Using Langevin simulations, we find that simple "generic" bead-and-spring homopolymer chains in a sufficiently bad solvent spontaneously develop helical order during the process of collapsing from an initially stretched conformation. The helix formation is initiated by the unstable modes of the straight chain, which drive the system towards a long-lived metastable transient state. The effect is most pronounced if hydrodynamic interactions are screened.

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.

No abstract

The phase behavior of a flexible star polymer chain in good solvent near an attractive surface is investigated by multicanonical Monte Carlo simulations where the specific heat, the parallel and the perpendicular components of the gyration tensor, and the fraction of adsorbed monomers are computed. Temperature–surface attraction strength pseudo‐phase diagrams are constructed for three chain lengths (N = 31, 41, 61) with three numbers of arms (f = 3, 4, 6). The star polymer chain adopts a desorbed expanded conformation for high temperatures and low surface attraction strength. With decreasing temperature and for sufficient surface attraction strength, the star polymer chain undergoes a transition from 3D to a 2D structure. At low temperatures, the chain is mostly adsorbed for low surface attraction strength and adopts a two‐layer arrangement at high values of the latter. In this context, it is also found that the phase behavior of flexible star polymer chains in good solvent near an attractive surface is affected by the number of arms f and that a star polymer chain with a high number of arms is necessary for a precise classification of all intermediate pseudo phases.