Methylenemalonic aldehydes and their use in organic synthesis (review)

The review is devoted to the use of methylenemalonic aldehydes in the synthesis of diverse heterocycles — pyrans, dihydropyrans, dihydrofurans, oxazoles, oaxadiazines, pyrazoles, and diazepines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1026, August, 1991.     

Hyperbranched polymers for molecular imaging: designing polymers for parahydrogen induced polarisation (PHIP)

The first hyperpolarisation of polymers using parahydrogen induced polarisation (PHIP) is reported by hydrogenation of terminal alkyne groups in a biocompatible hyperbranched polymer. Signal enhancements of 1500-fold could be obtained depending on the structure of the polymer, thus opening new potential avenues for polymeric molecular imaging.     

Proton-ionizable acyclic dibenzopolyethers and their polymers for use in selective lead(II) separation

Abstract

2,2′-[1,2-Ethanediylbis(oxy)]bisbenzoic acid (1), 2,2′-[oxybis(1,2-ethanediyloxy)]bisbenzoic acid (2), 1,2-[2′-(acetoxy)phenoxy] ethane (3), and 1,5-[2′-(acetoxy)phenoxy]-3-oxopentane (4) have been prepared for use in selective Pb(II) separation. The extraction of Pb(II) and Cu(II) from buffered aqueous solutions of varying pH into chloroform by 1–4 is examined in relation to their molecular structure. Compound 1 with an ethylene glycol spacer unit exhibits excellent extraction selectivity for Pb(II) over Cu(II). Lengthening the spacer group to a diethylene glycol unit diminishes the extraction efficiency and selectivity. For 3 and 4, extraction was inefficient due to low lipophilicity and solubility of the ligands in chloroform. Condensation polymerization of compounds 3 and 4 with formaldehyde in formic acid provides stable chelating resins 5 and 6 which contain both ion-exchange and polyether binding sites for metal complexation. Resin 5 with an ethylene glycol spacer group is found to be an effective chelating resin for Pb(II) separation. The sorption mechanism and selectivity are studied and compared with the commercially available iminodiacetic acid resin CR-10.     

Synthesis and properties of iron oxide coated carbon nanotubes hybrid materials and their use in epoxy coatings

Multi‐walled carbon nanotubes (MWCNTs) were acidified with nitration mixture, and the Fe₂O₃‐MWCNTs (iron oxide coated multi‐walled carbon nanotubes) hybrid material via sol‐gel method then verified the results through scanning electron microscope, X‐ray diffraction, and thermal gravimetric analysis. We modified the hybrid material with silane coupling agent (KH560), Fe₂O₃‐MWCNTs/epoxy, MWCNTs/epoxy composites coating, and the pure epoxy coatings were respectively prepared. The properties of the composite coatings were tested through the electrochemical workstation (electrochemical impedance spectroscopy), shock experiments, and thermal gravimetric analysis. Finally, we used scanning electron microscope to observe the surface conditions of the coatings. The results show that Fe₂O₃‐MWCNTs have good dispersion in the epoxy resin, and the Fe₂O₃‐MWCNTs/epoxy composite coatings have enhanced mechanical properties and corrosion resistance. Copyright © 2015 John Wiley & Sons, Ltd.     

Phosphorylcholine-based polymers and their use in the prevention of biofouling

This article provides an overview of work carried out on the synthesis and non-fouling properties of phosphorylcholine (PC)-containing polymers. The concept of biomimicry is outlined and the major classes of synthetic PC-based materials described. Studies on the interaction of these materials with various proteins are collated and the mechanism for their protein-resistant nature is discussed. Similarly, cellular interactions are also reviewed, with ex-vivo and in-vivo clinical data provided to demonstrate the usefulness of these materials for improving the properties of medical devices.     

Vinyl chloride polymers and their use in polymer blends

A short introduction to polymer-polymer miscibility and to the prediction of the miscibility of polymers is given. The four main types of polymer-modified poly(vinyl chloride) (plastification, impact modification, processing aids and heat deflection temperature modification) are explained by examples. The thermal stability of poly(vinyl chloride) in such blends is discussed; the effectivity of tin-stabilizers may be higher in such blends than in pure poly(vinyl chloride).     

