Peculiarities of the elementary stages of radiation-induced polymerization of monomers on the surface of solids

Bruk, M.A.; Павлов, С.А.; Isaeva, G. G.; Yunitskaya, E.Ya.

doi:10.1016/0014-3057(86)90113-8

Cited by 6 publications

(4 citation statements)

References 2 publications

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“…In porous materials, the general concept that comes out of these studies is that energy deposited in the bulk of the solid is transferred to the surface, there creating chemistry . The reactions studied include oxidation and decomposition of organic adsorbates and polymerization of various vinyl monomers. − In general, reactive intermediates and reaction mechanisms involved in the chemical reactivity of the above solid systems are not clearly understood, except for some tentative propositions drawn from the analysis of final products. A detailed knowledge of the formation of transient intermediates and the structure−property relationship for these solids is essential in the design and preparation of specific catalysts.…”

Section: Introductionmentioning

confidence: 99%

Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Milosavljevic

Thomas

2003

J. Phys. Chem. B

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Radiolysis of γ-alumina produces electrons, e -, and positive holes, h + . These species rapidly migrate to the surface to produce products of surface adsorbed compounds. The electrons are also trapped by surface OH groups giving rise to short-lived (<10 µs) trapped electrons, e t -. Heating the γ-Al 2 O 3 produces Lewis acid sites and decreases the OH content of the surface. Such material produces much lower yields of trapped electrons, as ethen reacts predominantly with the Lewis acid sites. Hydrogen gas is produced on radiolysis of γ-Al 2 O 3 via H atom formation from e -. The H atoms may recombine, producing H 2 , or react with surface adsorbed materials (e.g., pyrene) to produce H atom adducts. The basic radiation chemistry is similar to that observed in zeolites (but not SiO 2 ), where ionization predominates. These studies illustrate for the first time the production of electrons in a γ-Al 2 O 3 surface and the consequent two-dimensional kinetics of these species on the surface.

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Section: Introductionmentioning

confidence: 99%

Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Milosavljevic

Thomas

2003

J. Phys. Chem. B

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“…It was found that excitation energy is transferred from solid particles to solid surfaces, and significant chemistry occurs at interfaces . The reactions studied include oxidation and decomposition of organic adsorbates and polymerization of various vinyl monomers. − Reactive intermediates and reaction mechanisms involved in the chemical reactivity of the above solid systems are not clearly understood, except for some tentative propositions drawn from the analysis of final products. Detailed knowledge of the formation of transient intermediates and the structure−property relationship for these solids is essential in the design and preparation of specific catalysts.…”

Section: Introductionmentioning

confidence: 99%

Surface Chemistry Induced by High Energy Radiation in Silica of Small Particle Structures

1997

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Spectroscopic techniques are used to investigate energy transfer and radiation-induced reactions on the surfaces of particulate silicas. Upon subjection to high energy radiation, hydrogen atoms are produced with significant yields in all silica samples pretreated at 150 °C, for an example, G(H) = 4.2 in silica gel Davisil 60. Subsequent hydrogen addition to aromatic adsorbates such as pyrene, N,N-dimethylaniline, and methyl viologen (MV2+) proceeds on the surface in competition with the hydrogen dimerization, leading to the formation of their H adducts. Hydrogen scavenging studies revealed that such addition reactions are heterogeneous in porous silica gel with contributions from a fast intrapore reaction within several nanoseconds and a much slower diffusion influenced interpore process over many microseconds. The efficient capture of H atoms by pyrene at a small percentage of surface coverage suggests that hydrogen is produced at the specific sites where pyrene adsorbs. Electron scavenging by CHCl3, Cd2+, and MV2+ leads to a suppression of H addition and an enhanced positive charge transfer to pyrene. Pretreatment of silica samples at 600 °C gives rise to increased ionic products of aromatic adsorbates, concomitant with decreased hydrogen production. These experimental observations are understood in terms of an exciton model. By comparison with the electronic processes in bulk silica materials, it is shown that surface plays a major role in the relaxation of excitation and the activation of adsorbate chemistry.

