Direct Observation of Dynamic Tube Dilation in Entangled Polymer Blends: A Combination of Neutron Scattering and Dielectric Techniques

Molina, Paula Malo de; Alegría, Ángel; Allgaier, Jürgen; Kruteva, Margarita; Hoffmann, Ingo; Prévost, Sylvain; Monkenbusch, M.; Richter, D.; Arbe, Arantxa; Colmenero, Juan

doi:10.1103/physrevlett.123.187802

Cited by 9 publications

(13 citation statements)

References 28 publications

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“…Figure shows the results obtained for the normalized chain dynamic structure factor S ( Q , t )/ S ( Q ,0) corresponding to long chains in the blend with the 18-arm star additive (ϕ L = 0.5). The results corresponding to the blends with the 8-arm star additive, and with the short linear additivethat were previously reportedare also included here for comparison. We have also included in the figure as a reference (dashed lines) the fitting curves describing the S ( Q , t )/ S ( Q ,0) data, corresponding to the pure PI-80k sample .…”

Section: Resultsmentioning

confidence: 99%

“…The results corresponding to the blends with the 8-arm star additive, and with the short linear additivethat were previously reportedare also included here for comparison. We have also included in the figure as a reference (dashed lines) the fitting curves describing the S ( Q , t )/ S ( Q ,0) data, corresponding to the pure PI-80k sample . These fitting curves correspond to a de Gennes-like model for S ( Q , t )/ S ( Q ,0) with a value of the effective tube of d 0 = 64 Å (see ref for the details), which will be explained in detail in Section .…”

Section: Resultsmentioning

confidence: 99%

“…SANS measurements were performed on the instrument D11 at the Institut Laue-Langevin (ILL) in Grenoble, France. , Three different configurations were used, with a wavelength of λ = 6.0 Å (full width at half-maximum (FWHM) 9%), sample-to-detector (SD) distances of 1.4, 8, and 39 m, and collimations of 10.5, 8, and 40 m, respectively, covering a Q range of 0.02–5 nm –1 . The data were reduced using ILL in-house software, correcting measured intensities for the transmission, dead-time, detector background (with B4C as a neutron absorber at the sample position), sample background (empty cell), and the absolute scale (obtained from a tabulated value of a 1.5 mm sheet of Plexiglas).…”

Section: Experimental Sectionmentioning

confidence: 99%

“…Then, the time dependence of the CR or DTD mechanism at the molecular level is poorly known. Some MD-simulation studies have been trying to address this problem from a microscopic (molecular) point of view. , In a recent study, we have shown that the time-dependent tube dilation in isofrictional polymer blends can be directly observed by neutron spin echo (NSE) techniques as an additional time dependence of the dynamic structure factor in the local reptation regime. We also identified the characteristic time driving tube dilation as the terminal time of the short component of the blend.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…[1][2][3][4][5][6] This gives rise to questions as how much the microscopic relaxation dynamics of a polymeric material, which decides its dynamic mechanical properties and phase stability, can be modified after loading of an additive, in particular when that additive has a similar molecular structure as the polymer chains. [7] In previous experimental studies of some miscible polymer blends, dynamical heterogeneity was observed, indicated by a broad glass transition temperature and/or thermo-rheological complexity. [8][9][10][11][12][13] This thermo-rheological complexity of certain miscible polymer blends was attributed to either differences in the component's parameters to ε AA = 0.80, ε BB = 2.0, and ε AB = 1.6 (note that the resulting interaction energies are negative at the potential minima), with oligomer and polymer monomers being categorized as the fast (A) and slow (B) component, respectively.…”

Section: The Relaxation Spectra Of the Components In Polymer Blends Dmentioning

confidence: 96%

Rouse Mode Analysis of Relaxation in Polymer Blends

Cao

Merlitz

et al. 2020

Macro Theory & Simulations

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The relaxation spectra of the components in polymer blends determine the dynamic mechanical properties of the corresponding composite materials, which, in thermo‐rheological studies, show a delicate dependence on their chemical and physical properties as well as its bulk composition. A molecular dynamics simulation based Rouse mode analysis is performed to detect the relaxation spectra of the component chains on all length scales ranging from one monomer to the whole chain size, indicating that the bulk composition dominates the relaxation dynamics of the components in miscible polymer blends. The relaxation of component chains accelerates on all length scales as increasing the free volume available to monomers to move, with the dependence of mobility shift on composition being quantified by a Williams–Landel–Ferry like function governing the time‐composition superposition. Role of the chain connectivity induced self‐concentration effect on chain relaxation in polymer blends is discussed and proved to be limited, which leads to a visible but subtle length‐scale dependent rheological complexity as the composition is varied.

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Chain Entanglements and Interlamellar Links in Isotactic Polybutene-1: The Effect of Condis Crystals and Crystallization Temperature

et al. 2022

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Chain entanglements, which reside in the amorphous phase of semicrystalline polymers, influence many macroscopic properties of polymers. There are different opinions about the role of crystallization and subsequent melting in the entanglement density. Isotactic polybutene-1 (iPB-1) was selected for this study. Crystallization of this polymer from an equilibrated melt led to the formation of conformationally disordered (condis) form II crystals with high chain mobility enabling long-range chain diffusion, which facilitates chain disentangling. After the crystallization was accomplished, the entanglement network was frozen during the phase transition to stable form I with the polymer backbone fixed in the crystals. All experiments were performed for samples with form I crystals. A significant decrease in the entanglement density occurred during slow crystallization of iPB-1 with M w = 115 kg/mol. The disentangling degree was lower at faster crystallization and for iPB-1 with a higher molecular weight M w = 711 kg/mol. The entanglement density increased during melting and approached its equilibrium value at the end of melting. The estimated entanglement density of the equilibrated iPB-1 melt coincided within approximately 8% with the value reported in a rheological study. In addition to the entanglement density, the relative density of chain segments, which are anchored to crystallites and form interlamellar links, was estimated. The density was found to increase with increasing molecular weight, and it was larger at a faster crystallization rate due to thinner lamellae and a smaller long period on the periodic lamellar structure.

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Direct Observation of Dynamic Tube Dilation in Entangled Polymer Blends: A Combination of Neutron Scattering and Dielectric Techniques

Cited by 9 publications

References 28 publications

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

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

Rouse Mode Analysis of Relaxation in Polymer Blends

Chain Entanglements and Interlamellar Links in Isotactic Polybutene-1: The Effect of Condis Crystals and Crystallization Temperature

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