Chain fluctuations in the amorphous regions of polyethylene as indicated in proton relaxation spectroscopy

Voigt, G.; Kimmich, Rainer

doi:10.1016/0032-3861(80)90029-4

Cited by 35 publications

(45 citation statements)

References 31 publications

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“…By the aid of oxygen-enhancement of the spin lattice relaxation it was found that the dominating amorphous parts o~ partially crystalline polyethylene are homogeneous with respect to fluctuations [7]. This virtually agrees with the conclusions drawn from deuterium lineshapes [22].…”

Section: Technical Details and Sample Characterizationsupporting

confidence: 68%

“…The most elementary one is the y-process. Figure 2 shows the corresponding proton Tl-dispersion [7] found by field-cycling relaxation spectroscopy. (At these temperatures proton spinlattice relaxation is dominated by the amorphous regions [7], [39]).…”

Section: Y-process Of Amorphous Polyethylenementioning

confidence: 99%

“…The fiel&cycling relaxation spectrometer has been described elsewhere [7]. The high-frequency (v > 20 MHz) T l-and T2-data have been recorded with a conventional Bruker SXP 4-100 pulse spectrometer using the usual pulse and echo sequences.…”

Section: Technical Details and Sample Characterizationmentioning

confidence: 99%

“…The broken line for the yprocess has been calculated with the complete expression for defect diffusion limited by reflecting barriers [40]. At these tempe~'atures neither methyl group rotation [7] nor motions in the crystallites [7], [39], have any influence on the proton T~-dispersion, which hence is governed by the "amorphous '' methylene groups. The homogeneity of the relaxation within the amorphous parts is discussed in reference [7].…”

Section: Y-process Of Amorphous Polyethylenementioning

confidence: 99%

“…Crucial processes frequently assumed are defect diffusion [5]- [7] and reptation [2], [8], [9]. The aim of this work is to verify these special fluctuations and to derive a unified concept in the sense of a hierarchy of primary and secondary motions.…”

Section: Introductionmentioning

confidence: 99%

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NMR field-cycling relaxation spectroscopy, transverse NMR relaxation, self-diffusion and zero-shear viscosity: Defect diffusion and reptation in non-glassy amorphous polymers

Kimmich

Bachus

1982

Colloid & Polymer Sci

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Molecular weight and frequency dependences, respectively, of the nuclear magnetic relaxation times and the self-diffusion coefficient of polyethylene and polystyrene have been investigated over several orders of magnitude. The relation to viscous behaviour is established. A closed concept is developed. Conclusions are: a) The y-process in amorphous polyethylene can be described by the aid of the limited defect diffusion model. b) The fl-process in the same material is interpreted as limited reptation. The intensity function of this process depends on the amorphous content. c) The three-component description of chain fluctuations already presented in previous papers has been modified in order to account for the precise molecular weight dependences, which now have been measured. Especially we distinguish between internal and whole-chain reptation. A correlation function is derived, which predicts the right limiting behaviour inspite of its semi-empirical character. The three components can be identified by the frequency and molecular weight dependences of the nuclear magnetic relaxation times. d) The molecular weight dependences are subdivided by 3 (spin lattice relaxation), 2 (transverse relaxation), 1 (zero-shear viscosity) and 0 (self-diffusion coefficient) characteristic molecular weights (Me, MBo MA~ ). All of them can be derived as dynamic case transitions. Especially the classical critical molecular weight of the viscosity can be explained by the transition between tube fluctuations governed by internal and wholechain reptation, respectively. The assumption of a structural transition is unnecessary. e) A semi-empirical expression for the zero-shear viscosity is derived for the whole range of chain lengths. The analysis of the molecular weight dependences of the NMR relaxation times straightforwardly leads to those of the zero-shear viscosity. f) Using a NMR field-gradient method, it is shown again that the self-diffusion coefficients of both melt examples obey D ~ M~72~ g) Matrix effects predominantly are due to changes in the free volume.

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Section: Technical Details and Sample Characterizationsupporting

confidence: 68%