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“…As such, and along with alumina and zeolites, it has been of interest as a support for high-energy radiation studies. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Extensive photochemical studies are also reported on oxide surfaces. [16][17][18][19][20] The photoinduced reactions of free radicals, radical ions, and excited states have all been studied on these surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…High surface area silica is one of the most widely used catalyst supports. As such, and along with alumina and zeolites, it has been of interest as a support for high-energy radiation studies. − Extensive photochemical studies are also reported on oxide surfaces. − The photoinduced reactions of free radicals, radical ions, and excited states have all been studied on these surfaces. From the view of kinetics the fractal, rigid, and heterogeneous nature of these surfaces necessitate a careful consideration of the detailed nature of the reactions on these surfaces.…”

Section: Introductionmentioning

confidence: 99%

Quenching of Excited States of Pyrene by Tetranitromethane on SiO₂ Surfaces: Effect of Reaction Temperature, Silica Pore Size, and Surface Silanol Content

and

Thomas

1999

Langmuir

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Quenchers which adsorb strongly to the silica gel surface show limited quenching of the excited states of coadsorbed donors, and when quenching does occur it is predominantly static quenching. This is observed for several quenchers including nitromethane, tetranitromethane, and methyl viologen. The strong adsorption of tetranitromethane (TNM) to the surface silanol groups is indicated by the significant adsorption from cyclohexane solutions and the lack of any desorption with continuous evacuation of the sample after addition from solution or by vapor transfer. The strong adsorption of TNM is observed in the quenching characteristics of several adsorbed donors including the singlet and triplet excited states of pyrene. The quenching mechanism is partially determined by the binding characteristics of the coadsorbed electron acceptors and partially by the surface structure of the porous silica gel support material. Removing the high density of surface silanol groups changes the adsorption characteristics reducing the adsorption efficiency of both pyrene and TNM. The photophysics and photochemistry between coadsorbed donor and acceptors are also affected by reducing the silanol group concentration. The singlet quenching mechanism changes from predominantly static to increasingly dynamic as the silanol surface concentration is reduced. TNM movement on the surface is indicated by the loss of quenching reaction with decreased sample temperatures. The pyrene triplet excited state is quenched by coadsorbed TNM at lower TNM concentrations than are required for singlet quenching. The dynamic quenching mechanism of the triplet increases significantly using dehydroxylated silica gel. Excited-state quenching occurs by electron transfer on the surface with the formation of the pyrene cation. The strong binding of tetranitromethane to the silica gel surface also changes the photoinduced reaction products. Nitropyrene is formed along with nitroform indicating the reaction mechanism involves charge transfer with pyrene cation formation by a similar mechanism as occurs in acetonitrile.

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Peculiarities of the elementary stages of radiation-induced polymerization of monomers on the surface of solids

Cited by 6 publications

References 2 publications

Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Surface Chemistry Induced by High Energy Radiation in Silica of Small Particle Structures

Quenching of Excited States of Pyrene by Tetranitromethane on SiO₂ Surfaces: Effect of Reaction Temperature, Silica Pore Size, and Surface Silanol Content

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Peculiarities of the elementary stages of radiation-induced polymerization of monomers on the surface of solids

Cited by 6 publications

References 2 publications

Reactions of Electrons on the Surface of γ-Al2O3. A Pulse Radiolytic Study with 0.4 MeV Electrons

Reactions of Electrons on the Surface of γ-Al2O3. A Pulse Radiolytic Study with 0.4 MeV Electrons

Surface Chemistry Induced by High Energy Radiation in Silica of Small Particle Structures

Quenching of Excited States of Pyrene by Tetranitromethane on SiO2 Surfaces: Effect of Reaction Temperature, Silica Pore Size, and Surface Silanol Content

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Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Reactions of Electrons on the Surface of γ-Al₂O₃. A Pulse Radiolytic Study with 0.4 MeV Electrons

Quenching of Excited States of Pyrene by Tetranitromethane on SiO₂ Surfaces: Effect of Reaction Temperature, Silica Pore Size, and Surface Silanol Content