Dielectric Spectroscopy on Dilute Blends of Polyisoprene/Polybutadiene: Effects of Matrix Polybutadiene on the Dynamics of Probe Polyisoprene

Adachi, Keiichiro; Wada, Takao; Kawamoto, Tatsuyoshi; Kotaka, Tadao

doi:10.1021/ma00114a011

Cited by 41 publications

(131 citation statements)

References 9 publications

(11 reference statements)

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“…Explanations of the anomalous viscosity versus molecular weight scaling, η ∼ M 3.5(0.2 , provided with models considering a single polymer in a frozen environment, therefore, appear accidental. The same, but frequency-resolved, dielectric measurements 9,10 stress that the rapid initial decay of the disentanglement process (or its shallow high-frequency loss modulus) persists even in the limit where reptation-like scaling of the final relaxation time is observed. This demonstrates the existence of a nonreptative effect, unrelated to constraint release, which determines the primary disentanglement step.…”

Section: Discussionmentioning

confidence: 78%

“…69 Adachi and co-workers have studied such a system, PI tracer in PBD melts, for varying tracer and matrix molecular weights. 9 They report the molecular weight dependence of the tracer dielectric relaxation time and the high-frequency asymptote of the disentanglement process in the dielectric spectrum. It is important to recall from paper I that PMC theory identifies two different mechanisms, one which is responsible for the initial decay of the end-toend vector correlation function, 〈P(t)‚P(0)〉/〈P(0)‚P(0)〉 -1 ∼ (t/N y τ 0 ) x , and two other ones which affect the dielectric relaxation time.…”

Section: Comparison With Melt and Solution Experimentsmentioning

confidence: 99%

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Polymer-Mode-Coupling Theory of Finite-Size-Fluctuation Effects in Entangled Solutions, Melts, and Gels. 2. Comparison with Experiment

Fuchs

Schweizer

1997

Macromolecules

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The predictions of polymer mode coupling theory for the finite size corrections to the transport coefficients of entangled polymeric systems are tested in comparison with various experimental data. It is found that quantitative descriptions of the viscosities, η, dielectric relaxation time, τ , and diffusion coefficients, D, of polymer melts can be achieved with two microscopic structural fit parameters whose values are in the range expected from independent theoretical or experimental information. An explanation for the (apparent) power law behaviors of η, τ , and D in (chemically distinct) melts for intermediate molecular weights as arising from finite size corrections, mainly the self-consistent constraint release mechanism, is given. The variation of tracer dielectric relaxation times from Rouse to reptationlike behavior upon changes of the matrix molecular weight is analyzed. Self-diffusion and tracer diffusion constants of entangled polymer solutions can be explained as well, if one further parameter of the theory is adjusted. The anomalous scaling of the tracer diffusion coefficients in semidilute and concentrated polystyrene solutions, D ∼ N -2.5 , is predicted to arise due to the spatial correlations of the entanglement constraints, termed "constraint porosity". Extensions of the theory to polymer tracer diffusion through poly(vinyl methyl ether) and polyacrylamide gels provide an explanation of the observation of anomalously high molecular weight scaling exponents in a range where the size of the tracer, Rg, already considerably exceeds the gel pore size, g. IntroductionThe microscopic polymer mode coupling (PMC) theory connects the dynamics of entangled polymeric systems to the underlying equilibrium liquid structure. This description therefore naturally includes corrections arising from the finite molecular weights of tracer or matrix polymers. In the preceding paper, 1 referred to as paper I, the PMC predictions with finite size corrections have been worked out for the transport properties of entangled solutions and melts and for polymer tracer motion in gels. In the present paper these results are compared with data from many experiments. As the PMC approach has been detailed in the preceding paper, 1 it shall be summarized only shortly in this section and then compared to alternative approaches. The resulting formulas of paper I will be referenced by the equation numbers of that paper with a prefix I.The PMC approach of paper I treats the Rouseentangled crossover problem in a simple interpolative manner. The PMC contributions capturing the entanglement corrections are combined with the Rouse, unentangled quantities, see eqs I.52 and I.68 for D, eqs I.55 and I.67 for η, and eqs I.58 and I.70 for τ . Appreciable deviations from the asymptotes for high molecular weights are therefore not explained by corrections of the Rouse dynamics to the asymptotic, entangled motion. In stark contrast to the contour length fluctuation model of Doi, 2,3 the repton model of Rubinstein, 4 and the Rouse-fluc...

