Palladium metal nanoparticles on organically modified thin hybrid films

Hybrid thin films containing palladium nanoparticles in different concentrations (0.5% and 1%) with and without nanoparticle stabiliser agent [mercaptopropyl trimethoxysilane, MPTMS] were prepared using a sol–gel process. Pd nanoparticles were found to be highly dispersed on the thin films with particles ranging from 7 to 10 nm. The catalytic properties of the thin films supported Pd nanoparticles were investigated in the Heck reaction of iodobenzene and methyl acrylate. Films containing Pd MNP (with and without MPTMS) gave quantitative conversion and complete selectivity to the targeted product (methyl cinnamate) in a short time of reaction (<15 min) under microwave irradiation. While Pd containing films without MPTMS were highly active and reusable after 3 runs, MPTMS containing films were found to be inactive after the first use. Such phenomenon was correlated to the steric hindrance round the Pd MNP due to the adsorption of species on the surface that render the catalysts inactive.     

Effects of killing conditions of vanilla (Vanilla planifolia,Andrews) pods during the curing process on aroma composition of pod ethanol extract

The effects on the aroma compositions of ethanol extracts obtained by traditional and enzyme‐assisted methods from seven killing conditions used in vanilla pod curing were studied. Two procedures of vanilla pod killing consisted of either freezing pods at ?10 °C for 24 h or immersing pods in 80 °C water for 10 s each of three times with 30 s intervals resulted in the highest vanillin values in terms percentage of dry weight of the bean (2.84 and 2.96), 4‐hydroxybenzaldehyde (0.18 and 0.20), vanillyl alcohol (0.56 and 0.57) and vanillic acid (0.18 and 0.19 respectively) when traditional vanilla ethanol extraction was used. When this extract was aged for 3 months it showed improvement in flavour compounds. Enzyme‐assisted vanilla ethanol extraction showed a higher content of flavour compounds than traditional extract, for example vanillin 4.38% and 2.96% respectively. Only vanillic acid levels were improved after ageing of the enzyme‐assisted extracts.     

Smart polymer recycling: Synthesis of novel rigid polyurethanes using phosphorus‐containing oligomers formed by controlled degradation of microporous polyurethane elastomer

This article describes a new approach for the recycling of microporous polyurethane elastomers by Tris(1‐methyl‐2‐chloroethyl) phosphate‐induced degradation. The phosphorus‐containing degradation products formed are transformed into reactive intermediates by reaction with propylene oxide and are used for the preparation of rigid polyurethane foams. These new phosphorus‐containing materials have higher density and better mechanical properties compared to the standard rigid polyurethane foams. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Gamma irradiated orange peel for Cr(VI) bioreduction

This work presents the γ irradiation (600–3500 kGy) and acid hydrolysis onto orange peel for hexavalent chromium removal. SEM, AFM, TGA-DSC, FTIR, and UV-Vis showed that γ rays enhance degradation and cleavage of orange peel cellulose polymeric chains, increasing the presence of reducing sugars after acid hydrolysis (0.1552 g/g biomass, 3500 kGy). Bioreduction kinetics of Cr(VI) using both solid and solubilized liquid fractions of γ irradiated biomass showed a direct correlation between the applied dose and Cr(VI) removal, reaching 100% of Cr(VI) reduction at pH 2 and 3500 kGy. Cr(VI) reduction is explained as a function of hydrolyzed reducing sugar oxidation.     

Effect of cinnamate comonomers on the dental formulation properties

This study reports the synthesis and characterization of two urethane dimethacrylates containing poly(ethylene oxide) or poly(propylene oxide) segment and cinnamate pendant moieties to be formulated in dental resin composites. ¹H NMR, ¹³C NMR, and Fourier transform infrared spectroscopies, gel permeation chromatography, electrospray ionization‐mass spectroscopy, and thermogravimetric measurements confirmed their structure, whereas the photopolymerization evolution of oligodimethacrylates relating to a low–molecular‐weight dicinnamate methacrylate under ultraviolet irradiation was investigated by photo‐differential scanning calorimeter, monitoring the degree of conversion (DC) and polymerization rate. The photopolymerization results reveal that the investigated derivatives display a good photoreactivity (DC: ～ 70%) during the formation of crosslinked polymers, the DC depending especially on the sample viscosity. The polymerization shrinkage for several mixtures including the urethane oligocinnamates (20 wt %) and diglycidyl methacrylate of bisphenol A/triethyleneglycol dimethacrylate system in the absence of filler was determined, the obtained values being in the range of 6.1–8.2 vol %. For few cured specimens incorporating quartz filler (75 wt %), water sorption/solubility, contact angle, and mechanical parameters were measured to establish if such monomers could be of interest in dentistry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013