Electron spin resonance study of polyglycols

Thryion, F. C.; Baijal, M. D.

doi:10.1002/pol.1968.150060307

Cited by 10 publications

(2 citation statements)

References 14 publications

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“…7(b) their simulated absorption spectra without R 2,3 radicals are shown. The obtained HFS proton parameter (¾1.6 mT) is similar to that reported for the ž CH 2 -O-¾ radical after the polymer chain degradation of polyglycole under irradiation at 77 K. 20 According to the spectroscopic results represented before a probable photochemical reaction pathway of radical formation and degradation with high quantum energy UV irradiation of NMMO at 77 K is suggested (Scheme 2). At the first step (I) radical R 1 is formed under irradiation as a result of the ring degradation by a first-order reaction pathway.…”

Section: N-methylmorpholine-n-oxide and Cellulose/n-methylmorpholine-supporting

confidence: 60%

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Konkin

Wendler

Roth

et al. 2006

Magnetic Reson in Chemistry

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The processes of radical formation in N-methylmorpholine-N-oxide monohydrate (NMMO) and cellulose/NMMO solutions were studied by ESR at 77 K under high-power UV (lambda = 248 nm) excimer laser flash photolysis. Radicals mainly generated were attributed to the nitroxide type radicals -CH2-NO*-CH2- and -CH2-NO*-CH3 at the first step and methyl *CH3 and formyl *CHO radicals at the second step of the photoreaction. Kinetic studies of these radicals revealed that formation and recombination rates of the radicals depend on the cellulose concentration in cellulose/NMMO solutions and the concentration of additional ingredients, e.g. Fe(II) and propyl gallate. Even at frozen state temperature, acceleration or quenching of radical reaction processes was found. The proposed scheme of UV light-induced NMMO degradation during irradiation based on ESR data correlates well with independently obtained results based on high-performance liquid chromatography (HPLC). The analysis of degradation products by HPLC, e.g. aminoethanol and acetaldehyde, supports the assumption concerning a radical-initiated ring opening of NMMO.

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Section: N-methylmorpholine-n-oxide and Cellulose/n-methylmorpholine-supporting

confidence: 60%

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Konkin

Wendler

Roth

et al. 2006

Magnetic Reson in Chemistry

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“…It is worthwhile noting that information on the radical products of PEO radiolysis is virtually absent despite the chemical structure of elementary unit of this polymer is quite simple. To our knowledge, the ESR spectra of γ -irradiated polyglycols (PEO analogues) were reported only by Thyiron and Baijal [11], who also observed a triplet signal with a splitting of 1.7 mT. This signal was ascribed to -é-ç 2 radicals resulting from the C-C bond scission in the polymer chain.…”

Section: Resultsmentioning

confidence: 88%

Radiolysis of Aqueous Solutions of Poly(ethylene oxide) at 77 K

2005

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1 Investigations of the radiolysis of aqueous solutions of polymers have attracted considerable interest, which is mainly due to the development of the radiation-chemical synthesis of hydrogels. This method of synthesis implies irradiation of aqueous solutions of crosslinkable polymers, such as poly(vinyl alcohol), polyvinylpyrrolidone, poly(ethylene glycol), and poly(ethylene oxide). The process of macrochain crosslinking resulting in the formation of hydrogels upon γ -irradiation of aqueous solutions of polymers is initiated by water radiolysis transient products, first of all, hydroxyl radicals. The interaction of OH radicals with a macromolecule leads to hydrogen atom abstraction followed by recombination of macroradicals. As a result, the polymeric chains are crosslinked to form a three-dimensional polymeric network, that is, a hydrogel.Poly(ethylene oxide) (PEO) is one of the polymers that are commonly used for the synthesis of hydrogels. The PEO-based hydrogels possess a set of properties that make these materials suitable for biological (separation and purification of proteins), medical (drug delivery systems of prolonged action and wound dressing), chemical (separation of metal cations), and other applications (the examples may be found elsewhere [1][2][3][4][5]). Recently, we have demonstrated the feasibility of synthesis of a PEO hydrogel with a physically immobilized crown ether, which can selectively bind metal cations due to specific complex formation [6]. Although the radiation-chemical synthesis of PEO hydrogels was investigated in numerous works, to our knowledge, there are a few publications on the radiolysis of PEO and its aqueous solutions. Zainuddin et al. [7] have 1 E-mail: olzak@mail.ru shown that both crosslinking and scission of polymer chains occur simultaneously upon γ -irradiation of solid poly(ethylene oxide) in the absorbed dose range up to 20 kGy. In this case, the prevalence of crosslinking or scission depends on both absorbed dose and molecular weight of the polymer. On the other hand, the radiolysis of dilute aqueous PEO solutions was studied by pulse radiolysis [8,9], which made it possible to determine the rate constants for the reactions of OH radicals, H atoms, and hydrated electrons in this system. These studies have demonstrated that hydroxyl radicals are the main precursors of macroradicals from PEO. However, data on the nature and radiation-chemical yields of intermediates resulting from the radiolysis of PEO and its aqueous solutions are very scarce.Detailed information on the composition and yields of radical products of radiolysis and their reaction kinetics can be obtained in low-temperature ESR spectroscopic studies. In this case, it is possible not only to identify the radicals trapped after irradiation of a frozen solution, but also to follow the character of their postirradiation transformations occurring upon gradual freezing-out of molecular mobility. Note that the frozen solutions of water-soluble polymers are complex microheterogeneous systems and, thus, the r...

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Electron spin resonance study of poly‐3,3‐bis(chloromethyl) oxetane irradiated with electron beams and ultraviolet light

Tsuji

Hayashi

Okamura

1970

J. Polym. Sci. A‐1 Polym. Chem.

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Poly‐3,3‐bis(chloromethyl)oxetane (poly‐BCMO) was irradiated at −196°C with electron beams and ultraviolet light, and observed ESR spectra were compared. A three‐line spectrum (coupling constant of about 21 gauss) and a two‐line spectrum (coupling constant of about 18 gauss) were observed after irradiation with electron beams in vacuo. They were attributed to free radicals and respectively. On the other hand, a three‐line spectrum (coupling constant of about 20 gauss) and an asymmetric singlet spectrum were observed after ultraviolet irradiation in vacuum. They were assigned to free radicals and CH2O·, respectively. Mechanisms of radical formation were discussed in each case. When poly‐BCMO was irradiated with electron beams at −196°C in the presence of air, peroxy radicals were produced after subsequent treatment at −78°C. The reaction between alkyl radicals and oxygen molecules was found to be diffusion‐controlled.

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Electron spin resonance study of polyglycols

Cited by 10 publications

References 14 publications

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Radiolysis of Aqueous Solutions of Poly(ethylene oxide) at 77 K

Electron spin resonance study of poly‐3,3‐bis(chloromethyl) oxetane irradiated with electron beams and ultraviolet light

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