Effect of the mesogenic type of attachment and composition on the structural and viscoelastic behavior of side-chain liquid crystal polymer systems

Side-chain liquid crystal polymers (SCLCPs) consist of a flexible backbone with mesogenic units attached in an end-on or a side-on configuration as pendant groups via flexible spacers. These molecules have potential applications in areas requiring controllable deformations. At high enough temperatures, entropic effects dominate, and the polymer chains approach a random walk configuration. In contrast, at lower temperatures, the liquid crystal (LC) groups can form ordered phases. We conduct coarse-grained molecular dynamics simulations of SCLCP systems with purely end-on and purely side-on groups, and also copolymers with both LC types at a variety of compositions. For some compositions, the transition temperature of copolymers lies below that of both respective SCLCPs with only one LC type, which we attribute to the disruption of the orientational and positional order of the crystalline mesophases when two different LC types are attached to the same polymer backbone. Also, we have observed that this non-monotonic behavior for the transition temperature is extended to the relaxation dynamics of the systems. This work provides molecular insights into the origin and mechanisms behind the non-monotonic trends observed in the structural and viscoelastic behavior of the SCLCP systems.