A review on amperometric immunoassays for tumor markers based on the use of hybrid materials consisting of conducting polymers and noble metal nanomaterials

Conducting polymers possess good conductivity, can be easily modified, have a particular redox activity. Noble metal nanomaterials, in turn, possess high conductivity, catalytic properties and large surface-to-volume ratios. Synergistic materials consisting of both conducting polymer and metal nanomaterial therefore are most useful materials for use in electrochemical immunosensors with improved sensitivity and specificity. This review (with 75 references) gives an overview on advances in conducting polymer based noble metal nanomaterial hybrids for amperometric immunoassay of the 13 most common tumor markers. The review is divided into the following sections: (1) Polyaniline based noble metal nanomaterial hybrids; (2) Polyaniline derivative-based noble metal nanomaterial hybrids; (3) Polypyrrole-based noble metal nanomaterial hybrids. A final section covers future perspectives regarding challenges on the design of electrochemical immunoassays.

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Graphical abstract Advances on conducting polymer and noble metal nanomaterial hybrids for amperometric immunoassay of tumor marker are reviewed. Future perspectives regarding challenges on the construction of electrochemical immunosensing interface for tumor marker are discussed.

     

Ionic liquids and their use for the dissolution of natural polymers

The experimental and calculated data on the structure and properties of ionic liquids are presented. The prospects for their use as the solvents for natural polymers are considered.     

Surface active azogroup-containing polymers and their use in emulsion polymerization

Polymeric azoinitiators have been obtained by the acidcatalyzed polyreaction of azobisisobutyronitrile (AIBN) with tetraethylene glycol (TEG) and 1.6-hexanediol resp. The kinetics of decomposition of these polyazoesters were investigated by differential scanning calorimetry (DSC) resulting in an activation energy of E_a=124.5 KJ/mol and a frequency factor of A= 3.6 · 10¹⁴ sec^–1.The polyazoesters were used to initiate radical polymerization of acrylamide limiting the decomposition of the initiator to 37%. The resulting polyacrylamides containing azogroups had molecular weights between 50 000 and 250 000 g/mol. They are surface active polymers having a critical micell concentration of 0.1 to 0.3 g./l. By use of these polyacrylamides as an emulsifying initiator system stable emulsions of polymers were obtained without additional use of a tenside. Polymethacrylic acid containing azogroups can be used as well as an emulsifying initiator.The latex particles are stabilized by a solvated shell of a polymer. Thus it is possible to obtain stable emulsions in organic solvents by use of an azogroup-containing prepolymer which is soluble in that solvent. An emulsion of polyacrylamide in methanol ohtained by use of an azogroup-containing polyvinylacetate is an example.Dedicated to Professor F. H. Müller.Thanks are due to Dr. R. Menhold, Bayer AG, Leverkusen for performing the electronmicroscopic investigations. Financial support by Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie is gratefully acknowledged.     

The use of polymers in Li‐S batteries: A review

Recent developments in the use of polymeric materials as device components in lithium sulfur (Li‐S) batteries are reviewed. Li‐S batteries have generated tremendous interest as a next generation battery exhibiting charge capacities and energy densities that greatly exceed Li‐ion battery technologies. In this Highlight, the first comprehensive review focusing on the use of polymeric materials throughout these devices is provided. The key role polymers play in Li‐S technology is presented and organized in terms of the basic components that comprise a Li‐S battery: the cathode, separator, electrolyte, and anode. After a straightforward introduction to the construction of a conventional Li‐S device and the mechanisms at work during cell operation, the use of polymers as binders, protective coatings, separators, electrolytes, and electroactive materials in Li‐S batteries will be reviewed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1635–1668     

New aromatic oligoesters and their use in the synthesis of heat-resistant polyurethane coatings

For manufacturing new varnish polyurethane coatings with high hardness and elasticity at maintaining adhesion and strength properties oligoester diols were synthesized based on hydroxyethylated diphenylpropane derivatives and aromatic dicarboxylic acids.     

A Hyperbranched Poly(ethyleneimine) Grown on Surfaces

Aminosilylated substrate was treated with aziridines in order to prepare hyperbranched polymers on solid supports such as silicon wafer and fused silica. It is observed that the primary amine on the substrate is good enough to initiate the ring-opening polymerization of aziridine. Measuring the thickness of the film and the absolute density of the primary amine functionality shows that a very highly branched poly(ethyleneimine) is formed upon the reaction. The surface density of the primary amine functional group (-NH(2)) on the very top surface increased dramatically (from 3.5 amines/nm(2) to 66 amines/nm(2)). A protected aziridine, benzyl 1-aziridinecarboxylate, was employed for the stepwise growth of the film. Two step-processes, chain growth and deprotection, were successful in growing the molecular layer, and a linear chain was formed without branching. Copyright 2000 Academic Press.     

Perfluorinated ion exchange polymers and their use in research and industry

Tetrafluoroethylene is copolymerized with a perfluorovinyl ether, containing a functional end group (-SO₂F or -CO₂CH₃) to yield a melt fabricable precursor polymer. After fabrication into the desired shape, the polymer is treated with a solution of potassium hydroxide to convert the functional group to an ion exchange site. The fundamental incompatibility of the ionic group with the perfluorinated polymer backbone results in a unique morphology, particularly in the presence of water or polar organic solvents. This has been the subject of extensive investigations by various research institutions. The most important industrial use for these polymers is in the electrolysis of sodium chloride solutions. Initially introduced in order to eliminate the environmental problems of the amalgam process, their performance has now improved to the point where they offer substantial savings, particularly in terms of energy costs, over the two older processes. An emerging, potentially very important use for perfluorinated ion exchange polymers is as an ionic conductor in fuel cells. Recent advances in this area will be discussed.     

Benzazetines and their derivatives (review)

Published information on methods for the production of benzazetines and their dehydro derivatives (benzazetes) and their chemical transformations is reviewed and analyzed. It was noted that benzazetines with an unsubstituted NH group are unstable and their stable representatives have only became accessible in recent years. The tendency of benzazetines to undergo opening of the four-membered heterocycle and isomerization processes was demonstrated. The wide-ranging synthetic possibilities of benzazetines and benzazetes are indicated. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1763–1783, December, 2007.     

A critical examination of the use of the Freundlich isotherm in characterizing molecularly imprinted polymers (MIPs)

The Freundlich isotherm (FI) has previously been shown to be useful in modeling the binding properties of non-covalent molecularly imprinted polymers (MIPs). The advantage of the FI is that it is a heterogeneous binding model that can accommodate and measure the heterogeneity inherent in MIPs. However, it is often difficult to verify whether the FI is an appropriate binding model for a particular MIP because only a narrow portion of the binding isotherm is experimentally measurable. This study takes a critical examination of whether the FI is an appropriate binding model for MIPs and explores its limitations in characterizing a (+)-cinchonine (CN) imprinted polymer and a non-imprinted polymer (NIP). A wider portion of the binding isotherm can be examined by systematically measuring a series of isotherms at different polymer concentrations. This strategy verified that FI can yield an accurate measure of the heterogeneity in the cinchonine MIP and the NIP. However, in cases of extremely high polymer loading, saturation behavior was observed, and the FI yielded inaccurate measures of the binding properties even though the experimental isotherm appears to be well modeled by the FI. Further, these studies indicate that the FI accurately predicts the heterogeneity index for more homogeneous compared to heterogeneous polymers over a wider concentration range but is subject to considerable error as saturation conditions are approached. These studies demonstrate the importance of correctly applying the FI to the lowest concentration portion of the binding isotherm that is experimentally measurable.     

Synthesis of pentafluorophenyl(meth)acrylate polymers: New precursor polymers for the synthesis of multifunctional materials

Pentafluorophenyl acrylate and -methacrylate were polymerized using AIBN as a thermal initiator. The obtained polymers were soluble polymeric active esters that could be used for the preparation of multifunctional polymers. The reactivity of poly(pentafluorophenylacrylate) and poly(pentafluorophenylmethacrylate) towards primary and secondary amines, as well as alcohols was investigated in a quantitative way. Both poly(active esters) reacted satisfactorily with aliphatic primary and secondary amines but only low conversion was found in the case of aromatic amines. Conversions of only 30% were reached when poly(pentafluorophenylacrylate) was treated with one equivalent of alcohol under base catalysis. In time resolved FT-IR studies the rate constants of the polymer analogous reactions were determined.     

Formation of gold branched plates in diluted solutions of poly(vinylpyrrolidone) and their use for the fabrication of near-infrared-absorbing films and coatings

Ribbon-like and branched gold nano- and microstructures were produced by simple heating of diluted aqueous solutions of poly(vinylpyrrolidone) (PVP) and HAuCl4. The reaction was carried out in a one-pot, one-step process at mild temperatures. Modification of the synthesis variables allowed the obtaining of structures with different sizes and branching degrees which formed stable hydrosols with characteristic colors. A mechanism for the growth of the crystals was proposed, based on the aggregation of metal units followed by reorientation and attachment processes facilitated by the presence of low concentrations of the polymer. These anisotropic structures were used to obtain large-area porous coatings on metallic, plastic, and glass substrates and to synthesize homogeneous polymer composites. The resulting gold-modified materials showed an important increase of absorption in the near-infrared (NIR) region of the electromagnetic spectrum, which could find interesting applications in the development of NIR-absorbing filters and coatings.     

Fluorene-based stannylated polymers and their use as recyclable reagents in the Stille reaction

Stannylated polymers based on the polyfluorene backbone have been synthesized and used in the Stille reaction as recyclable reagents, minimizing the generation of toxic tin residues.