Radiation chemistry of polymers

Results of basic and applied research in radiation chemistry of polymers in Russia and Belarus for the last 5–10 years are presented.     

Radiation chemistry of poly(propylene oxide)

Atactic, isotactic, and optically active poly(propylene oxides), PPOx, were irradiated with both γ-rays and electron beams. Up to a dose of 37 Mrad no change could be detected in the optical activity. G values for hydrogen evolution decreased as compared to polypropylene in about the same ratio as G(H₂) of polyoxymethylene decreased as compared to polyethylene. G values for crosslinking and scission, estimated by means of gelation theories of Saito and Inokuti, were found to be greater for isotactic than for atactic PPOx. The behavior of transient infrared and ultraviolet absorption bands is discussed. Intrinsic viscosity data indicate a rapid initial chain degradation whereas CO gas and OH group production is linear with dose. Evidence for the conversion of one type of free radical to another on heating an irradiated sample from 77°K to room temperature is based on the behavior of transient infrared and ultraviolet absorption bands.     

Radiation chemistry of Cu(II) tetrasulfophthalocyanine in water-methanol system

The effect of ionising radiation on copper(II) phthalocyanine 3,4′,4′′,4′′′ tetrasulfonic acid, tetrasodium salt (Cu(II)tspc^4-) in aqueous as well as in water-methanol solutions has been studied. The determined yields of complex decomposition (measured on the basis of absorption decay) depend on the composition of matrices and the dose applied. The rate constant of electron scavenging by Cu(II)tspc^4-, k = (1.3 ± 0.1) × 10¹⁰ M^-1 s^-1 in methanol-water (2:8 v/v) solutions has been determined using the pulse radiolysis technique. The rate constant k = (1.16 ± 0.1) × 10¹⁰ M^-1 s^-1 of scavenging of OH radicals applying the competion method with p-nitrosodimethylaniline (pNDA) has been determined in aqueous solutions.     

Radiation chemistry of aqueous poly(ethylene oxide) solutions. I

The γ radiolysis of aqueous high molecular weight poly(ethylene oxide) solutions has been studied. The crosslinking and eventual gelation of these solutions appears to occur via an indirect effect. Solubility measurements on the gelled solutions showed that the ratio of crosslinking to degradation is about four. G(H₂) increased from 1.3 in neutral solutions to 3.5 in 0.1N HCl solutions. In heavy water solutions, HD is the major gaseous product. Solvated electrons are not important precursors to hydrogen at neutral pH. Intramolecular crosslinking appears to be an important phenomenon in solutions of high molecular weight polymers.     

Plasma chemistry of polymers

Ohne Zusammenfassung

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Plasma chemistry of polymers

     

Radiation chemistry of tetramethylgermane

A study of the ⁶⁰Co γ-irradiation of tetramethylgermane is reported. The major products are identified and their yields given. Both carbon-hydrogen and carbon-germanium bond scission occur. Hydrogen and methane are the major gaseous products. Ethyltrimethylgermane, hexamethyldigermane, bis(trimethylgermyl) methane and bis(trimethylgermyl)ethane are the major heavier products. The total yield of products indicates that the yield of disappearance of tetramethylgermane, G[—Ge(CH₃)₄], is 10.2 molecules per 100 eV absorbed. An (unidentified) product is formed which captures electrons.     

Radiation chemistry of actinides

The paper presents data on the development of a mathematical model describing the radiation-chemical behaviour of plutonium in 3–6 mol/l HNO₃ with uranium present and absent. Using experimental data on the kinetics of Pu(VI) reduction and Pu(IV) oxidation, and comparing them with the calculated values, we succeeded in finding the previously unknown rate constants of many reactions between plutonium ions and HNO₃ radiolysis products, between plutonium ions and between plutonium ions and uranium ions. The mechanism of the radiation-chemical processes has been established.     

Review: Lanthanide coordination chemistry: from old concepts to coordination polymers

Because of their remarkable and unmatched optical and magnetic properties, the lanthanides are under the limelight when it comes to high technology. These elements are used in strategic applications such as optical glasses and lasers, telecommunications, lighting and displays, magnetic materials, hard-disk drives, security inks and counterfeiting tags, catalysis, biosciences, and medicine, to name but a few. Long considered as minor actors in transition metal chemistry, they have now gained respect from coordination chemists who insert them into sophisticated functional and polyfunctional molecules and materials. This mini review focuses on trivalent lanthanide ions and first summarizes their basic properties. Then some classical aspects of their coordination chemistry are discussed, followed by macrocyclic chemistry, supramolecular chemistry, and self-assembly processes. The last part of this contribution deals with coordination polymers and hybrid materials including potential applications.     

