Chain Molecules at High Densities at Interfaces

Abstract

We have reviewed the general principles of interfacial constraint on highly concentrated polymers near sharp interfaces. First, chains are constrained by their inability to penetrate the boundary. Second, at high concentration, polymers are also constrained by interactions with neighboring chains. Third, one additional constraint depends on the chain length: (a) for long chains, a symmetry condition arises from the indistinguishability of segments k and k + 1, whereas (b) for shorter molecules, wherein the segments are distinguishable, the length of the chains is fixed. Subject to these restraints, chains at equilibrium will be configured to maximize their entropy, and hence their configurational disorder. The physical properties of chains at interfaces are often quite different from those of bulk polymers. In most such systems, the conformational ordering is dissipated within only 5-10 A from the interface, but some physical properties depend on effects that are propagated over much longer distances. The currently available theory is found to be in quite good general agreement with a large number of conformational and mixing properties of polymers at interfaces, in semicrystalline polymers, in alkane crystals, in stationary phases used in reversed-phase liquid chromatography, and in amphiphilic aggregates including bilayer membranes and micelles.

Biological and synthetic membranes: What can be learned from a coarse-grained description?

“…Differences between these methods are mostly technical. Dill et al [ 267,268] and Scheutjens and co-workers [ 269] use a lattice to describe both chain conformations as well as molecular field configurations, which can be treated with efficient transfer matrix methods originally proposed by Kramers and Wannier for solving the Ising model. Ben-Shaul et al [ 270,271,272,273] enumerate a very large set of the most probable chain configurations off-lattice and use iterative techniques to reach self-consistency.…”

“…Ben-Shaul et al [ 270,271,272,273] enumerate a very large set of the most probable chain configurations off-lattice and use iterative techniques to reach self-consistency. For a more detailed exposition of these ideas we refer the reader to excellent reviews of these works [ 268,270].…”

The effect of chain density on the frictional behavior of surfaces modified with alkylsiloxanes and immersed in n-alcohols

“…As discussed elsewhere, 12 solvent partitioning may be controlled by the distribution of free volume in the film 43 or partitioning may occur by insertion of long-chain solvent molecules into defect sites. 44 If free-volume limited partitioning is the dominant mechanism, an increase in the extent of solvent partitioning should cause to decrease, just like the relaxation time and the glass transition temperature of an amorphous polymer decrease when the polymer is exposed to a plasticizer.…”

Model for the structure of the lipid bilayer.

“…Much of the recent theoretical work on lipid structure has been based on either simplified approaches, such as the lattice (11) and mean-field (12)(13)(14) approximations, or on computationally intensive molecular dynamics (15,16) and Monte Carlo (17) simulation methods. In lattice theories, the configurations for a system composed of a set of chain molecules, each consisting of connected segments, are generated on a lattice of specified symmetry.…”