Molecular motion in glassy polystyrenes

Schaefer, Jacob; Sefcik, M. D.; Stejskal, E. O.; McKay, Robert A.; Dixon, William J.; Cais, R. E.

doi:10.1021/ma00136a001

Cited by 135 publications

(112 citation statements)

References 17 publications

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“…Apparently, the influence of glass beads is mainly confined to motions with frequencies well above ~ 104 Hz. This could very well be motions of the 'first type' as described by Schaefer et al 28. Herein Table 3 The three '3C n.m. low-•quency ring motions are coupled to main-chain reorientations, i.e.…”

Section: Solid-state Nmrsupporting

confidence: 54%

Particle size dependence of the Young's modulus of filled polymers: 2. Annealing and solid-state nuclear magnetic resonance experiments

Vollenberg

Haan

Ven

et al. 1989

Polymer

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Section: Solid-state Nmrsupporting

confidence: 54%

Particle size dependence of the Young's modulus of filled polymers: 2. Annealing and solid-state nuclear magnetic resonance experiments

Vollenberg

Haan

Ven

et al. 1989

Polymer

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“…We assumed an isotropic high-frequency 1801 flip motion for the benzene ring, which is combined with the overall main-chain rotational reorientation motion. 11 It is necessary to consider both the side-chain and main-chain motions for accurate estimation of the molecular motion. However, at higher temperatures, SBR performs like a liquid under higher frequency motion, so that we were not able to distinguish both motions from the temperature dependence of T 1 H alone.…”

Section: Temperature Dependence Of T 1 Hmentioning

confidence: 99%

Influence of magic angle spinning on T1H of SBR studied by solid state 1H NMR

Asano

Hori

Kitamura

et al. 2012

Polym J

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We have investigated the influence of the high centrifugal pressure caused by fast magic-angle spinning (MAS) on the molecular motion of styrene-butadiene rubbers (SBR) filled with SiO 2 (SBR/Si composite) though solid-state magic-angle spinning nuclear magnetic Resonance ( 1 H MAS NMR) measurements. Because the 1 H-1 H dipolar interaction of elastomers is weak compared with that of glassy polymers, a narrower 1 H linewidth is observed under fast MAS. The temperature dependence of the 1 H spin-lattice relaxation time (T 1 H ) revealed that the T 1 H minimum increases with the MAS rate. Furthermore, we observed a difference in the temperature dependence of T 1 H between end-chain-modified SBR and normal (unmodified) SBR in the SBR/Si composites. The temperature dependence of T 1 H is described by the Bloembergen-Purcell-Pound theory, with the assumption that the correlation time obeys the Williams-Landel-Ferry empirical theory. The fitting showed that the molecular motion does not change significantly until a MAS rate of 20 kHz, with the motional mode changing considerably at a MAS rate of 25 kHz. The motion of SBR in the unmodified SBR/Si composite was greatly affected by the fast MAS rates. Furthermore, the plot of the estimated centrifugal pressure versus the T 1 H minimum resembled the stress-strain curve. This result enables the detection of macroscopic physical deformation by the microscopic parameter INTRODUCTIONSolid-state NMR is useful for the investigation of the molecular motion of the functional groups of elastomers and polymers. In particular, the recent development of the magic-angle spinning (MAS) technique allows a sample rotor to be spun much faster than 20 kHz. Thus, we can detect the high-resolution 1 H signals of rubbers and elastomers under the fast rates that are possible in MAS because these fast MAS rates effectively reduce the signal broadening that arises from the relatively weak 1 H-1 H dipolar interaction of elastomers (in comparison with that of glassy solid polymers).Generally, spin-lattice relaxation time (T 1 ) is observed to study molecular motion. In the case of rare spins such as 13 C, however, it is time-consuming to observe the signals and measure an accurate T 1 with a good signal-to-noise ratio. In contrast, proton signals are intense enough to allow quick analysis of molecular motion through the T 1 measurement. However, for a glassy solid polymer, the strong 1 H-1 H dipolar interaction obscures the individual functional group signals, even with fast MAS. For rubbers and elastomers under fast MAS, in contrast, each peak assigned to a respective functional group can be detected because of the weak 1 H-1 H dipolar interaction. Furthermore, it is easy to detect 1 H-T 1 ( 1 H spin-lattice relaxation time (T 1 H )) accurately. In contrast, it is well known that MAS causes the temperature of the inner sample to increase because of friction between the MAS and the air. In addition, it has recently been reported that fast MAS causes

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“…Magnetic resonance experiments often generate data that are modeled as a sum of exponentials (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Experiments relying on NMR to probe reaction kinetics, diffusion, molecular dynamics, and xenobiotic metabolism are only some of the applications where parameter estimates from exponential models provide insight into chemical and biological processes.…”

Section: Introductionmentioning

confidence: 99%

Exponential parameter estimation (in NMR) using Bayesian probability theory

Bretthorst

Hutton

Garbow

et al. 2005

Concepts Magn. Reson.

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Data modeled as sums of exponentials arise in many areas of science and are common in NMR. However, exponential parameter estimation is fundamentally a difficult problem. In this article, Bayesian probability theory is used to obtain optimal exponential parameter estimates. The calculations are implemented using Markov chain Monte Carlo with simulated annealing to draw samples from the joint posterior probability for all of the parameters appearing in the exponential model. Monte Carlo integration is then used to approximate the marginal posterior probabilities for each of the parameters. We give numerical examples taken from simulated data and NMR relaxation experiments to illustrate the calculations and the effect of prior information on the parameter estimates.

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Molecular motion in glassy polystyrenes

Cited by 135 publications

References 17 publications

Particle size dependence of the Young's modulus of filled polymers: 2. Annealing and solid-state nuclear magnetic resonance experiments

Particle size dependence of the Young's modulus of filled polymers: 2. Annealing and solid-state nuclear magnetic resonance experiments

Influence of magic angle spinning on T1H of SBR studied by solid state 1H NMR

Exponential parameter estimation (in NMR) using Bayesian probability theory

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