Abstract
Results of molecular dynamics simulations for systems with two flexible, oppositely charged polymer chains are presented. It is shown that the chains aggregate into densely packed structures. The universal properties of the formed complexes are investigated as a function of chain length and interaction strength. For weakly interacting systems, a chain length-dependent effective interaction strength is obtained which governs the initiation of the aggregation process. At intermediate interaction strengths, the formed complexes exhibit a scaling behaviour with respect to molecular weight typically for chain molecules in a bad solvent. An unusual weak dependence of the radius of gyration on the interaction strength is found in this regime. Finally, for strong interactions, tightly packed globules are obtained. The radii of gyration and the densities of the complexes are discussed.
Highlights
Aggregates between oppositely charged macromolecules play a fundamental role in technical applications and in particular in biological systems
The simulations reach beyond previous ones, since we study systematically a large range of interaction strengths and chain lengths
The effective interaction among the chains is chain-length-dependent. This is obvious from figure 1, which displays the radii of gyration for various chain lengths
Summary
Aggregates between oppositely charged macromolecules play a fundamental role in technical applications and in particular in biological systems. The aim of the simulations presented in this paper is to investigate the universal properties of aggregates formed by oppositely charged chain systems when they collapse, thereby forming compact cluster-like structures which are physically constrained to a small region in space. The simulations reach beyond previous ones, since we study systematically a large range of interaction strengths and chain lengths. The results apply to the formation of chain-pairs in many-chain systems only Such pairs form certainly in dilute systems, where the density is much smaller than the overlap concentration. In this limit, the behaviour of the solution is determined by the aggregates of two or only a few chains.
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