Organic polymers achieving smart room-temperature phosphorescence

<正>Room-temperature phosphorescence (RTP) has drawn widespread attention recently owing to the unique long-lived triplet excited states and potential applications in lightemitting diodes (LEDs)[1], optical imaging [2], photodynamic therapy [3], and information security [4]. Particularly, RTP materials can effectively utilize the triplet excitons     

Synthesis of polyarylenephthalides prospective as smart polymers

The data on the synthesis of polyarylenephthalides, their analogs, and derivatives are surveyed. The main attention is given to the synthesis of polyarylenes through the polycondensation of pseudoacid chlorides according to several variants, predominantly via the self-condensation of pseudoacid chlorides, which may be depicted by the general scheme

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(?RH is the radical of aromatic or heterocyclic polynuclear hydrocarbon.). The reaction affords polyarylenephthalides (I) (X = CO, Y = O), polyarylenephthalimidines (II) (X = CO, Y = NR₁, where R₁ is an aromatic hydrocarbon), and polyarylenesulfophthalides (III) (X = SO₂, Y = O). Polymers I and II hold promise for designing thermostable, heat-(T _g ≥ 420–470°C) and chemoresistant, and functional materials. One should distinguish the valuable functional properties of polymers I and III that make them prospective as smart polymers, namely, the switching effect induced by temperature, pressure, and electric and magnetic fields along with changes in color, electro-and photoluminescence. Owing to the presence of sulfophthalide groups, polymers III are candidates for use as latent polyelectrolytes. With consideration for the foregoing reasoning, phthalide-containing polyarylenes of several other classes, namely, polyaryleneketones, poly(arylene ether ketones), polyarylates, oligomer resols, and crosslinked systems on their basis, which are prospective as smart polymers, have been synthesized.

     

Radiation modification of semicrystalline polymers

Three problems of the radiation modification of polymers are dealt with. Different methods of grafting are compared with respect of the formation of true graft copolymer and homopolymer in the polyethylene-styrene system; the prevention of the penetration of monomer by grafting polytetrafluoroethylene is shown; the mechanical properties of crosslinked ethylene polymers below and above the melting point are discussed.     

Physical organic chemistry of supramolecular polymers

Unlike the case of traditional covalent polymers, the entanglements that determine properties of supramolecular polymers are defined by very specific, intermolecular interactions. Recent work using modular molecular platforms to probe the mechanisms underlying mechanical response of supramolecular polymers is reviewed. The contributions of supramolecular kinetics, thermodynamics, and conformational flexibility to supramolecular polymer properties in solutions of discrete polymers, in networks, and at interfaces, are described. Molecule-to-material relationships are established through methods reminiscent of classic physical organic chemistry.     

天然高分子/聚丁二酸丁二醇酯共混物研究进展

聚丁二酸丁二醇酯(PBS)是一种热塑性脂肪族聚酯,因力学和生物降解性等性能良好而具有广泛应用前景,但仍存在拉伸强度和生物降解速率低,成本高等缺陷,限制了其应用。通过物理改性是提高其性能和应用领域的重要研究方向之一。本文综述了近年天然高分子/PBS共混物制备和性能研究,并对天然高分子/PBS共混物的发展作了总结和展望。     

Radiation chemistry education in Australia

A segment on radiation chemistry should be included in every course on nuclear science because of its unique role and its being relatively far removed from nuclear explosives. Experience of courses at different levels is outlined. Particular attention is given to the use of radiation chemical techniques in the training of postgraduate research students.Honorary AINSE Fellow, formely Post Retirement Fellow, ANSTO Isotope Technology.     

Radiation chemistry of aqueous poly(ethylene oxide) solutions. II. Highly purified samples

The radiation chemistry of highly purified, rigorously degassed aqueous solutions of poly(ethylene oxide) is markedly different from solutions not so treated. Gelation doses are lower in the purified samples by almost two orders of magnitude. Degradation is unimportant in dilute solutions. The very broad molecular weight distribution as well as the very high molecular weight of these polymers makes the interpretation of the results difficult. Neither gel dose measurements nor solubility measurements give valid crosslinking yields. The crosslinking yield is highly concentration-dependent.     

Robust and smart hydrogels based on natural polymers

This review summarizes recent progress of the robust and smart hydrogels prepared from natural polymers including polysaccharides,proteins,etc.These hydrogels exhibit outstanding mechanical properties due to their nanofibrous aggregated microstructures and special crosslinking networks.Furthermore,these hydrogels show some smart stimuliresponsive behaviors triggered by pH,temperature,light,electricity and magnetism.Hopefully,these hydrogels derived from natural polymers with inherent biodegradation and biocompatibility have great application potential in the fields of biomedicine,tissue engineering,soft robots and bio-machine.     

ESR application to radiation chemistry of polymers

Important results obtained in our group in the field of ESR application to the study of irradiated polymers are summarized. They are the analysis of the decay reaction of the free radicals, spur-like trapping of the free radicals and the related discussions. A diffusion controlled bimolecular reaction scheme was a good way of analyzing the data of the decay reaction. Power saturation phenomenon of ESR spectra of the free radicals showed a circumstance of the spur-like trapping of the free radicals in irradiated polyethylene. The phenomenon of spur-like trapping was quite consistent with the interpretation of the decay reaction of the free radicals.