayering of OH–Al–protein complexes. Albumin molecules were very well intercalated into the interlayers of Na-montmorillonites, but very poor or no intercalation was observed for Mg-saturated montmorillonite and for an Al(OH)_x-montmorillonite (chlorite-like) complex.We have found that the amount of albumin sorbed on the external and interlamellar spaces of montmorillonite in the presence of OH–Al species was influenced by the sequence of addition of albumin (Alb), OH–Al species (Al) and montmorillonite (Mt). Complexes were prepared by mixing: (i) Al+Mt before Alb; (ii) Al+Alb before Mt; and (iii) Alb+Mt before Al. When albumin was added to montmorillonite before OH–Al species (Alb+Mt before Al complexes) proteinic molecules were able to penetrate more easily into the interlayers of montmorillonite. On the contrary, when OH–Al species were initially added to the clay (Al+Mt before Alb complexes), they were previously interlayered and consequently prevented the intercalation of the proteinic molecules. Finally, when OH–Al species and proteins were added to the clay as a mixture (Al+Alb before Mt complexes), large OH–Al–protein polymers formed, which were only partially intercalated into the interlamellar spaces of the clay. In all the complexes, the amounts of proteinic molecules sorbed usually increased by increasing the pH.     

Studies on compatibility of biodegradable starch/polyvinyl alcohol blends

Compatibility of starch/polyvinyl alcohol (PVA) blends, prepared by solution cast method, is dependent on the blend composition. Crystallinity of the blend, as measured by X‐ray diffraction (XRD) and differential scanning calorimeter (DSC), decreases with increase in starch content. Thermogravimetric analysis (TGA) shows that the broadness in the peak width at the degradation region increases with increase in starch content in the starch/PVA blend. Dynamic mechanical thermal analysis (DMTA) reveal that the broadness of the relaxation peaks is due to the partial compatibility of the glycerol plasticized starch/PVA blends. The tensile property decreases with increase in starch content and the 30/70 starch/PVA blend shows maximum ductility in respect to both the percentage of elongation and energy at break. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Synthesis,characterization, and properties of new siloxane grafted copolyimides

Three new siloxane containing grafted copolyimides have been prepared by one‐pot solution imidization technique. The polymers are made by the reaction of 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) with commercially available diamine 4,4′‐oxydianiline (ODA) with variation of silicon containing diamine, namely 3,5‐diaminobenzoate terminated polydimethylsiloxane (DBPDMS), as a comonomer to 10, 20, and 30 wt %. The films of the polymers were prepared by casting the polymer solution in dichloromethane. The polymers have been well‐characterized by GPC, IR, and NMR techniques. Thermal stabilities and decomposition behavior of the copolyimides were studied by DSC and TGA. The water contact angle values of the films indicate hydrophobic nature of the polymers. Thermal, flame retardant, mechanical, and surface properties of these polymers have been compared with the homopolyimide and with polyimides where polysiloxane is incorporated in the main chain. DSC revealed melting of the grafted siloxane chain at sub‐ambient temperature and a glass transition corresponding to the main polymer chain above 200°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel copolymer for SiO2 nanoparticles dispersion

High performance polymers exhibiting multifunctional characteristics can be achieved by the introduction of inorganic nanoparticles like SiO₂ into the functional polymers. In the present work a copolymer epoxy poly(dimethylacrylamide) was synthesized to disperse the SiO₂ nanoparticles. The aim of the work is to develop a new method/process/material for the dispersion of nanoparticles and evaluating the performance of these composites. FT‐IR studies of the polymer adsorbed SiO₂ nanoparticles confirmed that the polymer molecules chain was anchored on the surface of the SiO₂ nanoparticles. The improved interfacial interaction between the particles and polymer enhanced the thermal properties of the composites. The results also show the newly synthesized polymer disperse the nanoparticles well as evidenced by SEM analysis, the uniformly dispersed SiO₂ nanoparticles in the polymer matrix and the particles almost remained in their original shape and size even after incorporation in to the polymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of phenol functionalization of carbon nanotubes on properties of natural rubber nanocomposites

