Monte Carlo Prediction of the Structure Factor of Polyethylene in Good and ϑ-Solvents

Destrée, M.; Lyulin, Alexey V.; Ryckaert, Jean‐Paul

doi:10.1021/ma951063i

Cited by 20 publications

(42 citation statements)

References 27 publications

(78 reference statements)

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“…To appreciate the quality of the local potential model, we checked in a previous paper 39 the PP structural single chain properties using Monte Carlo methods on long single chains at point. 40 In particular, the Kuhn segment estimates for the various tactic forms of PP at theta point ͑400 K͒ were determined as 6.1Ϯ0.1 Å for iPP, 7.9Ϯ0.3 Å for sPP and 6.3Ϯ0.2 Å for aPP, in rather good agreement with experimental data 41 and with earlier theoretical estimates based on rotational isomeric state ͑RIS͒ calculations. 42 These results already suggest a smaller static flexibility ͑larger persistence length͒ of sPP with respect to iPP, the 1-5 interactions forcing more tt correlations between successive dihedral angles in the sPP form.…”

Section: Discussionsupporting

confidence: 80%

Local dynamics of isotactic and syndiotactic polypropylene in solution

Destrée

Lauprêtre

Lyulin

et al. 2000

The Journal of Chemical Physics

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The local dynamics of polypropylene ͑PP͒ in solution is studied by 13 C NMR relaxation and by molecular dynamics ͑MD͒ simulation via the orientational autocorrelation function ͑OACF͒ of C-H bonds. The interpretation protocol of this function proposed by Dejean de la Bâtie, Lauprêtre and Monnerie ͑DLM͒ ͓R. Dejean de la Bâtie, F. Lauprêtre, and L. Monnerie, Macromolecules 21, 2045͑1988͔͒ is applied and tested on new NMR measurements of the various microstructures of polypropylene. This interpretation scheme of the OACF is supported by a detailed study employing simulated PP trajectories in an atomistic heat bath. MD simulations indicate that, quite generally, the correlation time for segmental motions, 1 , extracted from the DLM motional model is closely linked with the mean time between conformational jumps. Both experiments and simulations suggest a slightly higher mobility of meso sequences by comparison with racemic sequences. Our analysis of the microscopic aspects of the segmental dynamics and its manifestation in motional models allows us to trace the microscopic origin of the larger mobility of meso sequences.

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Section: Discussionsupporting

confidence: 80%

Local dynamics of isotactic and syndiotactic polypropylene in solution

Destrée

Lauprêtre

Lyulin

et al. 2000

The Journal of Chemical Physics

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“…25 This value of * differs slightly from the value *ϭ0.53 quoted in Ref. 23 which was obtained at the same temperature with much shorter chains and a slightly different n គ -butane torsional form.…”

Section: ͑23͒contrasting

confidence: 65%

“…17 We did experiments for Tϭ400 K using ϭ*͑400͒ϭ0.505 for Nϭ256 and 512, which model point conditions. 25 A few runs in good solvent at the same temperature were performed with ϭ0.01 for Nϭ256. All results have been produced with kϭ8 methylene units for the CBMC/reptation moves.…”

Section: A Sampling In the Fixed-f Single Chain Ensemblementioning

confidence: 99%

Single chain elasticity and thermoelasticity of polyethylene

Titantah

Pierleoni

Ryckaert

2002

The Journal of Chemical Physics

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Single-chain elasticity of polyethylene at $\theta$ point up to 90% of stretching with respect to its contour length is computed by Monte-Carlo simulation of an atomistic model in continuous space. The elasticity law together with the free-energy and the internal energy variations with stretching are found to be very well represented by the wormlike chain model up to 65% of the chain elongation, provided the persistence length is treated as a temperature dependent parameter. Beyond this value of elongation simple ideal chain models are not able to describe the Monte Carlo data in a thermodynamic consistent way. This study reinforces the use of the wormlike chain model to interpret experimental data on the elasticity of synthetic polymers in the finite extensibility regime, provided the chain is not yet in its fully stretched regime. Specific solvent effects on the elasticity law and the partition between energetic and entropic contributions to single chain elasticity are investigated.Comment: 32 pages with 5 figures included. Accepted as a regular paper on The Journal of Chemical Physics, August 2002. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physic