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Section: Discussionmentioning

confidence: 78%

Section: Comparison With Melt and Solution Experimentsmentioning

confidence: 99%

Polymer-Mode-Coupling Theory of Finite-Size-Fluctuation Effects in Entangled Solutions, Melts, and Gels. 2. Comparison with Experiment

Fuchs

Schweizer

1997

Macromolecules

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“…This allows for stringent tests of theoretical models for the low frequency dynamics of polymers. 9,10 Boese and Kremer 13,14 carried out dielectric measurements on linear and branched polyisoprenes, quantifying the dependence of the breadth of the normal mode peak on molecular weight. They also reported that, while the normal mode for star-branched polyisoprene is shifted to lower frequencies relative to the linear polymer, the respective temperature dependencies were similar.…”

Section: Introductionmentioning

confidence: 99%

“…It is for this reason that most of the published dielectric data for the normal mode is limited to low molecular weight polymers. [6][7][8][9][10][11][12][13][14] This problem can be avoided by obtaining dielectric measurements at lower frequencies, using a time domain instrument. This has the additional benefit of providing data at the same frequencies and temperatures as mechanical spectrometers.…”

Section: Introductionmentioning

confidence: 99%

Normal Mode Relaxation in Linear and Branched Polyisoprene

Roland

Bero

1996

Macromolecules

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Dielectric spectroscopy was carried out on linear and three-arm star polyisoprenes (PI). The shape of the normal mode peak differed significantly from the corresponding mechanical terminal relaxation function, although the temperature dependencies measured for the two spectroscopies were similar. This represents a departure from the usual correlation between time and temperature dependencies. In accord with mechanical relaxation data on these same polymers, the normal mode peak is found to be broader and more sensitive to temperature for star-branched PI than for the linear polymer.

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“…Studies concerning the normal mode processes have been made extensively in the last two decades [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] for non-entangled and entangled PI's aiming to test several theoretical models for polymer chain motions, e.g., bead spring model, tube model and some modified versions of the original tube model. [21][22][23] Concerning the normal mode relaxation spectra of well entangled PI chains with narrow molecular weight distribution, it is also known that the tube model can not precisely reproduce the shapes of the dielectric loss curves especially in the higher frequency region than that corresponding to the longest (terminal) relaxation time.…”

Section: Introductionmentioning

confidence: 99%

Subchain Dynamics in Disordered Diblock Copolymer: Poly(isoprene-block-butadiene)

Urakawa¹,

Kido²,

Adachi³

2004

J. Soc. Rheol., Jpn

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We investigated the dielectric normal mode relaxation on diblock copolymers poly(isoprene-block-butadiene) (I-B) with several polyisoprene (PI)/polybutadiene (PB) compositions. Through the dielectric measurements on I-B, we can obtain information about the dynamics of the PI subchain since the PI block is labeled with type-A dipole but PB is not. At the same time, we carried out viscoelastic measurements on the same I-B samples to obtain information of the whole chain motion, especially the longest relaxation times and the plateau moduli. From these viscoelastic and dielectric data, we can directly compare the relaxation spectra of subchains with those predicted by the tube model. From such comparison, we have found that the end part of the chain relaxes faster than the theoretical prediction suggesting extra relaxation mechanisms other than reptation in the dynamics of chain ends.

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Dielectric Spectroscopy on Dilute Blends of Polyisoprene/Polybutadiene: Effects of Matrix Polybutadiene on the Dynamics of Probe Polyisoprene

Cited by 41 publications

References 9 publications

Polymer-Mode-Coupling Theory of Finite-Size-Fluctuation Effects in Entangled Solutions, Melts, and Gels. 2. Comparison with Experiment

Polymer-Mode-Coupling Theory of Finite-Size-Fluctuation Effects in Entangled Solutions, Melts, and Gels. 2. Comparison with Experiment

Normal Mode Relaxation in Linear and Branched Polyisoprene

Subchain Dynamics in Disordered Diblock Copolymer: Poly(isoprene-block-butadiene)

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