The structure of star-branched copolymers. A Monte Carlo study

A coarse-grained model of a many-arm star-branched polymer chain has been studied. The chains were flexible heteropolymers built of two kinds of united atoms (segments) – hydrophobic and hydrophilic. The positions of segments were restricted to the vertices of a [310] hybrid lattice. The force field consisted of the softened excluded volume and the long-distance potential between a pair of non-bonded segments. The properties of these macromolecular models were studied in a wide range of temperatures from random coil to dense globule states. Monte Carlo simulations were performed using an algorithm based on the chain’s local changes of conformation and employing the Replica Exchange technique. The influence of the polymer length, the sequence of segments in the chain and the temperature on the dimension and the structure of chains have been studied. It has been shown that the process of the heteropolymer chain collapse to low-temperature structures is a complicated phenomenon and a possible explanation of this behavior has been discussed.