Effects of Relative Rigidities of Backbone and Arms on Conformational and Dynamical Characteristics of Branched Ring Polymer in Shear Flow

Abstract

We investigate how the relative rigidities of the backbone and arms influence the conformational and dynamical properties of branched ring polymers (BRPs) under steady shear flow, using a hybrid mesoscale simulation approach that combines multiparticle collision dynamics with standard molecular dynamics. Our results reveal that both the conformational characteristics and the dynamic behavior of the BRP are strongly dependent on the relative rigidities of the backbone and arms and especially on the latter. As the shear rate increases, for the BRP with a flexible backbone and flexible arms, it first tends toward a more prolate shape, then toward a more spherically symmetric shape, and finally reverts to a more prolate shape. Meanwhile, its dynamic behavior evolves from random alternation between tumbling (TB) and tank-treading (TT) motions (TB-dominated) to stable TB motion and finally to a coexistence of both motions. For the BRP with a stiff backbone and flexible arms, its conformational evolution resembles that of the BRP with a flexible backbone and flexible arms. In contrast, it undergoes TB motion exclusively. For the BRP with a flexible backbone and stiff arms, it first tends toward a more prolate shape and then transitions to a more spherically symmetric shape. Meanwhile, its dynamic behavior evolves from random alternation between TB and TT motions (TT-dominated) to almost exclusive TT motion. For the BRP with a stiff backbone and stiff arms, it first tends toward a more prolate shape, then transitions to a more spherically symmetric shape, and finally shifts toward a more oblate shape. Meanwhile, its dynamic behavior evolves from predominant TB motion with occasional TT motion to predominant TT motion with occasional TB motion.