The Effect of Good Solvents on Molecular Motion of Nitroxide Free Radicals in Covalently Labeled Polystyrene and Poly(methyl methacrylate)

Veksli, Zorica; Miller, Wilmer G.

doi:10.1021/ma60057a038

Cited by 57 publications

(23 citation statements)

References 2 publications

(2 reference statements)

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“…[9] confirms the earlier mentioned assumption that the potential-energy barrier of probe rotations should increase with increasing molecular weight of the probe radicals. Since the limiting value of the effective energy of radical rotations, when M w -~ ~, is the same as the activation energy of segmental chain relaxations there should be a correlation between the size of the radical and the size of the polymer segment (21).…”

Section: Discussionsupporting

confidence: 90%

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Rotations of nitroxide radicals in condensed polymeric systems

Weber

Törmälä

1978

Colloid Polymer Sci

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Section: Discussionsupporting

confidence: 90%

“…in polymeric solids and melts. It could be shown that motional data of these radicals can give information about melting (primary) transition (1-3), glass (secondary) transition (4)(5)(6)(7)(8), local short range main chain relaxations (1, 7) and local side chain relaxations (9).…”

Section: Introductionmentioning

confidence: 99%

Rotations of nitroxide radicals in condensed polymeric systems

Weber

Törmälä

1978

Colloid Polymer Sci

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“…The relaxation of the nitroxide is facilitated by backbone motions extending only a few atoms from the point of attachment, i.e., to local mode motions, as deduced from mole cular weight and other studies by several investigators (26,27). Thus in an adsorbed molecule an isolated loop or tail extending into the solvent should give a motionally narrowed three line spectrum if the loop or tail is greater than a minimum size (probably four-to-six bonds about which rotation can occur).…”

mentioning

confidence: 99%

Conformation and Mobility of Polymers Adsorbed on Oxide Surfaces by ESR Spectroscopy

Liang

Dickenson

Miller

1980

ACS Symposium Series

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“…1 Many authors have studied molecular motion of poly(methyl metacrylate) (PMMA) by the spin-label method. Veksli et al, 2 Bullock et al, 3 Shiotani et al, 4 and Tsay et al 5 have analyzed the observed spectra based on the assumption that the rotational motion relies upon the simplified expression of correlation time, ' R proposed by Freed et al 6 for isotropic rotation in the slowmotional region and Kivelson 7 for isotropic rotation in the motional narrowing region.…”

mentioning

confidence: 99%

Spin Label Study of the Factors Affecting Molecular Motion of Poly(methyl methacrylate)

Shimada

Kashima

1996

Polym J

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ABSTRACT:The electron spin resonance (ESR) line shape ofnitroxide radical labels attached to poly(methyl methacrylate) (PMMA) chains was studied as a function of temperature. In order to clarify various factors affecting molecular motions of PMMA chains, molecular mobility ofa spin-labeled PMMA chain (L-chain) in another PMMA (M-chain) matrix was estimated by the ESR method. Isotactic and atactic PMMA having narrow molecular weight distribution were used as L-and M-chains. Strong dependencies of molecular mobility on molecular weights (ML and MM) of the chains and tacticity of M-chains were found. For example, the transition temperature, T500 at which the extrema separation width due to anisotropic hyperfine splitting drops sharply increases with increasing molecular weight of M-chains. The correlation times at the transition temperatures, calculated from the ESR spectra are compared with those in so-called relaxation map and the nitroxide rotational motion is concluded to strongly correlate with micro-Brownian motion of the PMMA chains. It was also found that the correlation times estimated by the ESR method is proportional to ML 0 · 5 and MM when MM<2M, and independent of MM when MM>2M,. Here, M, is the molecular M, weight between entanglements. These experimental facts are reflected on Stokes-Einstein and reptation types of diffusions of L-chains.KEY WORDS Electron Spin Resonance / Spin Label / Molecular Motion / Poly(methyl metacrylate) Relaxation Map / Distribution of Correlation Time / It has been well established that spin-label technique is very useful to characterize molecular motion in solid polymers. ESR method is a simple and effective way of determining molecular mobility on a time scale of -10-9 s. We developed spin-label technique to investigate the structure and dynamics behavior of polymer chain at a particular site in a complicate system such as polymer blends. 1 Many authors have studied molecular motion of poly(methyl metacrylate) (PMMA) by the spin-label method. Veksli et al.,2 Bullock et al.,3 Shiotani et al.,4 and Tsay et al. 5 have analyzed the observed spectra based on the assumption that the rotational motion relies upon the simplified expression of correlation time, ' R proposed by Freed et al. 6 for isotropic rotation in the slowmotional region and Kivelson 7 for isotropic rotation in the motional narrowing region.On the other hand, Shiotani et al. 8 concluded the anisotropic rotation of the side chain from the detailed analysis of the ESR spectrum of the spin-labeled PMMA. Murakami et al. 9 and Tsay et al. 10 presented spectral evidence to indicate that the double-peak feature of ESR spectrum observed for the spin-labeled PMMA can be explained satisfactorily on the basis of free-volume present in the glassy state. Cameron et al. 11 also interpreted the double-peak feature of the ESR spectrum of a nitroxide spin probe as reflecting from a distribution of correlation time arising from a distribution of freevolume within a polymer matrix. On the other hand, the correlation time of the...

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The Effect of Good Solvents on Molecular Motion of Nitroxide Free Radicals in Covalently Labeled Polystyrene and Poly(methyl methacrylate)

Cited by 57 publications

References 2 publications

Rotations of nitroxide radicals in condensed polymeric systems

Rotations of nitroxide radicals in condensed polymeric systems

Conformation and Mobility of Polymers Adsorbed on Oxide Surfaces by ESR Spectroscopy

Spin Label Study of the Factors Affecting Molecular Motion of Poly(methyl methacrylate)

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