Are polymer melts “ideal”?

Wittmer, J. P.; Beckrich, P.; Crevel, F.; Huang, Chien-Cheng; Cavallo, A.; Kreer, T.; Meyer, H.

doi:10.1016/j.cpc.2007.02.032

Cited by 14 publications

(26 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, they are consistently slightly higher than the theoretical value of 0.5 predicted by the random walk model. Wittmer et al 30,31 recently discussed deviations from Flory's ideality hypothesis. Using numerical data obtained from MC simulations with the bond fluctuation model and MD simulations with the bead-spring model, they were able to show that algebraically decaying residual correlations exist in the bond-bond correlation function for a polymer melt.…”

Section: Chain Statisticsmentioning

confidence: 99%

Molecular dynamics study of polymer conformation as a function of concentration and solvent quality

Zhou

Daivis

2009

The Journal of Chemical Physics

View full text Add to dashboard Cite

A coarse-grained model for molecular dynamics simulations of polymer solutions with variable solvent quality is proposed. This model allows solvent quality to be varied over the whole range from very poor to very good solvent conditions by varying a single parameter. The model has several advantages. All interactions are short ranged and repulsive, making the model very computationally efficient compared with other explicit solvent models that include the long-ranged attractive part of the interactions; the solvent is included explicitly, ensuring that the theta condition corresponds to a genuine cancellation of the solvent-mediated polymer-polymer interactions; and hydrodynamic interactions and entanglement can occur for all solvent conditions. The theta point is determined and the conformational properties of a 50-bead chain system are investigated over the whole concentration range from the dilute limit to the melt as a function of solvent quality.

show abstract

Section: Chain Statisticsmentioning

confidence: 99%

Molecular dynamics study of polymer conformation as a function of concentration and solvent quality

Zhou

Daivis

2009

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…Recently, Flory's hypothesis has been challenged both theoretically [11,12,13,14,15] and numerically for threedimensional solutions [16,17,18,19,20] and ultrathin films [21,22]. These studies suggest that intra-and interchain excluded volume forces do not fully compensate each other on intermediate length scales, leading to long-range intrachain correlations.…”

Section: Flory's Ideality Hypothesis Revisitedmentioning

confidence: 99%

“…(1). Elaborating and clarifying various points already presented briefly elsewhere [18,19,20], we focus here on melts of long and flexible polymers. Using two well-studied coarse-grained polymer models [23] various intrachain properties are investigated numerically as functions of s and compared with predictions from first-order perturbation theory.…”

Section: Flory's Ideality Hypothesis Revisitedmentioning

confidence: 99%

Intramolecular long-range correlations in polymer melts: The segmental size distribution and its moments

