A coarse-grained simulation study of mesophase formation in a series of rod-coil multiblock copolymers

The mesophase behaviour of a rod-coil multiblock copolymer is assessed by means of a new soft-core simulation model, which is suitable for the simulation of combinations of isotropic and anisotropic particles. The simulations demonstrate the presence of isotropic melt, micelles, lamellar, nematic and gyroid phases, with ordered phases able to grow spontaneously from the isotropic melt. The influence of increasing the length of the rigid rod-component of the polymer is studied, with mesophase stability enhanced by increases in rod length. Increased nematic phase stability is demonstrated also as the length of rod component is increased. For longer rods (smaller fraction of coils) the models show evidence of metastable chevron-like structures that initially form on cooling from the polymer melt. These are eventually lost in favour of true lamellar ordering over long annealing runs. The structure of molecules within the phases formed is also assessed. Chains in the lamellar phase are shown to produce both bridging and loop behaviour, with the latter preferred slightly. Simulations at a low occupied volume fraction, corresponding to self-assembly in solution, demonstrate the formation of a structurally ordered nanowire.