Viscoelastic Relaxation of Linear Polyisoprenes: Examination of Constraint Release Mechanism

Sawada, Toshiaki; Qiao, Xiuying; Watanabe, Hiroshi

doi:10.1678/rheology.35.11

Cited by 26 publications

(120 citation statements)

References 29 publications

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“…14,15,16,19) The h 0 data of low-M probes (filled circles) are consistent with the known crossover from the non-entangled to entangled regime (from…”

Section: Overview Of Datasupporting

confidence: 76%

“…Thus, we note a contrast between the viscoelastic and dielectric losses, G" and e", the latter clearly exhibiting a peak due to the probe relaxation (cf. with h 0 data of higher-M PI obtained previously 14,15,16,19) (unfilled circles). The data are plotted against the number of entanglement per chain, M/M e .…”

Section: Overview Of Datamentioning

confidence: 80%

“…This article presents details of this result and discusses the onset of entanglement in relation to competition of constraint release (the basic mechanism underlying the DTD process) and reptation. 14,15,19) were utilized as the elution standards.…”

Section: )mentioning

confidence: 99%

“…16,19) Blends of PI 1.1M sample (matrix) with one of the two low-M PI samples (probes), with the volume fraction u 1 = 0.1 for the latter, were subjected to dielectric and linear viscoelastic measurements. The blends were prepared by dissolving prescribed masses of the components in benzene at a concentration ~5 wt% and then allowing benzene to thoroughly evaporate at 50 °C in high vacuum for 48 h.…”

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confidence: 99%

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Dielectric and Viscoelastic Behavior of Low-M Linear Polyisoprene Blended in Long Matrix

Watanabe

2014

J. Soc. Rheol., Jpn

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Cis-polyisoprene (PI) has the type-A dipole parallel along the chain backbone thereby exhibiting slow dielectric relaxation that reflects the global chain motion (end-to-end vector fluctuation). For linear PI probes having the molecular weights M 1 in a range between 21.4× 10 3 and 179 × 10 3 (M 1 /M e = 4-36) and being blended with a longer PI matrix (M 2 = 1.12 × 10 6 ), a recent dielectric experiment revealed that the probe relaxation is moderately retarded on blending and this retardation is enhanced with decreasing M 1 in this range; cf. Matsumiya et al., Macromolecules, 46, 6067 (2013). Those dielectric data were analyzed within the context of the tube model to suggest that the probe relaxation in monodisperse bulk occurs through reptation along a partially dilated tube that wriggles in a fully dilated tube. However, this mechanism of relaxation is expected to vanish on a further decrease of M 1 because the tube itself loses its sound meaning for small M 1 . This expectation was examined in this study. Dielectric and viscoelastic tests revealed that the retardation of the probe relaxation on blending becomes minor (though not negligible) on a decrease of M 1 to 7.8× 10 3 (@ 1.6M e ), as expected.

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“…14,15,16,19) The h 0 data of low-M probes (filled circles) are consistent with the known crossover from the non-entangled to entangled regime (from…”

Section: Overview Of Datasupporting

confidence: 76%

Section: Overview Of Datamentioning

confidence: 80%

Section: )mentioning

confidence: 99%

mentioning

confidence: 99%

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Dielectric and Viscoelastic Behavior of Low-M Linear Polyisoprene Blended in Long Matrix

Watanabe

2014

J. Soc. Rheol., Jpn

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“…49 Results are shown in Figure 14. Again, incorporation of the CR-activated CLF (eq 13) having the characteristic time given by eqs 17 gives a good agreement between the data in the dominant part of relaxation and the calculated curve.…”

