arXiv subjects

Ostap Kalyuzhnyi

Publications and source records attributed to Ostap Kalyuzhnyi.

4 recordsLinked to original sources

arXiv2022

Swelling of asymmetric pom-pom polymers in dilute solutions

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.

cond-mat.soft↗

arXiv2020

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

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.

cond-mat.soft↗

arXiv2019

Universal size and shape ratios for arms in star-branched polymers: theory and mesoscopic simulations

Star polymer undergoes a transformation from a group of loosely coupled chains at low number of arms to a dense hairy colloid at their high number. This change affects solubility, aggregation and rheological behavior and is of much practical interest. We study the range of size and shape properties of the star molecule and of its individual arms upon this transformation. Theoretical calculations are based on a continuous chain model and are performed in the first order in $ε=4-d$. Computer simulations are done by the dissipative particle dynamics and in part by Monte Carlo method and the results demonstrate very good agreement with the selected set of properties known from the previous simulations. Theory and simulations provide qualitatively similar trends upon increase of the number of arms, but higher order of approximation is required in a theory to achieve a good quantitative agreement.

cond-mat.soft↗

arXiv2016

Universal shape characteristics for the mesoscopic polymer chain via dissipative particle dynamics

In this paper we study the shape characteristics of a polymer chain in a good solvent using a mesoscopic level of modelling. The dissipative particle dynamics simulations are performed in the $3D$ space at a range of chain lengths $N$. The scaling laws for the end-to-end distance and gyration radius are examined first and found to hold for $N\geq 10$ yielding reasonably accurate value for the Flory exponent $ν$. Within the same interval of chain lengths, the asphericity, prolateness, size ratio and other shape characteristics of the chain are found to become independent of $N$. Their mean values are found to agree reasonably well with the respective theoretical results and lattice Monte Carlo simulations. Broad probability distributions for the shape characteristics are found resembling in form the results of lattice Monte Carlo simulations. By means of analytic fitting of these distributions the most probable values for the shape characteristics are found to supplement their mean values.

cond-mat.soft↗