Selectivity and efficiency of pyrene attachment to alkanes induced by broadband X-rays

Brown, Gerald O.; Guardala, Noel A.; Price, J. L.; Weiss, Richard G.

doi:10.1590/s0001-37652003000100005

Cited by 2 publications

(7 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have demonstrated that it is possible to attain selective and efficient attachment of pyrene to polyethylene chains in films using <4.1 eV (>300 nm) photons, as well as megaelectronvolt-range protons . The nature of the major attachment species in the films, a 1-pyrenyl group, is supported by results from UV/vis and 〈1.3〉 MeV X-ray irradiations 5c of pyrene-doped matrixes of solid saturated hydrocarbons.…”

Section: Introductionmentioning

confidence: 72%

“…The shapes of the emission spectra at λ ex = 343 nm change from being like that of 1-ethylpyrene at the lower doses to one with a broad underlying band centered at ca. 470 nm, attributed primarily to an “interchain” excimer, at the highest dose. The longest fluorescence temporal decay constant, τ 1 , is very similar in magnitude to that of 1-ethylpyrene and is attributed to singly attached pyrenyl units within the polyethylene matrix.…”

Section: Resultsmentioning

confidence: 99%

“…When the wavelength was increased to >240 nm (<5.1 eV), only photoproducts with one cyclohexane per pyrene molecule were detected, but each attachment requires absorption of two photons . In addition, upon exposure to broadband 〈1.3〉 MeV X-rays, pyrene in solid orthorhombic heneicosane (C 21 H 44 ) yields mono- and disubstituted products, but pyrene in liquid cyclohexane yields products with only one solvent molecule attached 5c…”

Section: Resultsmentioning

confidence: 99%

“…The nature of the major attachment species in the films, a 1-pyrenyl group, is supported by results from UV/vis and 〈1.3〉 MeV X-ray irradiations 5c of pyrene-doped matrixes of solid saturated hydrocarbons. Within the 1.0−4.5 MeV range of protons studied, selectivity of attachment of pyrene to polymer chains was independent of proton kinetic energy but decreased with increasing proton dose . The efficiency of attachment increased somewhat with decreasing polymer crystallinity, and a dependence on crystallinity that could be ascribed to other factors as well was present.…”

Section: Introductionmentioning

confidence: 86%

“…The results are compared internally and with those from irradiations by UV/vis (electronvolt-range) photons to determine the degree to which the mechanisms of attachment are dependent on the source of the deposited energy. In addition, we show that stacks of pyrene-doped polyethylene films provide a histogram of energy deposition by ionizing radiation: individual films within the stacks contain information about particle kinetic energy (via depth of penetration) and dose (via concentrations of attached 1-pyrenyl groups); the particles leave a history of their number and energy within the films.…”

Section: Introductionmentioning

confidence: 98%

See 4 more Smart Citations

Comparison of Energy Deposition Modes in Polyethylene Films by Megaelectronvolt Range Neutrons, Electrons, Protons, and α Particles as Monitored by Covalent Attachment of Doped Pyrene Molecules

Brown¹,

Guardala²,

Price³

et al. 2003

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

The selectivity and efficiency of the covalent attachment of pyrene molecules to chains of polyethylene (PE) films by various forms of ionizing radiation (neutrons, electrons, protons, and α particles) have been examined while varying several aspects of the reactions. The results are compared with those from irradiations by >300 nm (<4.1 eV) photons. For each type of ionizing radiation, selectivity and attachment efficiency (G) increase with decreasing particle dose. Bombardment by protons, α particles, and electrons produces significant amounts of pyrene molecules attached at two positions, whereas comparable doses of >300 nm (<4.1 eV) photons yield monosubstituted pyrenes only. Higher doses of photons result in attached species that are not pyrenyl in nature. Selectivity is independent of particle kinetic energy in the 3.0−7.0 MeV range for α particles and in the 1.0−4.5 MeV range for protons. Bombardment by 〈2.0〉 MeV neutrons is the least efficient of the ionizing radiation sources explored. Selectivity of attachment is independent of PE crystallinity and so is efficiency when protons or α particles are the radiation source. Significant cross-linking and scission of PE chains accompanies the bombardments at higher doses. The nature of the transformation of particle kinetic energy to potential energy and eventually to work as a function of depth of penetration is explored by analyzing individual pyrene-doped PE films that were bombarded in stacks. They indicate that both the selectivity and efficiency of attachment correlate in different ways with the linear transfer of energy to a film. Where direct comparisons are possible, the differing forms of ionizing radiation appear to interact with the polymer matrixes in a somewhat similar manner. However, there are important, subtle differences as well and they are indicated.

show abstract

Section: Introductionmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations