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).     

Statistical mechanics of diffusion in polymers: Conductivity and electroosmosis in ion exchange membranes

The dependency of swelling of an ion exchange membrane and its ion-exchange capacity on the conductivity and electroosmosis are investigated. The analysis is based on a rigorous statistical mechanics theory employing the formalism of the generalized Nernst–Planck equation in the dusty gas membrane model. The simulation uses binary diffusivities computed from experimental data. Some unexpected conclusions can be drawn from the computed transport characteristics: at constant swelling of the polymeric membrane the equivalent conductivity decreases with the exchange capacity; the enhancement of conductivity by electroosmosis is rather poor, in all cases smaller than 15 %; conductivity of the material is more dependent on its exchange capacity than on swelling.

The calculations confirm that an optimized membrane with low electroosmosis is a highly charged membrane with low swelling. We show that the simple binary theories lead to wrong predictions of the conductivity even qualitatively. Finally, we propose a simple empirical theory, compatible with the generalized Nernst–Planck equation, where the diffusivities increase exponentially with swelling.     

Metal ion separations with proton-ionizable crown ethers and their polymers

Abstract

Lipophilic crown ethers with pendent proton-ionizable groups are novel complexing agents for use in metal ion separations by solvent extraction. For a series of structurally related, lipophilic dibenzocrown ether carboxylic acids, the efficiency and selectivity of competitive alkali metal cation extraction for aqueous solution into chloroform is found to be strongly influenced by the crown ether ring size and the lipophilic group attachment site. Reaction of dibenzocrown ether carboxylic acids with formaldehyde in formic acid produces condensation polymers which possess both ion-exchange and cyclic polyether binding sites for metal ion complexation. These resins exhibit excellent exchange kinetics for competitive alkali metal cation sorption from aqueous solution and subsequent stripping and may be used in concentrator columns for the recovery of these metal ions from very dilute aqueous solution. Cation selectivity in the sorption and stripping steps is controlled by the structure of the crown ether monomer unit.     

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.     

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.     

Synthesis and characterisation of sulfonic acid-containing ion exchange membranes based on hydrocarbon and fluorocarbon polymers

Radiation-induced graft copolymerisation has been used to modify polymers with styrene to prepare pre-cursor copolymers that can be subsequently functionalised to produce ion exchange membranes. This paper describes the processes of simultaneous and pre-irradiation graft copolymerisation of styrene to modify hydrocarbon and fluorine-containing polymers and their sulfonation to produce hydrophilic membranes. The effect of varying the grafting conditions and their characterisation by ion exchange capacity, electrolytic resistivity and equilibrium water content is reported.     

Perfluorinated anion exchange membranes: Preparation and preliminary tests of dialysis

Using the preirradiation technique a kinetic study of the grafting of the 4-vinyl pyridine (V₄P) and an aliphatic ammonium monomer (ALAM) onto the copolymer film of ethylene–tetrafluoroethylene (ETFE) has been performed. The influence of dose, temperature, and concentration of monomer, reticular agent, and inhibitor were investigated. The results are discussed on the basis of the interactions between monomer diffusibility and viscosity of the medium. The characteristics of some membranes were determined. Their applicability to the recovery of acid by dialysis is demonstrated.     

Preparation and characterization of organotin-oxomolybdate coordination polymers and their use in sulfoxidation catalysis

The organotin-oxomolybdates [(R(3)Sn)(2)MoO(4)].n H(2)O (R=methyl, n-butyl, cyclohexyl, phenyl, benzyl) have been prepared and tested as catalysts for the oxidation of benzothiophene with aqueous hydrogen peroxide, at 35 degrees C and atmospheric pressure. In all cases, the 1,1-dioxide was the only observed product. The kinetic profiles depend on the nature of the tin-bound R group and also on the addition of a co-solvent. For the tribenzyltin derivative, the apparent activation energies for sulfoxidation as a function of the co-solvent are in the order 1,2-dichloroethane (5 kcal mol(-1))相似文献   

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.     

