Molecular dynamics simulation of the thermo-mechanical properties of helicene-siloxane based alternating co-polymers

Many applications in materials science rely on thermal and mechanical stability of polymeric materials. In most cases, pure polymers by themselves do not have the necessary thermo-mechanical properties desirable for basic functionality. On the other hand, polymer-based composite materials may impart enhanced thermal, mechanical and viscoelastic properties as compared to the pure polymers. Helicenes are ortho fused polycyclic aromatic compounds which are expected to provide unique multi-functionality (high glass-transition temperature (T_g), high-temperature stability , strain sensing, dichroism, non-linear optics, etc.) when present as part of a polymeric backbone. In this work, linear alternating helicene-siloxane copolymers are obtained through a process mimicking experimental step-growth polymerization starting from a mixture of individual helicene and siloxane molecules using the LAMMPS reactor module. Various properties of the co-polymers are investigated via all-atom molecular dynamics simulations. Specifically, results will be presented to highlight the influence of molecular weight as well as helicene and siloxane content on glass transition temperature(T_g), density, coefficient of thermal expansion, and local ordering of helicenes.