Rotational mobility of guest molecules studied by method of oriented spin probe

Vorobiev, Andrey Kh.; Gurman, V.S.; Klimenko, T. A.

doi:10.1039/a908429k

Cited by 31 publications

(40 citation statements)

References 13 publications

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“…Experimental spectra in the corresponding temperature range are satisfactorily described by a quasi-librational model. 15,17 Apparently, the motion of a probe is restricted by the cage walls. As the temperature becomes higher, the mobility of the polymer fragments forming the cage increases, and the cage starts to rearrange and reorient.…”

Section: Resultsmentioning

confidence: 99%

“…More detailed and exact data can be obtained by the numerical simulation of ESR spectra and by the comparison of the calculated and experimental spectra. 12,15,[17][18][19] However, in the case of glassy polymers, quantitative numerical simulations often fail to reproduce the experimental spectra quantitatively. Thus, information obtained by the spin-probe method for glassy polymer media remains insufficiently reliable.…”

Section: Introductionmentioning

confidence: 99%

“…This type of motion in glasses has been evidenced by highfrequency ESR, 21 magnetization transfer, 22 and spinecho experiments. [23][24][25][26] The simulation of ESR spectra 15,17 has shown that amplitudes of quasi-librations increase and the distribution of quasi-libration amplitudes becomes apparent as the temperature rises within temperature range I.…”

Section: Introductionmentioning

confidence: 99%

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Molecular mobility of nitroxide spin probes in glassy polymers: Models of the complex motion of spin probes

Chernova

Vorobiev

2011

J of Applied Polymer Sci

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The rotational mobility of molecules in glassy polymers was investigated by quantitative simulations of electron spin resonance spectra of nitroxide spin probes with molecules of different sizes. The motional models were determined unambiguously when the experimental and calculated spectra coincided within the level of experimental error. Temperature ranges in which different motional models were applicable were determined. Quasilibrational movements and the distribution of rotational mobility were found to be necessary for the qualitative description of spin-probe mobility in glassy polymers. The quantitative and empirical characteristics of rotational mobility were examined.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Molecular mobility of nitroxide spin probes in glassy polymers: Models of the complex motion of spin probes

Chernova

Vorobiev

2011

J of Applied Polymer Sci

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“…Molecular motions in glassy supercooled liquids have been studied using dielectric relaxation [1][2][3][4], nuclear magnetic resonance (NMR) [4][5][6][7], electron paramagnetic resonance (EPR) [8][9][10][11], and many other techniques. However, the microscopic nature of the phenomenon of glass transition is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy

Isaev

Кулик

Kirilyuk

et al. 2010

Journal of Non-Crystalline Solids

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“…In our opinion, the models of unrestricted orientational motions such as Brownian diffusion (including uniaxial diffusion) of jump rotations may be certainly ruled out on the basis of the data available in literature. Experiments with a light-oriented spin probe did not show a change of the orientation of a probe at the temperatures where the temperature dependence of EPR line shape is observed [34]. Single molecule studies of fluorescent probe molecule [35] show that near Tg unrestricted motion occurs only at the second time scale which is many orders of magnitude larger than the time scale when motion manifests itself in EPR (~ 10 -7 S).…”

Section: Resultsmentioning

confidence: 88%

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

2006

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Continuous-wave electron paramagnetic resonance (CW EPR), echo-detected (ED) EPR, and field-step electron-electron double resonance (FS ELDOR) were simultaneously applied to study molecular motions of nitroxide spin probes of two different types in glassy o-terphenyl. A strong linear temperature dependence of the overall splitting of the CW EPR lineshape was found for nitroxide Tempone and only a weak one fora phenyl-ring-containing imidasoline nitroxide. The linear temperature dependence of the splitting is explained within the model of harmonic librations.The assessed libration frequency for Tempone is of the order of 3 9 IO n rad/s. The observed remarkable difference between the two nitroxides is explained by the different strength of interactions between guest and host molecules and by dynamical heterogeneity of the glass. The nonlinear temperature dependence above 250 K is attributed to the onset of anharmonic motion that is postulated in a number of neutron scattering and M6ssbauer spectroscopy studies for molecular glasses and proteins (the so-called dynamical transition). Above 245 K also ED EPR spectra change drastically, which may be explained on the same ground. Magnetization transfer was observed in FS ELDOR for nitroxide Tempone, with a time constant around 10 -5 s. Ir was found to be almost temperatureindependent between 160 K and 265 K and was attributed to the Johari-Goldstein 13-relaxation process. For the phenyl-ring-containing imidasoline nitroxide this transfer was not observed, which may be explained again by the dynamical heterogeneity of the glass and by small effectivity of the 13-relaxation process in this case.

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Rotational mobility of guest molecules studied by method of oriented spin probe

Cited by 31 publications

References 13 publications

Molecular mobility of nitroxide spin probes in glassy polymers: Models of the complex motion of spin probes

Molecular mobility of nitroxide spin probes in glassy polymers: Models of the complex motion of spin probes

Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides ino-terphenyl glass: Dynamical transition, dynamical heterogeneity and β-relaxation

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