This paper reports the results of studies on the effect of phenol functionalization of carbon nanotubes (CNTs) on the mechanical and dynamic mechanical properties of natural rubber (NR) composites. Fourier transform infrared spectrometry (FTIR) indicates characteristic peaks for ether and aromatic rings in the case of phenol functionalized CNT. Although differential scanning calorimetric (DSC) studies show no changes in the glass‐rubber transition temperature (T_g) of NR in the nanocomposites due to surface modification of CNT, dynamic mechanical studies show marginal shifting of T_g to higher temperature, the effect being pronounced in the case of functionalized CNT. Stress‐strain plots suggest an optimum loading of 5 phr CNT in NR formulations and the phenolic functionalization of CNT does not affect significantly the stress‐strain properties of the NR nanocomposites. The storage moduli register an increase in the presence of CNT and this increase is greater in the case of functionalized CNT. Loss tangent showed a decrease in the presence of CNT, and the effect is more pronounced in the case of phenol functionalized CNT. Transmission electron microscopy (TEM) reveals that phenol functionalization causes improvement in dispersion of CNT in NR matrix. This is corroborated by the increase in electrical resistivity in the case of phenol functionalized CNT/NR composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Aromatic Linkers Unleash the Antiproliferative Potential of 3-Chloropiperidines Against Pancreatic Cancer Cells

In this study, we describe the synthesis and biological evaluation of a set of bis-3-chloropiperidines (B−CePs) containing rigid aromatic linker structures. A modification of the synthetic strategy also enabled the synthesis of a pilot tris-3-chloropiperidine (Tri-CeP) bearing three reactive meta-chloropiperidine moieties on the aromatic scaffold. A structure–reactivity relationship analysis of B−CePs suggests that the arrangement of the reactive units affects the DNA alkylating activity, while also revealing correlations between the electron density of the aromatic system and the reactivity with biologically relevant nucleophiles, both on isolated DNA and in cancer cells. Interestingly, all aromatic 3-chloropiperidines exhibited a marked cytotoxicity and tropism for 2D and 3D cultures of pancreatic cancer cells. Therefore, the new aromatic 3-chloropiperidines appear to be promising contenders for further development of mustard-based anticancer agents aimed at pancreatic cancers.     

Relative expression and regulation by short-term fasting of lysophosphatidic acid receptors and autotaxin in white and brown adipose tissue depots

Lysophosphatidic acid (lysoPtdOH) levels have previously been reported to decrease in rodents with short-term fasting. We investigated whether a 16 h fast would change expression of autotaxin, the predominant phospholipase D responsible for adipose-derived lysoPtdOH synthesis, or any of the lysophosphatidic acid receptors (1–6) in four white adipose tissue (WAT) depots and interscapular brown adipose tissue (BAT) in male C57Bl/6J mice fed ad libitum, or fasted for 16 h. Aside from small inductions of Lpar1 in epididymal WAT and Lpar2 in epididymal and inguinal WAT, no significant changes were observed in expression of the Lpar family members, or autotaxin in perirenal, retroperitoneal, epididymal, or inguinal WAT or BAT with fasting. Comparison of the relative expression of Lpar1-6 in various depots showed that Lpar6 was the predominant Lpar in both WAT and BAT, and suggests that further work on the adipose-specific role of Lpar6 is warranted.     

Additional high-energy milling to enhance the performance of porcelain stoneware manufacturing

Porcelain stoneware tile is the best class of ceramic tiles regarding technical performance. Low porosity and high glass content are some of its highlighted characteristics. The manufacturing cost is highly dependent on the feldspar content and the processing flow rate. Certain technical bottlenecks in the manufacturing steps, such as milling, forming, and firing, are intrinsically associated with limitations in the processing properties, such as the dry strength, bulk density, and pyroplastic deformation. In this work, improvements in these properties were achieved using high-energy milling (HEM) after conventional milling (CM). This study was carried out on a pilot industrial scale in the milling stage. Six experimental runs were evaluated. Slurries were spray-dried. The powders were humidified with 6.5% moisture. Specimens were conformed under a specific pressure of 45 MPa. The firing was performed using temperature ranging from 1150 to 1230°C. The use of HEM, in comparison to traditional milling for the similar particle-size distributions, has increased the dry density, +0.2 g.cm⁻³, dry bending strength, +1.0 MPa, and decreased the pyroplastic deformation index, −1.10⁻⁵ cm⁻¹. These results allow an estimated thickness reduction of 10%.