Multiscale modelling of mesoscopic behaviour in soft matter systems

Soft matter modelling has a wide range of applications, such as polymer additive manufacturing, organics electronics, and biomolecular engineering. Many physical properties and phenomena of soft matter are determined by interactions and processes at a wide range of length and time scales. Therefore, it is challenging for theoretical models to simulate processes involving features from multiple scales. To reach the mesoscopic scales for soft matter behaviour, coarse-grained models have been developed to accelerate the atomistic models by projecting out the relevant degrees of freedom, allowing coverage of a wider range of scales. However, due to the lack of a formalism to capture the dynamics and anisotropy of the system, conventional coarse-grained model shows significant errors in dynamical properties and inconsistent soft matter behaviour.

In this thesis, a generalised systematic formalism for coarse-graining is presented. The Mori-Zwanzig formalism provides a dynamically-guided projection to construct a mesoscopic system directly from the underlying microscopic system. Moreover, the Gay-Berne functional is introduced to describe the anisotropic effect of the pairwise interactions at mesoscopic level. ... mehrThe performance of the model is demonstrated by comparing it to other coarse-grained models using benzene as an example, which shows significant improvement in both static and dynamical properties. For application, crystallization of pentacene is studied by treating pentacene molecule as ellipsoidal particle. Furthermore, a modified atomistic model and a modified continuum model are employed to simulate mesosopic behaviour of polymers in electrospinning and electro-optical poling, demonstrating mesoscopic modelling from the atomistic and continuum limits.