Molecular weight effects on interfacial properties of linear and ring polymer melts: A molecular dynamics study

Abstract

Using molecular dynamics simulations, we study and compare the pressure, P, and the surface tension, γ, of linear chains and of ring polymers at the hard walls confining both melts into a slit. We examine the dependence of P and γ on the length (i.e., molecular weight) N of the macromolecules. For linear chains, we find that both pressure and surface tension are inversely proportional to the chain length, P(N)-P(N→∞)∝N,γ(N)-γ(N→∞)∝N, irrespective of whether the confining planes attract or repel the monomers. In contrast, for melts comprised of cyclic (ring) polymers, neither the pressure nor the surface tension is found to depend on molecular weight N for both kinds of wall-monomer interactions. While other structural properties as, e.g., the probability distributions of trains and loops at impenetrable walls appear quantitatively indistinguishable, we observe an amazing dissimilarity in the probability to find a chain end or a tagged monomer of a ring at a given distance from the wall in both kinds of polymeric melts. In particular, we demonstrate that the conformational equivalence of linear chains in a confined melt to a single chain under conditions of critical adsorption to a planar surface, established two decades ago, does also hold for ring polymers in a melt of linear chains. This analogy does not hold, however, for linear and ring chains in a confined melt of ring chains.

Capillary Filling of Polymer Chains in Nanopores

“…We show the simulation results of the surface tension γ, viscosity η, and contact angle θ of the polymer in Figures , , and , respectively. The variation of surface tension γ with molecular weight M for polymer melt follows the relation |γ – γ ∞ | ∝ M –1 , which has been confirmed by many experiments, simulations, and theory. , Our result is consistent with this relation as shown in Figure b, where N = M / M 0 and M 0 is the molar mass of the repeat unit.…”

Radial Distribution Function Analysis of the Polyamide Thin Film Composite formation using Trimesoyl Chloride and Piperazine

“…Moreover, the system process and error of the actual process can be firstly estimated using the simulation which assists to reduce the time and cost [12]. MD is known for its accurate data which compatible with the results obtained from the actual process [13][14][15].…”

Molecular Weight Dependence of Surface Tension of Poly(ethylene oxide) Solution

“…19 Molecular dynamics simulations were also used to verify the role of the terminal segments. 20 On the other hand, based on the early work of Cahn and Hilliard, 21 the variation of the melt density with molecular weight was considered as the primary contribution to the molecular weight dependence of surface tension. 22 This was supported by studies that separated the contribution of the chain-end segregation and the density variation.…”