“Super-slow” rotations of spin probes in solid polymers

Лившиц, В. А.; Kuznetsov, V. A.; Barashkova, I. I.; Vasserman, A. M.

doi:10.1016/0032-3950(82)90227-1

Cited by 6 publications

(5 citation statements)

References 6 publications

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“…One of the possible reasons for this discrepancy is the existence of a distribution of molecular mobility in glassy polymers. Assumption of molecular mobility distributions is widely used for interpretation of experimental results for glassy media 5, 6, 9, 11, 12, 15, 17, 19–21, 23, 60–64. In the framework of quasi‐libration model, distribution of molecular mobility is essentially a distribution of quasi‐libration amplitudes of a spin probes.…”

Section: Results Of Spectra Simulationmentioning

confidence: 99%

“…Semiempirical approaches developed for low‐molecular media were used without substantiation in the majority of earlier works concerning polymers. Interpretation of the data obtained in this way for glassy media meets difficulties as the results often contradict the data obtained with other techniques 5–7, 10–12. Two main trends in development of spin probe method have aimed to obtain more precise and reliable data and clearer interpretation.…”

Section: Introductionmentioning

confidence: 99%

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Molecular mobility of nitroxide spin probes in glassy polymers. Quasi‐libration model

Chernova

Vorobiev

2008

J Polym Sci B Polym Phys

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ESR spectra of three spin probes with different molecular volumes: 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl, di-p-anisylnitroxide, and nitroxide derivative of fullerene in glassy polystyrene, polyvinyl trimethylsilane, and Teflon AF-2400 were calculated numerically within the model of quasi-libration motions. Temperature ranges, where the model is capable to reproduce spectra within experimental errors, were defined. It was found that simulation of X-band ESR spectra allows to determine quasi-libration amplitudes around molecular axes X and Y with accuracy $ 3 and around Z axis with accuracy $ 15-20 . A shape of distribution of quasilibration amplitudes was also determined qualitatively by ESR spectra simulations. It was established that the average amplitude of quasi-libration motion depends on the free volume of each polymer and geometrical molecular volume of a spin probe. Quasi-libration amplitudes increase as the temperature increases, and reach the value of 40 degrees. We found that upon further temperature increase, quasi-libration model becomes inapplicable for quantitative numerical spectra simulation.

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Section: Results Of Spectra Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular mobility of nitroxide spin probes in glassy polymers. Quasi‐libration model

Chernova

Vorobiev

2008

J Polym Sci B Polym Phys

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“…The apparent advantage of this correlation approach is the possibility of evaluating the characteristics of molecular mobility directly from ESR spectra. Unfortunately, in the case of glassy polymers, the data obtained with correlation formulas contradict those obtained with other methods 11–16. This is not surprising because these formulas were developed for ESR spectra of nitroxide probes in low‐molecular‐weight media.…”

Section: Introductionmentioning

confidence: 98%

Cyclic loading increases friction and changes cartilage surface integrity in lubricin‐mutant mouse knees

Drewniak

Jay

Fleming

et al. 2012

Arthritis & Rheumatism

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Objective To investigate the effects of lubricin gene dosage and cyclic loading on whole joint coefficient of friction (CoF) and articular cartilage surface integrity in mouse knee joints. Methods Joints from mice with two (Prg4+/+), one (Prg4+/−), and no (Prg4−/−) functioning lubricin alleles were subjected to 26 hours of cyclic loading using a custom-built pendulum. CoF values were measured at multiple time points. Contra-lateral control joints were kept unloaded. Following testing, joints were examined for histological evidence of damage and cell viability. Results At baseline, Prg4−/− CoF values were significantly higher than Prg4+/+ and Prg4+/− values (p<0.001). Cyclic loading continuously increased CoF in Prg4−/− joints. In contrast, Prg4+/− and Prg4+/+ joints had no CoF increases during the first 4 hours of loading. After 26 hours of loading, joints from all genotypes had increased CoF values compared to baseline and unloaded controls. Significantly greater increases occurred in Prg4−/− and Prg4+/− joints compared to Prg4+/+ joints. CoF values were not significantly associated with histological evidence of damage or loss of cell viability. Conclusion Mice lacking lubricin have increased baseline CoF values and are not protected from further increases caused by loading. Prg4+/− mice are indistinguishable from Prg4+/+ mice at baseline, but have significantly greater CoF values following 26 hours of loading. Lubricin dosage affects joint properties during loading, and may have clinical implications in patients for whom injury or illness alters lubricin abundance.

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“…These values are close to the corresponding values determined for SKI 2 using a bulky spin probe. 67 Studies on the kinetics of the formation of nitroxyl radicals in solid elastomers showed that free-radical transformations of double bonds in the presence of nitrogen dioxide differ fundamentally from analogous liquid-phase reactions. 56 The changes in the concentration of nitroxyl radicals as functions of the nitration time of SKI 2 at different concentrations of nitrogen dioxide in the gas phase are shown in Fig.…”

Section: Esr Studies Of the Reactions Of Nitrogen Dioxide With Double...mentioning

confidence: 99%

Reactions of nitrogen oxides with polymers

Pariiskii¹,

Gaponova²,

Davydov³

2000

Russ. Chem. Rev.

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The mechanisms of the reactions of nitrogen oxides and The mechanisms of the reactions of nitrogen oxides and different classes of solid polymers are considered. Particular different classes of solid polymers are considered. Particular emphasis is given to the analysis of the mechanisms of the emphasis is given to the analysis of the mechanisms of the formation of stable nitroxyl radicals. Double bonds and amide formation of stable nitroxyl radicals. Double bonds and amide groups of macromolecules, as well as hydroperoxides and per-groups of macromolecules, as well as hydroperoxides and peroxide macroradicals are shown to be involved in the reactions with oxide macroradicals are shown to be involved in the reactions with nitrogen oxides. The application of nitrogen oxides for the nitrogen oxides. The application of nitrogen oxides for the preparation of spin-labelled polymers and the use of the ESR preparation of spin-labelled polymers and the use of the ESR imaging technique (ESR tomography) for the investigation of the imaging technique (ESR tomography) for the investigation of the structure of the reaction front during nitration of solid polymers structure of the reaction front during nitration of solid polymers are considered. The bibliography includes 111 references are considered. The bibliography includes 111 references. .

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“Super-slow” rotations of spin probes in solid polymers

Cited by 6 publications

References 6 publications

Molecular mobility of nitroxide spin probes in glassy polymers. Quasi‐libration model

Molecular mobility of nitroxide spin probes in glassy polymers. Quasi‐libration model

Cyclic loading increases friction and changes cartilage surface integrity in lubricin‐mutant mouse knees

Reactions of nitrogen oxides with polymers

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