Reptation and constraint release in linear polymer melts: an experimental study

Seggern, J. von; Klotz, S.; Cantow, H.‐J.

doi:10.1021/ma00011a039

Cited by 53 publications

(70 citation statements)

References 5 publications

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“…Friction coefficients in the two descriptions are derived from the solution of the memory functions, while the rescaling of the simulation time is obtained from the entropic contribution, which accounts for the intramolecular degrees of freedom neglected in the soft-colloid representation. Theoretical predictions compare well against UA MD simulations [14,[45][46][47] and experiments [39,[48][49][50][51]. We also calculate the diffusion coefficient for new polyethylene (PE) samples in thermodynamics conditions for which UA MD data are not available.…”

Section: Introductionmentioning

confidence: 71%

“…We selected UA MD simulations as our test (Table I) because they have been shown to reproduce with a high level of accuracy the dynamical properties of PE melts, such as diffusion and viscosity [71,72]. We also compared predictions of rescaled MS-MD simulations with experiments for samples with temperature T = 509 K, monomer site density ρ = 0.0315302 sites/Å 3 , and N = 36, 72, 106, 130, 143, 192, and 242 [39,[48][49][50][51]. Our MS-MD simulations, properly rescaled, provided good quantitative predictions of the diffusion coefficient for those systems [31].…”

Section: Mesoscale Simulationsmentioning

confidence: 99%

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First-principle approach to rescale the dynamics of simulated coarse-grained macromolecular liquids

2011

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We present a detailed derivation and testing of our approach to rescale the dynamics of mesoscale simulations of coarse-grained polymer melts (I. Y. Lyubimov, J. McCarty, A. Clark, and M. G. Guenza, J. Chem. Phys. 132, 224903 (2010)). Starting from the first-principle Liouville equation and applying the Mori-Zwanzig projection operator technique, we derive the generalized Langevin equations (GLEs) for the coarse-grained representations of the liquid. The chosen slow variables in the projection operators define the length scale of coarse graining. Each polymer is represented at two levels of coarse graining: monomeric as a bead-and-spring model and molecular as a soft colloid. In the long-time regime where the center-of-mass follows Brownian motion and the internal dynamics is completely relaxed, the two descriptions must be equivalent. By enforcing this formal relation we derive from the GLEs the analytical rescaling factors to be applied to dynamical data in the coarse-grained representation to recover the monomeric description. Change in entropy and change in friction are the two corrections to be accounted for to compensate the effects of coarse graining on the polymer dynamics. The solution of the memory functions in the coarse-grained representations provides the dynamical rescaling of the friction coefficient. The calculation of the internal degrees of freedom provides the correction of the change in entropy due to coarse graining. The resulting rescaling formalism is a function of the coarse-grained model and thermodynamic parameters of the system simulated. The rescaled dynamics obtained from mesoscale simulations of polyethylene, represented as soft-colloidal particles, by applying our rescaling approach shows a good agreement with data of translational diffusion measured experimentally and from simulations. The proposed method is used to predict self-diffusion coefficients of new polyethylene samples.

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Section: Introductionmentioning

confidence: 71%

Section: Mesoscale Simulationsmentioning

confidence: 99%

First-principle approach to rescale the dynamics of simulated coarse-grained macromolecular liquids

2011

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“…The increase of d and the decrease of D for probe chains in a high-M matrix can result only from the suppression of mutual chain relaxation effects, while fluctuations remain intact. Since significantly lower scaling exponents than expected are observed for probe systems [28,[31][32][33], the influence of surrounding chains motion has to be higher than usually accepted and the influence of fluctuations less [8][9][10]. However, considering that the deviations from ideal reptation exponents (about 0.3-0.4) and the Z crossover positions (about 100) are similar for both rheology and diffusion, it is possible to preserve the 0 D s Z scaling proposed by Lodge [6,29].…”

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confidence: 80%

“…Since tracer diffusion results from the diffusion of a probe chain in a high-M matrix, the two environments for D tr and D s are exactly the same as those in our rheological tests. Lodge [6] has collected extensive literature data on self-diffusion of entangled hydrogenated PBD [26 -30], and Wang [31] has further taken into account additional tracer diffusion data [28,32]. Interestingly, the two authors have reached very different conclusions from almost the same set of selfdiffusion data (Fig.…”

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confidence: 99%

Do Deviations from Reptation Scaling of Entangled Polymer Melts Result from Single- or Many-Chain Effects?

2006

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By studying the relaxation of small amounts of short entangled "probe" chains in a high molecular weight matrix, we show that the deviations from reptation scaling of the longest relaxation time are not as much dominated by single-chain effects (usually referred to as contour length fluctuations or CLF) as assumed by current mesoscopic models but also originate to a very significant extent from mutual chain relaxation effects. This result is in fact consistent with literature data on tracer and self-diffusion. Moreover, tube theories also overpredict the influence of CLF on the plateau modulus. Improved theories, simulations, and careful experiments are urgently needed to resolve this important question.

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“…Examples are measurements of the shear viscosity 9,10 or plateau modulus, 3 both by means of rheometry, and measurements of self-diffusion coefficients, e.g., by means of NMR field-gradient diffusometry, 9,10 forward recoil spectroscopy, 11 or scanning infrared microscopy. 12 …”

Section: Introductionmentioning

confidence: 99%

A time-integrated estimate of the entanglement mass in polymer melts in agreement with the one determined by time-resolved measurements

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Briels

2004

The Journal of Chemical Physics

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Effects of alignment layer thickness on the pretilt angle of liquid crystals APL: Org. Electron. Photonics 3, 270 (2010) Effects of alignment layer thickness on the pretilt angle of liquid crystals Appl. Phys. Lett. 97, 243306 (2010) Field-theoretic model of inhomogeneous supramolecular polymer networks and gels J. Chem. Phys. 133, 174903 (2010) Origin of translocation barriers for polyelectrolyte chains JCP: BioChem. Phys We make a critical examination of how the entanglement molecular mass M e is determined from various measurable quantities. We are guided by reptation theory, where it is assumed that characteristic relaxations abruptly change and become equal to those of a chain moving in a Gaussian tube, as soon as the corresponding length scales surpass the tube diameter d or similarly as soon as the corresponding mass surpasses a critical value. Taking this critical mass as a definition of the ''reptational'' entanglement mass, we observe that all methods based on time-resolved quantities, such as the single-chain dynamic structure factor S(q,t) and the zero-shear relaxation modulus G(t), give the same result. We observe that such a value differs, beyond error bars, from that obtained from the plateau modulus, which is a time-integrated quantity. We have investigated an alternative definition of entanglement mass in terms of time-integrated quantities and observe that the value of this specific entanglement mass is consistent with that obtained from the time-resolved observables. We comment on possible reasons for the plateau modulus discrepancy.

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Reptation and constraint release in linear polymer melts: an experimental study

Cited by 53 publications

References 5 publications

First-principle approach to rescale the dynamics of simulated coarse-grained macromolecular liquids

First-principle approach to rescale the dynamics of simulated coarse-grained macromolecular liquids

Do Deviations from Reptation Scaling of Entangled Polymer Melts Result from Single- or Many-Chain Effects?

A time-integrated estimate of the entanglement mass in polymer melts in agreement with the one determined by time-resolved measurements

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