Reactive Polymers最新文献

Pd- and Rh-containing polymeric catalysts were studied in hydrogenation of acetylene alcohols and unsaturated ketones which are intermediates in production of vitamins and fragrant substances. The influence on catalytic properties of supporting the prepared polymers on Al₂O₃ was investigated. The increase of stability and selectivity of supported Pd-containing polymer in the hydrogenation of long-chain acetylene alcohols was shown to occur. The supporting of Rh-containing polymer on Al₂O₃ also resulted in an increase of thermal stability of catalyst and increase of working time as compared with unsupported or traditional catalysts.

The thermochromism of Ni(II) complexes of cresolphthalein dye was studied in pyridine-containing acrylamide copolymers with N-vinyl-pyrrolidone (VP) or N-isopropylacrylamide (IPA). Pendant pyridine moieties in the copolymers affect the sensitivity of color development and stability of color species. A large temperature dependence was obtained in the copolymer 2-acrylamido-N-3-pyridylpropanoamide pyridine with VP and the developed color was stable in copolymer of N-3-pyridylacrylamide with IPA.

Poly(vinyl acetate) (PVAc) has been transformed into a polymer having the structure of PVAcSOMe via hydrolysis, 3-methylthiopropionylation and oxidation. The obtained PVAcSOMe copolymers have been shown to have the property of accelerating the penetration of triphenylphosphite through parchment paper.

Studies have been conducted on the sorption of several heavy metal ions Cu(II), Ni(II), Zn(II), Cd(II) and Al(III) from aqueous solutions on the new chelating exchangers of sporopollenin (Lycopodium clavatum) as a function of pH at several temperatures between 20 and 50°C. The novel metal-ligand exchange resins possessing oxime and carboxylic acid side arm functionality were prepared through the reaction of diaminosporopollenin with dichloroantiglyoxime and bromoacetic acid. The sorption of all metals increased considerably in the range of pH 6–10 and was observed in sequence as: Cu ≥ Ni > Zn > Cd > Al for carboxylated-diaminoethyl-sporopollenin (DAEC) and Ni ≥ Cu > Zn > Cd > Al for bis-diaminoethyl-glyoxime-sporopollenin (bDAEG). The level of pH of the aqueous medium had a large influence on the sorption capacity, and the uptake of metals, except Al(III), was found to be 90% or more. The metal-form resins afforded complete recovery of the sorbed species by acid stripping. Both resins also showed high stability towards concentrated acids and bases and retained their high capacity for heavy metals.

A newly available, macroporous anion-exchange resin Reillex™ HPQ, which has about 70% of the pyridine rings quaternized by the addition of methyl groups, has been used in the chloride form for the sorption of sulfide from alkaline aqueous medium. Comparative data on sulfide sorption capacity and kinetics in alkaline media are presented for this new resin and a common anion exchange resin Dowex-1-X8, both used in chloride form. The sulfide sorption capacities of HPQ(Cl⁻¹) and Dowex-1(Cl⁻¹), activated by treatment with mixed NaCl/HCl solution, are found to be 4.8 and 2.5 mmol S/g (dry), respectively, compared to the respective total exchange capacities of 4.6 and 5.6 mEq/g (dry), indicating that sulfide is predominantly sorbed as univalent HS⁻ on HPQ(Cl⁻) and as bivalent S²⁻ on Dowex-1(Cl⁻) this is attributed to the occurrence of nearly 30% of the pyridine sites in HPQ(Cl⁻) in protonated form, contributing to lower pH inside the resin phase as compared to external medium. The chloride/sulfide exchange kinetics, in conditions of particle diffusion control and infinite solution volume, are predicted with good approximation by the Nernst-Planck model. Both the chloride and sulfide counterions taking part in the exchange process diffuse very slowly in the resin, the diffusion coefficients being in the order of 10⁻¹⁰ cm²/s, though chloride ions have relatively higher diffusivity than the sulfide ions.

Selective hydrogenation of anisol to cyclohexyl methyl ether in 100% yield has been achieved by a new natural polymer catalyst, silica-supported carboxymethyl cellulose-platinum complex (SiO₂CMCPt) at 30°C and 1 atm mild reaction conditions. The $\text{COO}\text{Pt}$ ratio, temperature and solvent had great influence on the reaction. The catalyst was stable during the reaction, its catalytic properties were little changed after being reused 4 times.

Polymeric azosulfonates lose their water solubility when exposed to UV light due to decomposition of the azo function. This effect can be used in water-based photoprinting processes. Water-soluble copolymers of azosulfonate containing repeat units and methyl methacrylate have been alternatively synthesized by a polymer-analogous reaction [1,2] and by direct copolymerization [3]. Both polymer types have been evaluated for application as photoresins in offset printing processes. The polymer made by copolymerization is superior and shows excellent results for photosensitivity, resolution, film-forming properties, and development in water, as well as for thermal and moisture storage stability.

Fiber chromatography is prominent among the novel systems being developed for downstream processing. In this research, a polymer based anion-exchange support with fiber geometry has been developed. The fiber support has an asymmetric structure, with a dense skin and a porous substructure. Equilibrium adsorption capacities of this support for bovine serum albumin and β-lactoglobulin were measured. Isotherms were obtained at different pH and salt concentrations, and were found to be Langmuirian. It was also found that ion-exchange is the dominant adsorption mechanism, and, due to a large internal surface area, the support has a high adsorption capacity. The fiber support was packed in a bed, and tested for its applicability in the isolation of proteins from dilute solutions. The fiber column is shown to have a significantly lower pressure drop than columns packed with commercial, spherical supports. The frontal throughout for this column was evaluated at different conditions. The throughput was found to increase with flow rate and protein concentration, but the yield dropped with an increase in flow rate. However, the throughput and yield were high when a high concentration of protein was loaded at a low flow rate and washed at a very high flow rate.

In this paper, we show that the l-enantiospecific hydrolysis of d,l-α-aminonitriles into l-α-amino acids is catalyzed by an amidase (pronase) immobilized on poly(N-acryloylpiperidin-4-one). Actually, the support chemically participates in the catalytic action since the ketonic sites (piperidin-4-one) catalyze the d,l-α-aminonitrile hydration into d,l-α-aminoamide in a medium specifically buffered by borates or phosphates at pH 10–11. These conditions are compatible with the enzymatic activity of the pronase and allow the simultaneous transformation of the d,l-α-aminoamide formed in the resin into the corresponding l-α-amino acid.

The effects of various reaction parameters on the catalytic activity and stereoselectivity in the hydrogenation of the isomeric xylenes over a silica-supported polysilazane-platinum complex (SiNPt) have been studied. The ratio of cis and trans dimethylcyclohexane is a function of the structure of the substrate, temperature and catalyst concentration etc. cis-Dimethylcyclohexane is the more favored product for each of the three xylene isomers. The $\text{cis}\text{trans}$ ratio drops in the following order: o-xylene > m-xylene > p-xylene. The proportion of the cis isomer decreases with elevating temperature or decreasing substrate/catalyst mole ratio.