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

Hudson, R. L.; Williams, Ffrançon

doi:10.1021/j100497a025

Cited by 20 publications

(4 citation statements)

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“…This type of radical has been previously observed in long-chain n-alkanes14 as well as palmitic acid. 13 No other radical can yield the same total width. This radical probably results from ionization followed by deprotonation from the alkyl side chain.…”

Section: Hc(010ch2ch3 -Hcof + Ch2ch3mentioning

confidence: 99%

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An ESR study of electron reactions with esters and triglycerides

Sevilla¹,

Morehouse²,

Swarts³

1981

J. Phys. Chem.

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Section: Hc(010ch2ch3 -Hcof + Ch2ch3mentioning

confidence: 99%

“…•R' + RCH2C02R' -R'H + RCHC02R' (13) Methyl and ethyl formate anions lead to hydrogen abstraction from the formate group (reactions 2 and 4). In addition, results for methyl formate and perhaps other esters suggest that direct hydrogen abstraction by the ester anion may also be important to ester anion decay (reaction 14).…”

Section: Hc(010ch2ch3 -Hcof + Ch2ch3mentioning

confidence: 99%

An ESR study of electron reactions with esters and triglycerides

Sevilla¹,

Morehouse²,

Swarts³

1981

J. Phys. Chem.

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“…Huddson and Williams studied the radiolysis of carboxylic esters and found that RCOOtHCn-1 H 2 n-1 radicals are photodecomposed into acyl-type radicals by UV irradiation, 13 as…”

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confidence: 99%

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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“…Experiments have shown that photolysis of these radical anions produces ethyl and methyl radicals, respectively, the products expected from 8-scission reactions. 20 The operation of the 8-scission reaction in these ester systems therefore suggests the likely occurrence of ß scission in the carbonate systems.…”

Section: ^C-ocha H5ccrmentioning

confidence: 94%