Conformational and static properties of tagged chains in solvents: effect of chain connectivity in solvent molecules

TL;DR

This study uses molecular dynamics simulations to compare how chain connectivity in solvents influences the conformational and static properties of tagged polymer chains, revealing effects on chain compression, distribution, and pore structure.

Contribution

It demonstrates the impact of solvent chain connectivity on polymer chain behavior, highlighting differences in compression, distribution, and pore size compared to bead solvents.

Findings

Chain confinement causes chain compression, more so in chain solvents.

Distribution of chain sizes remains unchanged across solvent densities.

Increased solvent density leads to a bimodal bond angle distribution.

Abstract

Polymer chains immersed in different solvent molecules exhibit diverse properties due to multiple spatiotemporal scales and complex interactions. Using molecular dynamics simulations, we study the conformational and static properties of tagged chains in different solvent molecules. Two types of solvent molecules were examined: one type consisted of chain molecules connected by bonds, while the other type consisted of individual bead molecules without any bonds. The only difference between the two solvent molecules lay in the chain connectivity. Our results show a compression of the tagged chains with the addition of bead or chain molecules. Chain molecule confinement induces a stronger compression compared to bead molecule confinement. In chain solvent molecules, the tagged chain's radius of gyration reached a minimum at a monomer volume fraction of $\sim0.3$. Notably, the probability distributions of chain size remain unchanged at different solvent densities, irrespective of whether the solvent consists of beads or polymers. Furthermore, as solvent density increases, a crossover from a unimodal to a bimodal distribution of bond angles is observed, indicating the presence of both compressed and expanded regions within the chain. The effective monomer-solvent interaction is obtained by calculating the partial radial distribution function and the potential of the mean force. In chain solvent, the correlation hole effect results in a reduced number of nearest neighbors around tagged monomers compared to bead solvents. The calculation of pore size distribution reveals that the solvent nonhomogeneity induced by chain connectivity leads to a broader distribution of pore sizes and larger pore dimensions at low volume fractions. These findings provide a deeper understanding of the conformational behavior of polymer chains in different solvent environments.