Dielectric Relaxation in Liquid Polypropylene Oxides

Baur, M. E.; Stockmayer, W. H.

doi:10.1063/1.1696691

Cited by 168 publications

(103 citation statements)

References 33 publications

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“…A large peak at some frequency w, is accompanied by a small one at position w,, where the latter frequency is several orders of magnitude smaller than the former (Baur and Stockmayer 1965, Alper el a1 1976, Johari 1986, Fu e f a1 1991).…”

Section: Examples For A-relaxation Susceptibilitiesmentioning

confidence: 99%

Comments on the alpha -peak shapes for relaxation in supercooled liquids

Fuchs

Götze

Hofacker

et al. 1991

J. Phys.: Condens. Matter

145

152

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Abstract. The e-peak m t e r functions hs obtained within the mode coupling theory for the supercooled liquid dynamics near the 91-transition singularity are discussed. Double peak phenomena are found 84 a generic feature of the theory related to the self crossing of the transition hypersurface. They lead to two scenarios for liquid to glass transitions characterized by e'-e-peak pairs and by o -" x e s accompanied by 7-peaks. An efficient numerical procedure is developed lor the s o lution of the non-linear scaling equations for the master functions. A schematic three component model is used to fit quantitatively the dielectric loss spectra of polyvinylscetate, ortlmterphenyl, CaKNOj and poly propylene glycol, which all deviate strongly from the Kohlrausch decay pattern. The model yields also triple resonances of o7-S-peaks.

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Section: Examples For A-relaxation Susceptibilitiesmentioning

confidence: 99%

Comments on the alpha -peak shapes for relaxation in supercooled liquids

Fuchs

Götze

Hofacker

et al. 1991

J. Phys.: Condens. Matter

145

152

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“…We follow the general assumption that the end-to-end vector fluctuations of certain linear chain polymers made up of dipolar monomers can be measured by dielectric spectroscopy, 63 and for general architectures discuss the dynamical radius of gyration correlation function, P(t), with respect to dielectric measurements.…”

Section: ͑9͒mentioning

confidence: 99%

Mode-coupling theory of the slow dynamics of polymeric liquids: Fractal macromolecular architectures

Fuchs

Schweizer

1997

The Journal of Chemical Physics

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Recently a mode coupling theory for the dynamics of solutions and melts of entangled linear chain polymers has been developed. We report the extension of this approach to macromolecular architectures different from linear chains. Specifically, this work addresses recent experimental findings on melts of ring shaped polymers, small spherical micro-networks, and linear chains in two dimensions. The mechanical and dielectric response, diffusion, and molecular relaxation times of macromolecules modeled by fractal mass distributions are studied. The distribution is chosen to be Gaussian and then is uniquely determined from the experimentally measured scaling of macromolecular size (R g ) with degree of polymerization (N), i.e., R g ϰ N . The exponent and the spatial dimension d determine the large N scaling of the transport coefficients and the exponents describing intermediate time anomalous diffusion. Within the theory, entanglement corrections to the single polymer Rouse dynamics are effective for Ͻ2/d only. There, we find D ϰ N 2dϪ5 for the diffusion coefficient and that the ratio D D /R g 2 is almost constant, where D is the terminal relaxation time. Using independent input from equilibrium liquid state theories, the magnitude and scaling with macromolecular density and segment length of the dynamical properties is determined. It is also found that macromolecular interpenetration requires progressively higher densities and consequently entanglements become less effective with fractal dimension 1/ approaching the spatial dimension. © 1997 American Institute of Physics. ͓S0021-9606͑97͒50901-9͔

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“…Apart for the pendant ethyl group in place of the methyl group, POB has the same chemical structure as PPG (their structures are depicted in Figure 1). PPG has been the subject of many studies, by dielectric spectroscopy 10,14,15,57,58,59,60,61,62,63 and other techniques 64,65,66,67 .…”

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confidence: 99%

Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

Casalini

Roland

2005

Macromolecules

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Dielectric spectroscopy measurements over a broad range of temperature and pressure were carried out on poly(oxybutylene) (POB), a type-A polymer (dielectrically-active normal mode). There are three dynamic processes appearing at lower frequency, the normal and segmental relaxation modes, and a conductivity arising from ionic impurities. In combination with pressure-volume-temperature measurements, the dielectric data were used to assess the respective roles of thermal energy and density in controlling the relaxation times and their variation with T and P. We find that the local segmental and the global relaxation times are both a single function of the product of the temperature times the specific volume, with the latter raised to the power of 2.65. The fact that this scaling exponent is the same for both modes indicates they are governed by the same local friction coefficient, an idea common to most models of polymer dynamics. Nevertheless, near T g , their temperature dependences diverge. The magnitude of the scaling exponent reflects the relatively weak effect of density on the relaxation times. This is usual for polymers, as the intramolecular bonding, and thus interactions between directly bonded segments, are only weakly sensitive to pressure. This insensitivity also means that the chain end-to-end distance is invariant to P, conferring a near pressure-independence of the (density-normalized) normal mode dielectric strength.The ionic conductivity dominates the low frequency portion of the spectra. At lower temperatures and higher pressures, this conductivity becomes decoupled from the relaxation modes (different T-dependence), and exhibits a significantly weaker density effect. At frequencies higher than the structural relaxation, both an excess wing on the flank of the α-peak and a secondary relaxation are observed. From their relative sensitivities to pressure, we ascribe the former to an unresolved Johari-Goldstein (JG) relaxation, while the higher frequency peak is unrelated to the glass transition. These designations are consistent with the relaxation time calculated for the JG process. 2The dynamic properties of the POB are essentially the same as those of polypropylene glycol, in accord with their similar chemical structures. However, POB is less fragile (weaker T gnormalized temperature dependence), its relaxation times less sensitive to density changes, and facilitating the measurements herein, its normal mode has a substantially larger dielectric strength

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Dielectric Relaxation in Liquid Polypropylene Oxides

Cited by 168 publications

References 33 publications

Comments on the alpha -peak shapes for relaxation in supercooled liquids

Comments on the alpha -peak shapes for relaxation in supercooled liquids

Mode-coupling theory of the slow dynamics of polymeric liquids: Fractal macromolecular architectures

Temperature and Density Effects on the Local Segmental and Global Chain Dynamics of Poly(oxybutylene)

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