Carbon-13 (T<sub>1p</sub>) Experiments on Solid Glassy Polymers

Schaefer, Jocob; Stejskal, E. O.; Steger, Theodore R.; Sefcik, M. D.; McKay, Robert A.

doi:10.1021/ma60077a018

Cited by 109 publications

(81 citation statements)

References 9 publications

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“…By spin alignment measurements we could prove, in fact, that the C-CH 3 bond direction must be fixed on a timescale of at least 50 ms at 380 K, this limit -againbeing due to spin-lattice relaxation. The macromolecular chains must, therefore, be essentially interlocked in the glassy state [76]. We do not find small angle fluctuations as recently discussed by Schaefer et al [77], employing magic angle spinning ~3C NMR at room temperature, making use of 13C-1H dipolar coupling.…”

Section: Molecular Motion In Polycarbonatesupporting

confidence: 58%

Molecular dynamics of solid polymers as revealed by deuteron NMR

Spiess

1983

Colloid & Polymer Sci

467

293

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Pulsed deuteron NMR spectroscopy is described, which has recently been developed to become a powerful toot for studying molecular dynamics in solid polymers. It is shown that by analyzing the line shapes of 2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. By applying these techniques to selectively deuterated polymers, motional mechanisms involving different segments of the monomer unit can be monitored. In addition, motional heterogeneities in glassy polymers can be detected. The information about polymer dynamics available now is illustrated by a number of experimental examples. The chain motion in the amorphous regions of linear polyethylene is discussed in detail and it is shown that it can clearly be distinguished from the chain motion of an amorphous polymer above the glass transition, where polystyrene is used as an example. Localized motions in the glassy state are illustrated through the jump motion phenyl groups exhibit both in the main chain (polycarbonate) and as a side group (polystyrene). The latter polymers also serve as examples for detecting motional heterogeneity. Finally, the mobility in novel classes of systems, liquid crystalline polymers and polymer model membranes as revealed by 2H NMR are described.

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Section: Molecular Motion In Polycarbonatesupporting

confidence: 58%

Molecular dynamics of solid polymers as revealed by deuteron NMR

Spiess

1983

Colloid & Polymer Sci

467

293

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“…As a result of this there may be contributions from transverse relaxation effects as well as spin-lattice effects. 19 For a truly rigid system it would be expected that the size of this effect would depend on the number of attached protons.…”

Section: Solid State Nmr Spectroscopymentioning

confidence: 99%

Solid state NMR, IR and X-ray diffraction studies of the structure and motion of L-leucinamide

Wang¹,

Belton²,

Tang³

et al. 1997

J. Chem. Soc., Perkin Trans. 2

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Crystalline L-leucinamide has been studied by 13 C CP/MAS NMR, FTIR spectroscopy and X-ray crystallography. The 13 C CP/MAS spectrum of crystalline L-leucinamide has been assigned using the depolarisation-repolarisation method. Two magnetically non-equivalent molecules in the unit cell have been found from the 13 C CP/MAS spectra. Non-equivalence is also observed in the FTIR spectrum. The molecular dynamics were studied by measuring 13 C spin-lattice relaxation in both laboratory and rotating frames. Results show that the mobilities of the two molecules are very different. Spin-lattice relaxation times for the two carbons differ by an order of magnitude. Determination of the crystal structure by Xray crystallography confirmed the existence of two distinct molecules in the unit cell; these differed in the orientation of the amide groups and in their involvement in the hydrogen bonding scheme, which may account for the observed NMR behaviour.

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“…Therefore was focussed our attention on the phenylene motion which has not been so far defined [1,2,6]. The repeat unit of polycarbonate, selectively deuterated at the phenylene ring (henceforth denoted by PC 4) is depicted in Figure 1.2H NMR line shape studies of the methyl groups are reported elsewhere [5].…”

Section: Introductionmentioning

confidence: 99%

Phenylene motion in polycarbonate and polycarbonate/additive mixtures

Wehrle

Hellmann

Spiess

1987

Colloid & Polymer Sci

133

102

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Pulsed deuteron NMR line shapes have been analysed to characterize type and time scale of the phenylene group motion in glassy bisphenol-A polycarbonate. The motional mechanism involves ~z-flips about the CIC4 axis augmented by small angle fulctuations about the same axis, reaching arms amplitude of _+ 35 ~ at 380 K. The distribution of correlation times for the n-flips is heterogeneous in nature and can be described either by a log-Gaussian or an asymmetric distribution with a more rapid decay at high correlation times comparable to the Williams-Watts distribution. From both distributions essentailly the same mean activation energy of 37 kJ/mol is obtained, whereas the temperature dependent width of the highly asymmetric distribution is somewhat smaller compared to the log-Gaussian distribution. Time scale and activation energy of the n-flip motion are correlated to secondary mechanical relaxations. Low molecular mass additives, which suppress the mechanical relaxation, also hinder the phenylene motion for a substantial fraction of phenylene groups. The effect of additives is not only to shift the mean value of the distribution of correlation times to higher values but also to increase drastically the width of the distribution. The results of this work strongly suggest that the secondary mechanical relaxation and the large amplitude motions of the phenylene groups in polycarbonate are related.

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Carbon-13 (T_1p) Experiments on Solid Glassy Polymers

Cited by 109 publications

References 9 publications

Molecular dynamics of solid polymers as revealed by deuteron NMR

Molecular dynamics of solid polymers as revealed by deuteron NMR

Solid state NMR, IR and X-ray diffraction studies of the structure and motion of L-leucinamide

Phenylene motion in polycarbonate and polycarbonate/additive mixtures

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Carbon-13 (T1p) Experiments on Solid Glassy Polymers

Cited by 109 publications

References 9 publications

Molecular dynamics of solid polymers as revealed by deuteron NMR

Molecular dynamics of solid polymers as revealed by deuteron NMR

Solid state NMR, IR and X-ray diffraction studies of the structure and motion of L-leucinamide

Phenylene motion in polycarbonate and polycarbonate/additive mixtures

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Product

Resources

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Carbon-13 (T_1p) Experiments on Solid Glassy Polymers