Silica Microparticles Supported Gold and Copper Ferrite Nanoparticles: A Magnetically Recyclable Bimetallic Catalyst for Sonogashira Reaction

Novel silica supported gold and copper ferrite nanoparticles (NPs) have been synthesized, characterized and used as a separable dual catalyst in Sonogashira type reaction. These Au.CuFe2O4@Silica NPs show a high efficiency as catalyst in the alkynylation not only of aryl iodides but also aryl bromides. By using only 0.5 mol% loading and t-BuOK as base in N,N-dimethylacetamide as solvent, aryl iodides react at 115 ºC in 1 d, whereas for aryl bromides the cross-coupling takes place at 130 ºC in 2 d. The catalyst can be successfully recycled using an external magnet for four consecutive runs.

Organic distributed feedback laser to monitor solvent extraction upon thermal annealing in solution-processed polymer films

Solution-processed polymer films are used in multiple technological applications. The presence of residual solvent in the film, as a consequence of the preparation method, affects the material properties, so films are typically subjected to post-deposition thermal annealing treatments aiming at its elimination. Monitoring the amount of solvent eliminated as a function of the annealing parameters is important to design a proper treatment to ensure complete solvent elimination, crucial to obtain reproducible and stable material properties and therefore, device performance. Here we demonstrate, for the first time to our knowledge, the use of an organic distributed feedback (DFB) laser to monitor with high precision the amount of solvent extracted from a spin-coated polymer film as a function of the thermal annealing time. The polymer film of interest, polystyrene in the present work, is doped with a small amount of a laser dye as to constitute the active layer of the laser device and deposited over a reusable DFB resonator. It is shown that solvent elimination translates into shifts in the DFB laser wavelength, as a consequence of changes in film thickness and refractive index. The proposed method is expected to be applicable to other types of annealing treatments, polymer-solvent combinations or film deposition methods, thus constituting a valuable tool to accurately control the quality and reproducibility of solution-processed polymer thin films.

Performance Assessment of a Polymer Electrolyte Membrane Electrochemical Reactor under Alkaline Conditions – A Case Study with the Electrooxidation of Alcohols

A novel polymer electrolyte membrane electrochemical reactor (PEMER) configuration has been employed for the direct electrooxidation of propargyl alcohol (PGA), a model primary alcohol, towards its carboxylic acid derivatives in alkaline medium. The PEMER configuration comprised of an anode and cathode based on nanoparticulate Ni and Pt electrocatalysts, respectively, supported on carbonaceous substrates. The electrooxidation of PGA was performed in 1.0 M NaOH, where a cathode based on a gas diffusion electrode was manufactured for the reduction of oxygen in alkaline conditions. The performance of a novel alkaline anion-exchange membrane based on Chitosan (CS) and Poly(vinyl) alcohol (PVA) in a 50:50 composition ratio doped with a 5 wt.% of poly (4-vinylpyridine) organic ionomer cross-linked, methyl chloride quaternary salt resin (4VP) was assessed as solid polymer electrolyte. The influence of 4VP anionic ionomer loading of 7, 12 and 20 wt.% incorporated into the electrocatalytic layers was examined by SEM and cyclic voltammetry (CV) upon the optimisation of the electroactive area, the mechanical stability and cohesion of the catalytic ink onto the carbonaceous substrate for both electrodes. The performance of the 4VP/CS:PVA membrane was compared with the commercial alkaline anion-exchange membrane FAA −a membrane generally used in direct alcohol alkaline fuel cells- in terms of polarisation plots in alkaline conditions. Furthermore, preparative electrolyses of the electrooxidation of PGA was performed under alkaline conditions of 1 M NaOH at constant current density of 20 mA cm−2 using a PEMER configuration to provide proof of the principle of the feasibility of the electrooxidation of other alcohols in alkaline media. PGA conversion to Z isomers of 3-(2-propynoxy)-2-propenoic acid (Z-PPA) was circa 0.77, with average current efficiency of 0.32. Alkaline stability of the membranes within the PEMER configuration was finally evaluated after the electrooxidation of PGA.

Polymer Fluid Dynamics: Continuum and Molecular Appoaches

To solve problems in polymer fluid dynamics, one needs the equation of continuity, motion, and energy. The last two equations contain the stress tensor and the heat-flux vector for the material. There are two ways to formulate the stress tensor: (1) one can write a continuum expression for the stress tensor in terms of kinematic tensors, or (2) one can select a molecular model that represents the polymer molecule, and then develop an expression for the stress tensor from kinetic theory. The advantage of the kinetic theory approach is that one gets information about the relation between the molecular structure of the polymers and the rheological properties. In this review, we restrict the discussion primarily to the simplest stress tensor expressions or “constitutive equations” containing from two to four adjustable parameters, although we do indicate how these formulations may be extended to give more complicated expressions. We also explore how these simplest expressions are recovered as special cases of a more general framework, the Oldroyd 8-constant model. The virtue of studying the simplest models is that we can discover some general notions as to which types of empiricisms or which types of molecular models seem to be worth investigating further. We also explore equivalences between continuum and molecular approaches. We restrict the discussion to several types of simple flows, such as shearing flows and extensional flows. These are the flows that are of greatest importance in industrial operations. Furthermore, if these simple flows cannot be well described by continuum or molecular models, then it is not necessary to lavish time and energy to apply them to more complex flow problems.

Grafting of functional brushes on the surface of 5-Fluorouracil molecularly imprinted polymer particles through RAFT polymerization

The grafting of functional brushes on the surface of molecularly imprinted polymer (MIP). particles hás been explored in the last few years to synthesize materiais combining high molecular recognition capabilities and stimulation triggered by changes in the surrounding environment [1, 2]. In the present work, MIP particles for 5-fluorouracil (a drug used in câncer treatment) were produced by precipitation polymerization in acetonitrile, using either MAA or HEMA as imprinting fünctional monomers, and m the presence of different kinds of RAFT agents. In a second step, taking advantage of the RAFT groups present in the surface of the particles, different kinds of fiinctional polymer brushes were grafted on the MIPs considering a "grafting from" process in the presence of a RAFT agent.

The Problem Sensitization Robotic Complex Drilling and Milling of Sandwich Shells of Polymer Composites

In clause is given robotic a complex for drilling and milling sandwich shells from polymeric composites. The machining of polymeric composite materials has technological problems. At drilling sandwich shells there is a probability of destruction of a drill from hit of the tool in a partition. The system sensibilization robotic complex for increase of reliability of work of the cutting tool of the small size is offered.

Design of continuously reinforced concrete pavements using glass fiber reinforced polymer rebars /

"October 2005."

Piezoelectric polymer transducers for dynamic pressure measurements. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Colloid and polymer science. Kolloid-Zeitschrift & Zeitschrift für Polymere

Mode of access: Internet.

A study of the mechanism of radiation-induced gelation in monomer-polymer mixtures : report for the period May 1, 1961 - October 31, 1962 /

"October 31, 1962."

A study of the mechanism of radiation-induced gelation in monomer-polymer mixtures : report for the period May 1, 1961 - October 31, 1963 /

"November 31, 1963."

Concrete-polymer materials : fourth topical report /

Mode of access: Internet.

Fiberglass reinforced polymer composite bridge deck construction in Illinois /

"Report no. FHWA/IL/PRR-145"--Technical rept. documentation p.

Principles of high-polymer theory and practice; fibers, plastics, rubbers, coatings, adhesives,

Includes bibliographies.