Semiflexible Macromolecules with Discrete Bond Angles Confined in Nanoslits: A Monte Carlo Test of Scaling Concepts

Abstract

Single semiflexible polymer chains confined in a planar slit geometry between parallel nonadsorbing repulsive walls a distance D apart are studied by Monte Carlo simulations of a lattice model, for the case of good solvent conditions. The polymers are modeled as self-avoiding walks on the simple cubic lattice, where every 90° kink requires a bending energy eb. For small qb = exp(−eb/kBT) the model has a large persistence length lp (given by lp ≈ 1/(4qb) in the bulk three-dimensional dilute solution, in units of the lattice spacing). Unlike the popular Kratky–Porod model of worm-like chains, this model takes both excluded volume into account and approximates the fact that bond angles between subsequent carbon–carbon bonds of real chains are (almost) restricted to large nonzero values, and the persistence length is controlled by torsional potentials. So the typical local conformation in the model is a straight sequence of (on average) lp bonds (roughly corresponding e.g. to an all-trans sequence of an alkan...