The formation of dibenzoyl peroxide by photooxidation of benzil in a polymer film

Lukáč, Ivan; Kósa, Csaba

doi:10.1002/marc.1994.030151204

Cited by 22 publications

(30 citation statements)

References 10 publications

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“…(2 -7). Reaction proceeds from the excited triplet state of BZ ( 3 BZ) [9][10][11][12] . Besides photooxidation, quenching of 3 BZ with ground state oxygen ( 3 O 2 ) is also possible 10) .…”

Section: Resultsmentioning

confidence: 99%

“…The photoinitiated conversion of benzil to benzoyl peroxide in aereated polymer films 12) seems to be a general phenomenon. It represents an interesting example of the importance of environment on substrate reactivity 18) .…”

Section: Discussionmentioning

confidence: 99%

“…A 1,4-biradical involving a molecule of oxygen attached to one of the carbonyl groups was proposed as the key intermediate 11) . Recently we reported that BZ can be converted almost quantitatively to BP in aerated PS or PMMA by irradiation at k A 400 nm (i. e., the long wavelength edge of the n e p* absorption band) 12) . Here, we examine more carefully this surprising and important change of reaction course in PS, PMMA and three other polymer matrices.…”

Section: Introductionmentioning

confidence: 99%

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Relative rates of photooxidation of benzil to benzoyl peroxide in various polymer matrices

Kósa

Lukáč²,

Weiss

1999

Macromol. Chem. Phys.

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SUMMARY: Benzil (BZ), 16 wt.-%, has been irradiated (A 400 nm) at ambient temperature in aerated polystyrene (PS), poly(methyl methacrylate) (PMMA), polycarbonate (PC), polysulfone (PSF) and poly(vinyl chloride) (PVC) films. The rate of BZ consumption, leading primarily to the formation of benzoyl peroxide, was followed by infrared spectroscopy. The rate of reaction is sensitive to the nature of the glassy polymer matrix and decreases in the order: PS A PC A PVC A PSF A PMMA. The dependence of the rate of BZ consumption on the concentration of dissolved molecular oxygen in the polymer matrices is rather complex. A kinetic treatment, assuming steady-state conditions, leads to the conclusion that the sum of the rates of bimolecular formation of benzoyl peroxide and quenching of BZ triplets by molecular oxygen, (k ox + k q )[ 3 O 2 ], represents only 0.8 -13% of the sum of the unimolecular rates of radiationless and radiative deactivation (including k p , the pseudo first-order rate constant for reaction of BZ triplets with the polymer), (k d + k ph + k p ), in the various polymer matrices.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Relative rates of photooxidation of benzil to benzoyl peroxide in various polymer matrices

Kósa

Lukáč²,

Weiss

1999

Macromol. Chem. Phys.

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“…In this way it is possible also to crosslink polymers, which undergo main chain scissions, when the low-molecular-weight peroxides are decomposed in their matrix, e.g., polystyrene. 13 Despite some suggestions, 7,8 the precise mechanism of photoperoxidation of BZ has not been unequivocally established.…”

Section: Introductionmentioning

confidence: 99%

“…6 BZ can be converted almost quantitatively to BP in aerated amorphous glassy polymer films, below glass transition temperature by irradiation at Ͼ 400 nm (i.e., the long wavelength edge of the n 3 * absorption band wherein BP does not absorb) (Scheme 1). 7,8 Covalently attached BP pendant groups have also been formed from BZ pendant groups by irradiation of copolymer films in air. 9 -12 Decomposition of covalently attached BP pendant groups leads to crosslinking of the polymer.…”

Section: Introductionmentioning

confidence: 99%

Photooxidation of benzil groups in the presence of hindered amine stabilizers in the polystyrene film

Kósa

Mosnáček

Lukáč

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:The photoperoxidation at Ͼ 400 nm of benzil (BZ) groups with the air oxygen to benzoyl peroxide (BP) groups in the polystyrene matrices was investigated in the presence of hindered amine stabilizer (HAS). HAS was used as a free molecule or was bound in combined molecule with BZ. HAS was in the form of parent amine as 2,2,6,6-tetramethyl-4-hydroxypiperidine (TMP) and in the form of stable nitroxyl radical 1-oxo-2,2,6,6-tetramethyl-4-hydroxypiperidine (NO). Both HAS forms effected the photooxidation of BZ structures. The main product of the photooxidation in the presence of parent amine TMP as well as in its absence is benzoyl peroxide (BP). The rate of BZ consumption increases in the presence of TMP. Irradiation of BZ in the presence of sufficient concentration of freely added NO results only in the formation of benzoic acid esters and benzoic acid, which are the main decomposition products of BP. The benzoic acid esters/benzoic acid ratio increases with the increasing concentration of NO. Bounding of BZ and TMP into one molecule (BZNH) results in slower dicarbonyl depletion, as compared with the case when mixture of BZ and TMP was used. Very slow depletion of BZ carbonyl absorption was observed in the case of bounded BZ and NO in one molecule (BZNO), in comparison with the mixture of free NO and BZ. In the case of BZNO, an effective intramolecular quenching of BZ excited triplet states with NO structures proceeds. Steady stay and dynamic emission (phosphorescence) measurements also show an effective quenching of BZ excited states by unbounded or bounded NO.

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New Insights in the Influence of Oxygen on the Photocrosslinking of Silicone Acrylates

Mller

2000

Organosilicon Chemistry IV

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The formation of dibenzoyl peroxide by photooxidation of benzil in a polymer film

Cited by 22 publications

References 10 publications

Relative rates of photooxidation of benzil to benzoyl peroxide in various polymer matrices

Relative rates of photooxidation of benzil to benzoyl peroxide in various polymer matrices

Photooxidation of benzil groups in the presence of hindered amine stabilizers in the polystyrene film

New Insights in the Influence of Oxygen on the Photocrosslinking of Silicone Acrylates

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