Effect of temperature on the terminal relaxation of branched polydimethysiloxane

Roland, C. M.; Santangelo, P. G.

doi:10.1016/s0022-3093(02)01528-4

Cited by 18 publications

(11 citation statements)

References 20 publications

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“…Transient 2 and dynamic mechanical 3 measurements on linear PDMS have a long history, while more recently the rheology of branched PDMS has been investigated. 4 Good agreement with predictions of the Rouse model has been found in these studies.…”

Section: Introductionsupporting

confidence: 75%

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Ding¹,

Novikov²,

Sokolov³

et al. 2004

Macromolecules

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A theoretical model for the chain modes' contribution to the depolarized light scattering (DLS) spectrum of polymers is developed. It is shown that the frequency dependence of the DLS susceptibility spectrum is similar to that of the shear loss modulus. Specifically, the contribution of chain modes to the DLS spectrum is composed of a series of Lorentzians (single-exponential processes) having the same amplitude. The relaxation time associated with each mode follows the Rouse prediction, but with a value equal to one-half the mechanical Rouse time. DLS spectra of poly(dimethylsiloxane) melts with different molecular weights have been analyzed in the framework of the model. Reasonable agreement on both qualitative and quantitative levels is observed. In particular, the relaxation time of the longest Rouse mode extracted from DLS spectra is consistent with that from viscosity measurements.

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Section: Introductionsupporting

confidence: 75%

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Ding¹,

Novikov²,

Sokolov³

et al. 2004

Macromolecules

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“…We noted similar behavior in other branched polyethylenes. On the basis of our explanation for this behavior, we expect that the value of n should not vary with temperature for polymers with equivalent temperature dependencies for the terminal flow of branched and linear architectures (e.g., polyisobutylene35, 36 and polydimethylsiloxane37). For all polymer systems, the accuracy of n , and hence ϕ b , will be slightly affected by the evaluation of δ c from plateaus or inflections versus maxima in δ(ω).…”

Section: Resultsmentioning

confidence: 92%

Extent of branching from linear viscoelasticity of long‐chain‐branched polymers

Robertson

García-Franco

Srinivas

2004

J Polym Sci B Polym Phys

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We present new results and examine literature data concerning the linear viscoelastic behavior of polyethylene with sparse to intermediate levels of long‐chain branching (LCB). These branched polymers displayed a common rheological signature, namely, a region of frequency‐independent loss tangent along with the corequisite scaling of the storage and loss moduli to the same frequency exponent. This apparent power‐law response occurred within a finite frequency window and bore resemblance to the behavior of physical gels. The appearance of this region, however, was the consequence of the presence of two distinct, yet partially overlapping, terminal relaxation processes. After considering the analogous relaxation behavior of wholly linear polymers with bimodal molecular weight distributions, we considered the polymers with LCB as blends of linear and branched species to develop a simple method of quantifying the extent of LCB. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1671–1684, 2004

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“…Their low glass transition temperature in combination with excellent thermal stability enables measurements over an enormous range of temperatures. [15][16][17] Monodisperse polysiloxanes are readily available in a range of molecular weights, and with a variety of chemical side-groups. In this paper, we describe dielectric measurements on polymethylphenylsiloxanes (PMPS) of varying molecular weight, carried out as a function of both temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature and Pressure on Segmental Relaxation in Polymethylphenylsiloxane

Pawlus

Rzoska

Zioło

et al. 2003

Rubber Chemistry and Technology

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Segmental relaxation in a series of polymethylphenylsiloxanes (PMPS) was studied using dielectric spectroscopy. The measurements covered a temperature range of more than 40 deg at pressures from ambient to 115 MPa. The results confirmed that the shape of the loss peak is independent of temperature, pressure and molecular weight. Consequently, the T g -scaled dependence of the relaxation times was also independent of molecular weight. The pressure dependence of the relaxation times was characterized by means of the activation volume. This quantity changes markedly with pressure at a given temperature. However, the activation volume at the respective glass transition temperatures of the PMPS are essentially invariant to molecular weight. Finally, we measured the dependence of T g on pressure, with the results well-described by the Andersson equation.

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Effect of temperature on the terminal relaxation of branched polydimethysiloxane

Cited by 18 publications

References 20 publications

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Observation of Chain Dynamics in Depolarized Light Scattering Spectra of Polymers

Extent of branching from linear viscoelasticity of long‐chain‐branched polymers

Effect of Temperature and Pressure on Segmental Relaxation in Polymethylphenylsiloxane

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