Hyperfine Structure in the OD ESR Spectra of Recombining Charge Pairs in Doped Polyethylene Matrices

Verkhovlyuk, V. N.; Borovkov, V. I.; Bagryansky, V. A.; Zikirin, Samat B.; Taratayko, Andrey I.; Анисимов, О. А.; Molin, Yu. N.

doi:10.1007/s00723-018-0978-1

Cited by 3 publications

(7 citation statements)

References 29 publications

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“…77,78 This estimation suggests that charge carriers involved in recombination on a longer time scale are radical ions of the aromatic solute, that is para-terphenyl-d 14 . Note that this is also consistent with the results reported by Verkhovlyuk et al 56 In those experiments, optically detected EPR spectra obtained in polyethylene doped with aromatic molecules were just a superposition of the spectra of both radical cations and radical anions of the dopants.…”

Section: Resultssupporting

confidence: 92%

“…As the luminophore we used perdeuterated para- terphenyl -d 14 ( p TP, 98%, Aldrich) and 4,4′′-bis[1-decyloxy)ethyl]-1,1′:4,1′′-terphenyl (bDOTP, synthesized as described previously). For PE35, PE4, PELD, PPa, and P4M1P, p TP was introduced by different methods, that is, either by melting in the absence of oxygen or by dissolving in alkanes or tetrahydrofuran under heating.…”

Section: Methodsmentioning

confidence: 99%

“…As shown in a recent work, in the case of doped polyethylene and polypropylene, OD EPR allows observation of the hyperfine structure in the EPR spectra of the secondary radical ions formed via the capture of the primary charge carriers by luminophore molecules at room or elevated temperature. In that work, it was demonstrated that for successful observation of the OD EPR spectrum, the diffusion of charge carriers should be sufficiently effective, and the increase in temperature facilitates the observation.…”

Section: Introductionmentioning

confidence: 98%

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Radiation-Induced Fluorescence from Doped Polyolefins on a Nanosecond Time Scale: Kinetics of the Processes Involving Geminate Radical Ions

2019

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The delayed radiation-induced fluorescence from polyethylene and its alkyl-and fluorine-substituted analogues doped with aromatic luminophores was studied in the time range of 1−1000 ns. Qualitative analysis of the effects of a magnetic field on the fluorescence decay indicated that, in all polyolefins studied, the main portion of the fluorescence observed arose from the recombination of geminate spincorrelated radical ion pairs (RIPs). In the case of polyethylene, this conclusion was supported by observing the effect of an external electric field on the fluorescence decay. It was shown by comparison with the computer simulation of intratrack recombination that the tunneling character of the RIP recombination, which had an asymptotic time dependence of the geminate recombination rate close to t −1 , was typical of most studied polyolefins at temperatures below 273 K in the time range studied. The increase to room temperature and above caused a gradual transition to a regime where the geminate recombination rate was mainly determined by the migration of RIP partners with time dependence close to t −3/2 . The low estimate of the electron transfer distance upon the ion recombination in this regime was about 2 nm. In polyethylenes, exposed to an irradiation of 0.3−0.4 MGy, the role of charge carrier diffusion became hardly noticeable because of the cross-linking of polyethylene chains and the increase in polymer matrix stiffness. Oxygen, dissolved in a polymer doped with aromatic molecules, caused quenching of the recombination luminescence due to electron transfer from the dopant radical anion to the oxygen molecules. At room temperature, typical distances for such electron transfer were estimated to be ∼1.5 nm.

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Section: Resultssupporting

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Radiation-Induced Fluorescence from Doped Polyolefins on a Nanosecond Time Scale: Kinetics of the Processes Involving Geminate Radical Ions

2019

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“…Haloalkanes were stored over molecular sieves of 4 Å. 4,4″-Bis[1-(decyloxy)ethyl]-1,1′:4,1″-terphenyl (bDOTP), synthesized as described previously, 21 was provided by A. Taratayko. Prior to experiments, oxygen was removed from the solutions containing the studied substances using several "freeze−pump−thaw" cycles.…”

Section: Methodsmentioning

confidence: 99%

Spin-Correlated Radical Ion Pairs Generated in Liquid Haloalkanes Using High-Energy Radiation

Borovkov

2018

J. Phys. Chem. B

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The probability of formation of spin-correlated secondary radical ion pairs (RIPs) in diluted solutions of charge acceptors in irradiated haloalkanes is believed to be extremely low due to the dissociative attachment of excess electrons to solvent molecules. Contrary to this, it has been found that spin-correlated RIPs can be formed upon irradiation in some liquid chloroalkanes with yield sufficient to observe the recombination fluorescence of the RIP's partners. This allowed the study of primary radical cations (RCs) as well as radical ionic states of molecules dissolved in haloalkanes using the method of time-resolved magnetic field effect (TR MFE) in radiation-induced fluorescence. With this method, the magnetic resonance characteristics of the solvent RCs in a series of liquid haloalkanes were examined for the first time. For the 1,2-dichloroethane RC, the rate of scavenging by solute molecules and the dominant mechanisms of paramagnetic relaxation were determined. Polysulfone and poly(ethyl methacrylate) were used to demonstrate that due to their high dissolving ability, chloroalkanes can be exploited as solvents to study the magnetic resonance characteristics of radical ionic states of polymeric molecules in solutions with the TR MFE method.

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“…This result implies comparatively rapid large-amplitude librations or rotation of the radical ions in the PVC matrix under the experimental conditions. Note that the EPR spectra of secondary radical ions of aromatic compounds observed in a polyethylene matrix also did not exhibit noticeable anisotropic broadening. Naturally, the decrease in the initial slope of the TR MFE curves that takes place upon doping with p- TP- d 14 is determined by the decrease in the hyperfine coupling (HFC) constants of the radical ions of the perdeuterated compound.…”

mentioning

confidence: 92%

Probing an Isolated Conjugated Polymer Molecule with Radiation-Generated Spin-Correlated Polaron Pairs

Borovkov

2021

J. Phys. Chem. Lett.

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An understanding of the interplay between the spin and electronic degrees of freedom of polarons migrating along conjugated polymer molecules is required to further the development of organic electronics and spintronics. In this study, a novel experimental approach is proposed for studying spin-correlated polaron pairs (PPs) on an isolated molecule of a conjugated polymer. The polymer molecule of interest is immobilized in a nonluminescent poly(vinyl chloride) matrix, which is irradiated with X-rays to rapidly form secondary PPs on the conjugated polymer. The migration, recombination, and evolution of the spin state of the PPs can be monitored at nanosecond resolution by observing the recombination fluorescence under different magnetic fields. Examples supporting this concept are presented.

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Hyperfine Structure in the OD ESR Spectra of Recombining Charge Pairs in Doped Polyethylene Matrices

Cited by 3 publications

References 29 publications

Radiation-Induced Fluorescence from Doped Polyolefins on a Nanosecond Time Scale: Kinetics of the Processes Involving Geminate Radical Ions

Radiation-Induced Fluorescence from Doped Polyolefins on a Nanosecond Time Scale: Kinetics of the Processes Involving Geminate Radical Ions

Spin-Correlated Radical Ion Pairs Generated in Liquid Haloalkanes Using High-Energy Radiation

Probing an Isolated Conjugated Polymer Molecule with Radiation-Generated Spin-Correlated Polaron Pairs

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