Syngas cleaning with nano-structured micro-porous ion exchange polymers in biomass gasification using a novel downdraft gasifier

Sulphonated nano-structured micro-porous ion exchange polymers,known as sulphonated PolyHIPE Polymers(s-PHPs) were used in syngas cleaning to investigate their impact on tar composition,concentration and dew point depression during the gasification of fuel cane bagasse as a model biomass.The results showed that the s-PHPs used as a secondary syngas treatment system,was highly effective at adsorbing and reducing the concentration of all class of tars in syngas by 95%-80%which resulted in tar dew point depression from 90℃to 73℃.It was shown that tars underwent chemical reactions within s-PHPs,indicating that tar diffusion from syngas was driven by chemical potential.It was also observed that s-PHPs also captured ash forming elements from syngas.The use of s-PHPs in gasification as well as in an integrated thermochemical biorefinery technology is discussed since the tar loaded s-PHPs can be used as natural herbicides in the form of soil additives to enhance the biomass growth and crop yield.     

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.     

New narrow-band-gap thiazoloquinoxaline-containing polymers and their use in solar cells with bulk heterojunction

Two new regioregular polymers P1 and P2 with structure of type D–A1–D–A2 have been prepared. The polymers exhibit strong light absorption in the range 300–1100 nm and have band gaps of 1.09 and 1.11 eV, respectively. The HOMO and LUMO energies for P1 and P2 are–5.08/–3.81 and–5.16/–3.85 eV, respectively. Polymer solar cells (PSC) based on P1: PC₇₁BM (1: 2, v/v) and P2: PC₇₁BM (1: 1, v/v) have open-circuit voltage V _oc, short circuit current J _sc, and efficiency of 0.79 and 0.84 V, 8.32 and 9.54 mA/cm², 3.5 and 4.7%, respectively. The PSC based on P2 exhibits higher characteristics due to the presence of fluorine atoms in the structure: their strong electron-withdrawing properties decrease the HOMO level of polymer P2 as compared with that of P1, which increases the V _oc value. Moreover, the formation of additional S???F contacts leads to the growth of ordering and crystallinity of polymer P2 as compared with P1, which favors an increase in the values of J _sc and filling factor.     

Preparation of ion exchange resin based elemental standards for use in activation analysis

Various methods of preparing standards for activation analysis have been reported in the literature. This paper describes the feasibility of preparing ion exchange resin based standards containing predetermined levels of ions. Using a solution of known initial concentration of the ion, and given the value of its distribution coefficient, it is possible to predict the resin concentration that will be obtained. Resins containing ppm levels of copper and manganese have been prepared and their stabilities evaluated over a period of time. The feasibility of preparing a multielement standard has been studied with five rare earth elements (La, Ce, Sm, Eu and Dy).     

Efficient and versatile synthesis of star polymers in water and their use as emulsifiers

Core cross-linked star polymers of low polydispersity were efficiently prepared in high yield by RAFT-mediated emulsion and dispersion polymerizations in water at high solid content. These star polymers were demonstrated to be effective emulsifiers, and the emulsion was successfully used as template to fabricate polymer particles.     

Cyclodextrin polymers in the pharmaceutical industry

The potential applications of cyclodextrin polymers (soluble and insoluble ones) in the pharmaceutical industry are reviewed. The soluble polymers are good solubilizers of drugs thus enhancing their bioavailability. When applied topically the insoluble bead polymer accelerates the healing of burns and ulcers. It can also be used for chromatography and to remove certain components from mixtures. The insoluble ground polymer is an effective tablet disintegrant in direct compression systems as well as in formulations made by wet granulation.Lecture, presented at the meeting Anwendungsmöglichkeiten von Cyclodextrin in der pharmazeutischen Industries, Berlin, 21/22 September 1987.