On the swelling properties of pom-pom polymers in dilute solutions. Part 1: symmetric case

TL;DR

This study investigates the conformational properties and swelling behavior of symmetric pom-pom polymers in dilute solutions using universal ratios, combining theoretical and simulation methods for comprehensive analysis.

Contribution

It introduces a combined theoretical and simulation approach to analyze universal shape ratios of symmetric pom-pom polymers, extending understanding beyond melt rheology to dilute solution conformations.

Findings

Theoretical and simulation results agree well for certain shape properties.

Universal ratios depend only on dimension, solvent quality, and branching topology.

The study provides detailed quantitative insights into swelling effects of pom-pom polymers.

Abstract

We consider the simplest representative of the class of multiply branched polymer macromolecules, known as a pom-pom structure. The molecule consists of a backbone linear chain terminated by two branching points with functionalities (numbers of side chains) of $f_1$ and $f_2$, respectively. In a symmetrical case, considered in the present study, one has $f_1=f_2=f$ with the total number of chains $F=2f+1$. Whereas rheological behaviour of melts of pom-pom molecules are intensively studied so far, we turn our attention towards conformational properties of such polymers in a regime of dilute solution. The universality concept, originated in the critical phenomena and in scaling properties of polymers, is used in this study. To be able to compare the outcome of the direct polymer renormalization approach with that obtained via dissipative particle dynamics simulations, we concentrated on the universal ratios of the shape characteristics. In this way the differences in the energy and length scales are eliminated and the universal ratios depend only on space dimension, solvent quality and a type of molecular branching. Such universal ratios were evaluated both for a whole molecule and for its individual branches. For some shape properties, theory and simulations are in excellent agreement, for other we found the interval of $F$ where both agree reasonably well. Combination of theoretical and simulation approaches provide thorough quantitative description of the peculiarities of swelling effects and spatial extension of pom-pom molecules and are compared with the known results for simpler molecular topologies.