ESR Studies of Carboxylic Acid- and Ester-Radical Anions Produced by γ-Irradiation at 77°K

Nakajima, Yukihiko; Sato, Shin; Shida, Shôji

doi:10.1246/bcsj.42.2132

Cited by 22 publications

(8 citation statements)

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“…3 In order to elucidate the reactions of carboxylic acid anion radicals in aqueous media we have investigated the formation and reaction of carboxylic acid anion radicals in 12 M LiCl aqueous glasses. 4 In addition, we report results for the radicals produced by electron attachment to several ketones and aldehydes. The results show that radicals formed by electron attachment to carboxylic acids, ketones, and aldehydes can abstract hydrogen atoms from their parent molecules.…”

Section: Introductionmentioning

confidence: 99%

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An ESR study of electron reactions with carboxylic acids, ketones, and aldehydes in aqueous glasses

Sevilla¹,

Swarts²,

Bearden³

et al. 1981

J. Phys. Chem.

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Section: Introductionmentioning

confidence: 99%

“…Soc., 92, 1441 (1970). (4) (a) M. D. Sevilla, J. Phys. Chem., 74, 3366 (1970); (b) Ibid., 74, 2096 (1970); (c) M. D. Sevilla and V. L. Brooks, ibid., 77, 2594 (1973); (d) C. Van Paemel, H. Frumin, V. L. Brooks, R. Failor, and M. D. Sevilla, ibid., 79, 839 (1975).…”

Section: Introductionmentioning

confidence: 99%

An ESR study of electron reactions with carboxylic acids, ketones, and aldehydes in aqueous glasses

Sevilla¹,

Swarts²,

Bearden³

et al. 1981

J. Phys. Chem.

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“…Figure 2 shows the ESR spectra of y-irradiated methyl pivalate at 77 K. A singlet at the center of the spectrum in Figure 2a is due to the anion radicals of methyl pivalate. 15 As shown in Figure 2b, the anion radicals are disappeared by illuminating the sample with visible light, and a part of the anion radicals are converted to methyl radicals. A triplet due to C(CH 3 ) 3 COOCH 2 radicals and a singlet due to C(CH 3 ht=O radicals are also observed in Figure 2b.…”

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confidence: 98%

Thermal and Photo-Induced Reactions of Polymer Radicals in γ-Irradiated Poly(alkyl methacrylate)

Tanaka

Yoshida

Ichikawa

1990

Polym J

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ABSTRACT:Thermal and photo-induced reactions of radical species generated by y-irradiation of poly(methyl methacrylate) and poly(ethyl methacrylate) have been investigated by means of ESR spectroscopy. The y-irradiation at cryogenic temperature leads to the formation of three major radical species, side chain ---COOC.H 2 • + 1 · -anion radicals and---COOCHC._ 1 H 2 • _ 1 radicals, and main chain -CH-radicals. Cation radicals are immediately converted to the neutral radicals by proton transfer to the polymer molecules. Illumination of the polymer anion radicals with visible light leads to electron detachment or the elimination of ester alkyl groups to form alkyl radicals. Illumination with UV light leads to the conversion of the ---COOCHC. _ 1 H 2• _ 1 radicals to acyl-type-C = 0 radicals. Both the---COOCHC. _ 1 H 2.-1 and the-C = 0 radicals are the precursor of scission-type ·qCH3)(COOC.H2.+ 1)CH 2-radicals.KEY WORDS Poly(methyl methacrylate) / Poly(ethyl methacrylate) /Resist/ Lithography / Radiolysis / Degradation / Chain scission / Radical / ESR / Since poly(alkyl methacrylate)s are typical positive-resist materials in deep UV, electron beam and X-ray lithography, many studies have been carried out for clarifying the mechanism of radiation-induced degradation of poly(alkyl methacrylate)s. It is well known that the irradiation of poly(alkyl methacrylate)s with Ionizing radiations results in the formation of scission-type radicals 1 -3 ·c-(CH3)(COOC.H2.+ 1)CH 2-. The formation of the scission-type radicals strongly suggests that the degradation is induced by the reaction of polymer radicals.Since ionization is the main action of ionizing radiations, radiation-generated positive and negative ion radicals are thought to play important roles in the degradation of the polymers. A considerable amount of spectroscopic studies have been carried out for elucidating the nature and the roles of primary ion rad-* To whom correspondence should be addressed. icals in the degradation of the polymers. 4 -10 However, there have been few consistencies between investigators even for the spectroscopic assignment of the ion radicals. We have recently made the pulse radiolysis studies of poly(alkyl methacrylate) solutions, and determined the optical absorption bands of the polymer anion radicals. 11 We have also made the ESR and electron spin echo studies of yirradiated poly(methyl metacrylate) (PMMA) and found that the y-irradiation at cryogenic temperature leads to the formation of three major radical species, side chain -COOCH 3 ·-anion radials and -COOCH 2 radicals, and main chain -CH-radicals. 12 Upon annealing the polymer to room temperature, the -COOCH 2 radicals were disappeared accompanied by the formation of scission-type ·qcH 3 )(COOCH 3 )CH 2 -radicals, which suggests that the -COOCH2 radicals are respon-835

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“…Since it was necessary to record the spectra at high power to maximize the signals from the ethyl radical relative to those of the other radical components, this could explain the previous failure to recognize the formation of ethyl radicals in this photobleaching reaction. 3,6 The aforementioned results for methyl propionate and ethyl acetate establish that the photobleaching of the radical anion RC(0")0R' by visible light generates the alkyl radical R'• by a process of ß scission as represented by (1) in the reaction scheme below.…”

mentioning

confidence: 87%

“…The spectra in (b) were recorded at one-half of the spectrometer gain used in (a). OCXY X and Y = H and/or alkyl groups (1) (2)…”

mentioning

confidence: 99%

An electron spin resonance study of the photolysis of trapped radicals in .gamma.-irradiated carboxylic esters at 77-87 K

Hudson¹,

Williams²

1978

J. Phys. Chem.

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Sir: Although several ESR studies have shown that the photolysis of trapped radicals in -irradiated carboxylic esters, RC(0)0R', at (or near) 77 K leads to the formation of alkyl radicals,1™3 the literature is often confusing and even contradictory on the question of whether R• or R'• is the product radical. Thus, the UV photobleaching of -irradiated ethyl acetate and methyl pivalate is reported to give the methyl radical in each case despite the different locations of the methyl group (R and R', respectively) in the parent esters,1 whereas another study of -irradiated methyl pivalate indicates that the tert-butyl radical is generated on exposure to UV light.2 In view of these apparently conflicting reports, we have reexamined the reactions occurring on the photobleaching of -irradiated carboxylic esters. We now wish to present evidence showing that alkyl radicals are produced on photobleaching

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ESR Studies of Carboxylic Acid- and Ester-Radical Anions Produced by γ-Irradiation at 77°K

Cited by 22 publications

References 10 publications

An ESR study of electron reactions with carboxylic acids, ketones, and aldehydes in aqueous glasses

An ESR study of electron reactions with carboxylic acids, ketones, and aldehydes in aqueous glasses

Thermal and Photo-Induced Reactions of Polymer Radicals in γ-Irradiated Poly(alkyl methacrylate)

An electron spin resonance study of the photolysis of trapped radicals in .gamma.-irradiated carboxylic esters at 77-87 K

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