Single chain elasticity and thermoelasticity of polyethylene

Abstract

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

Semiflexible macromolecules in quasi-one-dimensional confinement: Discrete versus continuous bond angles

“…1(b), and polystyrene (PS) exhibit already some local stiffness that needs to be accounted for, and many other rather stiff synthetic polymers exist. Thus, while for PE at T = 400 K, ℓ p ≈ 0.75 nm (and the length ℓ of the C-C bond is 0.15 nm) 66 and for PS corresponding literature estimates 67,68 are ℓ = 0.25 nm, ℓ p ≈ 1.0 − 1.15 nm, a comparative study of various synthetic polymers 69 has yielded estimates for ℓ p in the range from 1 nm to 42 nm, giving also evidence for the double crossover (from rods to Gaussian coils and then to swollen coils) with…”

Isometric and Isotensional Force‐Length Profiles in Polymethylene Chains

“…In thermoelastic analysis the force is split into the energy and entropy parts 19–21. The same approach can be applied to the mean force in isometric ensemble 〈 F 〉 = 〈 F 〉 U + 〈 F 〉 S .…”

“…Numerous improvements over the ideal‐chain description of chain elasticity by the FJC and WLC models are available in the low‐force region. These developments, focused primarily on the excluded volume interaction, solvent conditions, chain flexibility, etc., are based either on analytical treatments15 employing the non‐Gaussian distribution functions or on the Monte Carlo or molecular‐dynamic simulations 9,16–21. The simulations employ mostly the coarse‐grained approach owing to sufficient universality in elastic behavior of macromolecules in the low‐force region.…”

“…In the low‐force region the simulations confirm the dominance of the entropy contribution to force (owing to the large number of conformations available) over the energy contribution due to the conformation isomerization. The concrete entropy/energy partition can be deduced from the thermoelastic properties of single chains 19–21…”

Multiple Histogram Method and Static Monte Carlo Sampling

“…Two basic strategies exist to study the deformation behavior of a single polymer chain: the stress ensemble, in which one measures the elongation of a chain subjected to a stretching force, and the strain ensemble, in which one measures the internal retractive force of a chain at fixed elongation. Various Metropolis Monte Carlo [16] approaches have been used to simulate self-avoiding polymer chains using both the stress ensemble [17][18][19][20][21][22][23] and the strain ensemble. [21,[24][25][26] These Monte Carlo simulations include athermal chains and chains in good/bad solvents using different polymer models.…”