et al. 2007

Self Cite

View full text Add to dashboard Cite

Presenting theoretical arguments and numerical results we demonstrate long-range intrachain correlations in concentrated solutions and melts of long flexible polymers which cause a systematic swelling of short chain segments. They can be traced back to the incompressibility of the melt leading to an effective repulsion u(s) ≈ s/ρR 3 (s) ≈ c e / √ s when connecting two segments together where s denotes the curvilinear length of a segment, R(s) its typical size, c e ≈ 1/ρb 3 e the "swelling coefficient", b e the effective bond length and ρ the monomer density. The relative deviation of the segmental size distribution from the ideal Gaussian chain behavior is found to be proportional to u(s). The analysis of different moments of this distribution allows for a precise determination of the effective bond length b e and the swelling coefficient c e of asymptotically long chains. At striking variance to the short-range decay suggested by Flory's ideality hypothesis the bond-bond correlation function of two bonds separated by s monomers along the chain is found to decay algebraically as 1/s 3/2 . Effects of finite chain length are considered briefly. PACS numbers: 61.25.Hq,64.60.Ak,05.40.Fb * Electronic address: jwittmer@ics.u-strasbg.fr † URL: http://www-ics.u-strasbg.fr/~etsp/welcome.php 1 I. FLORY'S IDEALITY HYPOTHESIS REVISITEDA cornerstone of polymer physics. Polymer melts are dense disordered systems consisting of macromolecular chains [1]. Theories that predict properties of chains in a melt or concentrated solutions generally start from the "Flory ideality hypothesis" formulated already in the 1940s by Flory [2,3,4]. This cornerstone of polymer physics states that chain conformations correspond to "ideal" random walks on length scales much larger than the monomer diameter [1,4,5,6]. The commonly accepted justification of this mean-field result is that intrachain and interchain excluded volume forces compensate each other if many chains strongly overlap which is the case for three-dimensional melts [5]. Since these systems are essentially incompressible, density fluctuations are known to be small. Hence, all correlations are supposed to be short-ranged as has been systematically discussed first by Edwards who developed the essential statistical mechanical tools [6,7,8,9, 10] also used in this paper.One immediate consequence of Flory's hypothesis is that the mean-squared size of chain segments of curvilinear length s = m − n (with 1 ≤ n < m < N) should scale as R Both equations are expected to hold as long as the moment is not too high for a given segment length and the finite-extensibility of the polymer strand remains irrelevant [6].Deviations caused by the segmental correlation hole effect. Recently, Flory's hypothesis has been challenged both theoretically [11,12,13,14,15] and numerically for threedimensional solutions [16,17,18,19,20] and ultrathin films [21,22]. These studies suggest 2 that intra-and interchain excluded volume forces do not fully compensate each other on intermediate length scales, l...

show abstract

“…Standard Metropolis Monte Carlo is used to reversibly break and recombine the chains. 6,13,15 Branching and formation of closed rings are explicitly forbidden. As one expects from standard linear aggregation theory, the density of chains ρ N shows essentially a Flory distribution, ρ N ∼ exp(−N/ N ), with the mean chain size N scaling as N 2 ∼ ρ exp(E/k B T ).…”

Section: Algorithmic and Technical Issuesmentioning

confidence: 99%

“…See Figure 1 for a sketch of the notations used in this paper with n denoting the monomer index, N the number of monomers per chain, R(N ) the root-mean-square end-to-end distance, ρ the monomer number density, l the root-meansquare bond length, b ≡ lim N →∞ R(N )/N 1/2 the effective bond length and c ∞ = (b/l) 2 the dimensionless chain stiffness parameter. 2,4 Surprisingly, recent numerical studies [5][6][7][8][9] have demonstrated the power-law decay of the intrachain bond-bond correlation function P (s) ≡ l 0 · l 1 /l 2 , averaged over bond pairs of same curvilinear distance s, as a function of s…”

Section: Introductionmentioning

confidence: 99%

Distance Dependence of Angular Correlations in Dense Polymer Solutions

et al. 2010

Self Cite

View full text Add to dashboard Cite

Angular correlations in dense solutions and melts of flexible polymer chains are investigated with respect to the distance r between the bonds by comparing quantitative predictions of perturbation calculations with numerical data obtained by Monte Carlo simulation of the bond-fluctuation model. We consider both monodisperse systems and grand-canonical (Florydistributed) equilibrium polymers. Density effects are discussed as well as finite chain length corrections. The intrachain bond-bond correlation function P (r) is shown to decay as P (r) ∼ 1/r 3 for ξ ≪ r ≪ r * with ξ being the screening length of the density fluctuations and r * ∼ N 1/3 a novel length scale increasing slowly with (mean) chain length N .

show abstract

Are polymer melts “ideal”?

Cited by 14 publications

References 11 publications

Molecular dynamics study of polymer conformation as a function of concentration and solvent quality

Molecular dynamics study of polymer conformation as a function of concentration and solvent quality

Intramolecular long-range correlations in polymer melts: The segmental size distribution and its moments

Distance Dependence of Angular Correlations in Dense Polymer Solutions

Contact Info

Product

Resources

About