Effects of chain microstructure on the viscoelastic properties of linear polymer melts: polybutadienes and hydrogenated polybutadienes

Carella, José M.; Graessley, William W.; Fetters, Lewis J.

doi:10.1021/ma00142a059

Cited by 204 publications

(196 citation statements)

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“…Kremer and Grest found N e ϭ35 for their simulation model, 12 corresponding to C 97 , Richter et al derived N e ϭ136 monomers, i.e., C 136 , from their dynamic structure factor measurements, 36 and Carella et al measured N e ϭ65 monomers. 25 Our result is in any case smaller than those from the literature, but this may be due to the fact that our chains are too short to allow for a reasonable estimate of the entanglement length. In a future article, we will vary the chain length and focus more on the entanglement length.…”

Section: ͑39͒contrasting

confidence: 76%

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Uncrossability constraints in mesoscopic polymer melt simulations: Non-Rouse behavior of C120H242

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Briels

2001

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. 3, 11B610 (2009) Origin of translocation barriers for polyelectrolyte chains J. Chem. Phys. 131, 194903 (2009) Additional information on J. Chem. Phys. An important feature of a melt of long polymers is that the bonds of the chains cannot cross each other. This seemingly simple fact has a great impact on the long time dynamics and rheology of the material. In this paper an algorithm is described that explicitly detects and prevents bond crossings in mesoscopic simulations of polymers. The central idea is to view the bonds as slippery elastic bands which can become entangled. The method is applied to a simulation of a coarse-grained melt of C 120 H 242 , in which each chain is represented by six blobs. The long time dynamics and zero-shear rate rheology are investigated and the relative importance of uncrossability and chain stiffness is established. As a result of the uncrossability of the chains, we observe a subdiffusive exponent in the mean square displacement of the chains, a stretching of the exponential decay of the Rouse mode relaxations, an increase of relaxation times associated with large scales, and a slowing down of the relaxation of the dynamic structure factor. These results are in agreement with results from previous microscopic molecular dynamics simulations. Finally, an increased viscosity as compared to the Rouse model is observed, which is attributed to slowly decaying interchain stress components.

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Section: ͑39͒contrasting

confidence: 76%

“…A suitable choice seemed to be ϭ20 CH 2 units, which is still roughly one third of the entanglement length reported by Carella and coworkers. 25 The partial PMF's were calculated as minus kT times the logarithm of the measured distributions of blobs and fitted with simple analytical functions, as shown in Fig. 2.…”

Section: ͑6͒mentioning

confidence: 99%

Uncrossability constraints in mesoscopic polymer melt simulations: Non-Rouse behavior of C120H242

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Briels

2001

The Journal of Chemical Physics

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“…Considering the non-Gaussian character of the segment motion along a 1D contorted tube, in the frame of the reptation model the single chain dynamic structure factor and the selfcorrelation function agree quantitatively. The resulting tube diameter thereby is significantly larger than what is inferred from rheology [10,11].The PE and PEP samples were obtained from parent 1,4-polybutadiene and polyisoprene, respectively, which were synthesized by anionic polymerization [12]. PE and PEP were obtained by subsequent hydrogenation (deuteration).…”

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Direct Observation of the Transition from Free to Constrained Single-Segment Motion in Entangled Polymer Melts

et al. 2003

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We report a direct determination of the time dependent mean-squared segment displacement of a polymer chain in the melt covering the transition from free to constraint Rouse relaxation along the virtual tube of the reptation model. This has been achieved by a neutron spin-echo (NSE) measurement of the segmental self-correlation function as conveyed by the spin-incoherent scattering from two fully protonated polymer melts, polyethylene and polyethylene propylene. Within the scenario of de Gennes reptation model a transition of the time dependence of segmental mean-squared displacements from / t 1=2 to / t 1=4 is expected and clearly corroborated by the incoherent NSE results. DOI: 10.1103/PhysRevLett.90.058302 PACS numbers: 47.50.+d, 83.10.Kn Beyond a certain length polymer chains in a melt are subject to topological constraints of motion due to entanglements. As a consequence in high molecular weight (M) melts the viscosity becomes proportional to M 3:4 instead of / M for low molecular weights [1]. Furthermore in the viscoelastic properties of the melt at intermediate frequency ! a plateau in the modulus G ! , i.e., a transient rubbery network is observed [2]. A comprehensive recent review on viscoelasticity in entangled polymers may be found in Ref. [3]. Microscopically the single chain structure factor S Q; t as observed by neutron spin-echo (NSE) spectroscopy on deuterated melts containing a few h-labeled chains provides clear evidence for the restriction of motion [4,5] and corrobates all the features of the de Gennes dynamic structure factor for local reptation [6 -9]. The mean-squared segmental displacements hr 2 t i in the reptation scenario are given by an initial entropy driven Rouse motion [hr 2 t i / t 1=2 ] for t < e . At e the segmental diffusion slows down due to the ''contact'' with the ''walls'' of the virtual tube, further motion, termed local reptation, is a quasi-onedimensional Rouse relaxation along the contour of the virtual tube [hr 2 t i / t 1=4 ] [8]. This work presents the first direct measurements of hr 2 t i in space and time in terms of the proton self-correlation function of diffusing segments in long chain polyethylene (PE) and polyethylene propylene (PEP) melts. The measured self-correlation function very clearly displays the predicted crossover from free Rouse motion to local reptation. Considering the non-Gaussian character of the segment motion along a 1D contorted tube, in the frame of the reptation model the single chain dynamic structure factor and the selfcorrelation function agree quantitatively. The resulting tube diameter thereby is significantly larger than what is inferred from rheology [10,11].The PE and PEP samples were obtained from parent 1,4-polybutadiene and polyisoprene, respectively, which were synthesized by anionic polymerization [12]. PE and PEP were obtained by subsequent hydrogenation (deuteration). For the present investigations PE with a molecular weight M w 190 kg=mol and PEP with M w 80 kg=mol was chosen, both well in the entangled state.The incoher...

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“…In our previous work, the following considerations were taken into account: (1) λ should be large enough to allow for a significant increase in the time and length scales accessible to simulation, and (2) λ should not be so large that the "size" of a CG particle exceeds the typical diameter of the tube in the reptation picture, in other words the entanglement length. A suitable choice was λ = 20 CH 2 units, which is still roughly one third of the smallest entanglement length reported in the literature [19]. With this choice each polyethylene chain of 120 CH 2 units was represented by 6 CG particles.…”

Section: Polyethylenementioning

confidence: 99%

Ab-initio Coarse-Graining of Entangled Polymer Systems

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2007

Nanostructured Soft Matter

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Effects of chain microstructure on the viscoelastic properties of linear polymer melts: polybutadienes and hydrogenated polybutadienes

Cited by 204 publications

References 16 publications

Uncrossability constraints in mesoscopic polymer melt simulations: Non-Rouse behavior of C120H242

Uncrossability constraints in mesoscopic polymer melt simulations: Non-Rouse behavior of C120H242

Direct Observation of the Transition from Free to Constrained Single-Segment Motion in Entangled Polymer Melts

Ab-initio Coarse-Graining of Entangled Polymer Systems

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