Compaction of grafted wormlike chains under variable confinement

Abstract

We study the mean molecular shape features for a model of wormlike chains with variable persistence length and nonbonded pair interactions. The chains are modelled as end-grafted and confined within an infinite slab with variable thickness. By using two independent shape properties (mean size and the complexity of chain entanglements), as well as a reference model with no attractive interactions (the self-avoiding walk), we propose an unbiased criterion to detect the formation of compact configurations. This process of compaction resembles qualitatively the onset of a “collapse transition” in a finite-size polymer. The method can be used even for short and medium-size chains, where scaling arguments are not applicable. We show that compaction occurs both for free mushrooms and strongly-confined chains. Moreover, the onset of compaction appears to depend little on the level of confinement. We find the same characteristic behaviour for either flexible or stiff chains, or for chains with interactions covering the range from good to poor solvent.