Chain Conformation and Packing Structure of Interlocked Ring Polymers in Semidilute Solutions: The Role of Topological Catenation

Extensive molecular dynamics simulations of the Kremer–Grest model have been carried out to explore the static properties (e.g., conformation statistics and chain packing structures) of interlocked ring polymers ([n]catenanes, i.e., each interlocked ring polymer is composed of n concatenated rings) with varying n and fixed chain length N = 1200 in semidilute solutions, aiming to identify the specific role of the catenation topology therein. To this end, therefore, [n]bonded-ring polymers, the counterparts of [n]catenanes, have been considered as well, where rings are covalently bonded together along the [n]bonded-ring polymer. Our computational study indicates that the equation ⟨Rg2(ϕ)⟩⟨Rg2(0)⟩=[1+α(ϕϕ*)]β, which holds for both linear and ring polymer solutions, may no longer be generally valid for the case of interlocked ring polymers in solutions. Nevertheless, the scaling law, ⟨Rg2⟩ ∼ ϕβ, still holds in semidilute solutions for both cases of [n]catenanes and [n]bonded-ring polymers. Importantly, the scaling exponent β for the case of [n]catenanes becomes n-dependent, i.e., β = β(n), and specifically, the β value decreases with increasing n. In contrast, β remains approximately constant for [n]bonded-ring polymers. Furthermore, catenation topology also induces a difference in chain packing structures between the interlocked ring polymers and bonded-rings in semidilute solutions. It is revealed that [n]catenanes are pronouncedly more segregated compared to those of [n]bonded-rings in semidilute solutions.