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“…It is remarkable how well the relation is obeyed given the realities of experimentation with a protein pore. In addition to the conditions of a dilute regime and water being a ''good'' solvent for the polymer (38,39), the derivation assumes that the pore is a narrow cylinder with a constant cross-sectional area. The actual diameter varies between 15 Å and 24 Å, even in the ␤-barrel, which is the most uniform part of the structure (Table 3).…”

Section: Discussionmentioning

confidence: 99%

Partitioning of a polymer into a nanoscopic protein pore obeys a simple scaling law

Movileanu

Bayley

2001

Proc. Natl. Acad. Sci. U.S.A.

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The dependence of the rate on polymer mass was examined for the reaction of four sulfhydryl-directed poly(ethylene glycol) reagents with cysteine residues located in the lumen of the staphylococcal ␣-hemolysin pore. The logarithms of the apparent rate constants for a particular site in the lumen were proportional to N, the number of repeat units in a polymer chain. The proportionality constant was ؊(a͞D) 5/3 , where a is the persistence length of the polymer (Ϸ3.5Å) and D is the diameter of the pore. Despite some incongruencies with the assumptions of the derivation, the result suggests that the polymers partition into the lumen of the pore according to the simple scaling law of Daoud and de Gennes, c pore͞csolution ‫؍‬ exp(؊N(a͞D) 5/3 ). Therefore, the measured reaction rates yield an estimate of the diameter of the pore and might be applied to determine the approximate dimensions of cavities within other similar proteins.T he interactions of polymers with proteinaceous channels and pores has been studied extensively (1, 2). The osmotic effects of polymers on the voltage-dependent anion channel of mitochondria (VDAC) and other channels have been examined (1,(3)(4)(5). Polymer partitioning into pores from concentrated solutions has been investigated in studies of single-channel conductance (6), access resistance (7,8), and single-channel noise (2,(8)(9)(10). The movement of nucleic acids through pores has been examined through their effects on single-channel conductance (11)(12)(13)(14). The effects of covalently attached polymers on the properties of channels and pores have also been investigated (15)(16)(17).Given the interest in this area, it is of fundamental importance to understand how polymers partition from dilute solution into protein pores. This problem has received attention by theoreticians. Notably, scaling theory has been used to estimate partition coefficients (18,19). Specifically, Daoud and de Gennes (20) found the partition coefficient (⌸) for polymers into a tube to bewhere c is the concentration, N is the number of units in a polymer chain, a is the persistence length of the polymer, and D is the diameter of the pore. This relation applies to a narrow tube both where the Flory radius of the polymer R F Ͼ D (20) and where R F Ϸ D (21, 22). It requires that the free energy of confinement of each segment (''blob'') of the polymer within the pore is k B T, where k B is the Boltzmann constant and T the absolute temperature. Interestingly, the scaling relation has not been subjected to extensive experimental examination. Several studies have shown that Ϫln ⌸ is linearly dependent on N (18, 23), but the appropriateness of the scaling coefficient Ϫ(a͞D) 5/3 has received less attention. Here, we analyze how poly(ethylene glycol) (PEG) molecules partition into the pore formed by staphylococcal ␣-hemolysin (␣HL). The dimensions of the ␣HL pore have been determined by crystallography ( Fig. 1; ref. 24). Importantly for the present study, the transmembrane portion of the pore is a ␤-barrel measuring Ϸ20...

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Monte Carlo Prediction of the Structure Factor of Polyethylene in Good and ϑ-Solvents

Cited by 20 publications

References 27 publications

Local dynamics of isotactic and syndiotactic polypropylene in solution

Local dynamics of isotactic and syndiotactic polypropylene in solution

Single chain elasticity and thermoelasticity of polyethylene

Partitioning of a polymer into a nanoscopic protein pore obeys a simple scaling law

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