Swelling of asymmetric pom-pom polymers in dilute solutions

TL;DR

This study investigates how asymmetry in pom-pom polymers affects their size and shape in dilute solutions, combining analytical methods and simulations to reveal increased effective size and asymmetry characteristics.

Contribution

It provides the first comprehensive analysis of asymmetric pom-pom polymers, combining analytical and simulation approaches to quantify size, shape, and asymmetry effects.

Findings

Asymmetry increases the effective size of pom-pom polymers.

Universal size and shape characteristics depend on $f_1$ and $f_2$.

Asymmetry factor and center of mass shift serve as asymmetry indicators.

Abstract

In this paper we continue our recent analysis [K. Haydukivska et al., J. Mol. Liq., 2021, 328, 115456] of complex molecules with two branching points at both ends of the linear backbone with $f_1$ and $f_2$ side arms starting from them, known as the pom-pom polymers. Here, we analyze the asymmetric case, $f_1 \neq f_2$, by applying both the analytical approach, based on the direct polymer renormalization, and computer simulations using both dissipative particle dynamics and Monte Carlo methods. We study the role played by the molecular asymmetry of average polymer conformations, considering the infinite dilution regime and good solvent conditions.The quantitative estimates are reported for the set of universal size and shape characteristics of such molecules and for their individual branches, all the functions of $f_1$ and $f_2$. In particular, we evaluate the size ratio of the gyration radii of symmetric and asymmetric pom-pom topologies with the same molecular weight and quantitatively reveal an increase of the effective size of a molecule caused by its asymmetry. We also introduce and analyse the asymmetry factor and estimate the shift of the center of mass caused by the presence of side stars, which can serve as another characteristic of the asymmetry of pom-pom structure.