Section: 21mentioning

confidence: 99%

Dynamic Dilution Effect in Binary Blends of Linear Polymers with Well-Separated Molecular Weights

et al. 2014

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We investigate and model the viscoelastic properties of binary blends composed of linear chains. These systems are indeed very suitable to test the validity and the limit of the constraint release (CR) process and dynamic tube dilution and to determine the value of the dynamic dilution exponent α. We first focus on binary blends containing barely entangled short chains. In such a case, we show that the tension re-equilibration process previously observed [ van Ruymbeke van Ruymbeke Macromolecules2012452085] can be correctly described as a CR-activated contour length fluctuation (CLF) process, which takes place along the fully dilated tube and is governed by the intrinsic Rouse time of a long–long entanglement segment. In addition, reptation is considered to take place along the fully dilated tube. We also show that this CR-activated CLF process speeds up the relaxation of the long chains, which naturally leads to an effective dilution exponent α equal to 4/3, despite the fact that the modeling is based on α = 1. This result is in agreement with the experimental data. Then, we analyze the rheological behavior of binary blends containing entangled short chains. In such a case, we show that the CR-activated CLF also takes place, but with a delay time being necessary for the long chain to explore the dilated tube. This approach is tested for several binary blends, showing an improved quality of the predictions compared to previous tube modeling on the same blends. Indeed, by considering the chain motions on two different length scales, a larger fraction of the long chains relax at intermediate frequencies (through the tension re-equilibration) before their reptation, leading to an effective dilution exponent larger than 1 as determined from the low-frequency plateau modulus.

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Tube Dilation in Isofrictional Polymer Blends Based on Polyisoprene with Different Topologies: Combination of Dielectric and Rheological Spectroscopy, Pulsed-Field-Gradient NMR, and Neutron Spin Echo (NSE) Techniques

et al. 2020

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We address the dynamics of isofrictional bimodal polyisoprene (PI) blends and emphasize the effect of concentration and topology of the short component on the dynamics of the long-chain component. The experiments were performed on blends of long well-entangled linear chains with shorter linear and star-branched chains varying systematically the concentration of the short component (additive). Small-angle neutron scattering showed that the conformation of the long chains does not change either with concentration or with the additive topology. Applying different spectroscopic techniques, we studied the terminal times of both the long chain and the additives. Thereby, the dielectric and viscoelastic terminal times for the long-chain dynamics, as well as the diffusion times deduced from pulsed-field-gradient (PFG)-NMR measurements, follow the same scaling behavior as a function of the volume fraction of the long chains (ϕ L ). For the case of the linear additive, the scaling τ L ∼ ϕ L is observed in the full concentration range covered (0.1 ≤ ϕ L ≤ 1). In the case of the star additives, deviations from this scaling law are evident at ϕ L ≲ 0.4. The zero-shear viscosity scales as η 0 ∼ ϕ L 3 for ϕ L ≳ 0.4. Deviations are observed at lower values of ϕ L for both additive topologies. On the other hand, the terminal relaxation time of the short chain or the arm retraction time for the stars obtained from dielectric spectroscopy (DS) is only weakly affected by blending and stays nearly constant over the full concentration range. However, the diffusion times of both types of additives depend significantly on ϕ L . Finally, measuring the dynamic structure factor by neutron spin echo (NSE), we directly observe the process of constraint removal at the molecular scale. These results are discussed in terms of the different theoretical approaches available. Thereby, the nearly quantitative agreement of the rheological results with the Read extension of the Viovy theory for long-chain volume fractions ϕ L ≥ 0.5 is emphasized. On the other hand, the low ϕ L results cannot be accounted for. Also, predictions of the tension equilibration mechanism leading to an enhanced ϕ L -dependence are not supported by our data.

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Viscoelastic Relaxation of Linear Polyisoprenes: Examination of Constraint Release Mechanism

Cited by 26 publications

References 29 publications

Dielectric and Viscoelastic Behavior of Low-M Linear Polyisoprene Blended in Long Matrix

Dielectric and Viscoelastic Behavior of Low-M Linear Polyisoprene Blended in Long Matrix

Dynamic Dilution Effect in Binary Blends of Linear Polymers with Well-Separated Molecular Weights

Tube Dilation in Isofrictional Polymer Blends Based on Polyisoprene with Different Topologies: Combination of Dielectric and Rheological Spectroscopy, Pulsed-Field-Gradient NMR, and Neutron Spin Echo (NSE) Techniques

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