Nonlinear mechanics of thermoreversibly associating dendrimer glasses

Simulation Study of Process-Controlled Supramolecular Block Copolymer Phase Separation with Reversible Reaction Algorithm

A supramolecular diblock copolymer formed by reversible bonds between the two blocks shows a rich microphase separation behavior and has great application potential in stimuli-responsive materials. We propose a novel method to describe supramolecular reactions in dissipative particle dynamics, which includes a reversible reaction to accurately reproduce the strength, saturation, and dynamic properties of the reversible bonds in the simulations. The thermodynamic properties and dynamic processes of the supramolecular diblock copolymer melts in both equilibrium and non-equilibrium states were studied using this method. The simulation results show that the method can faithfully characterize phase behaviors and dynamic properties of supramolecular diblock copolymer melts, especially in a non-equilibrium state, which provides a novel tool to unveil self-assembly mechanism and describe the properties of supramolecular block copolymers.

Dynamics and reaction kinetics of coarse-grained bulk vitrimers: a molecular dynamics study

Vitrimers with dynamic covalent bonds make thermosetting materials plastic, recyclable and self-repairing, and have broad application prospects. However, due to the complex composition of vitrimers and the dynamic bond exchange reactions (BERs), the mechanism behind their unique dynamic behavior is not fully understood. We used the hybrid molecular dynamics-Monte Carlo (MD-MC) algorithm to establish a molecular dynamics model that can accurately reflect BERs, and reveal the intrinsic mechanism of the dynamic behavior of the vitrimer system. The simulation results show that BERs change the diffusion mode of the vitrimer's constituent molecules, which in turn affects the BER and other relaxation dynamics. This provides a theoretical basis and a specific method for the rational design of the rheological properties of vitrimers.

Theory of wavelet-based coarse-graining hierarchies for molecular dynamics

We present a multiresolution approach to compressing the degrees of freedom and potentials associated with molecular dynamics, such as the bond potentials. The approach suggests a systematic way to accelerate large-scale molecular simulations with more than two levels of coarse graining, particularly applications of polymeric materials. In particular, we derive explicit models for (arbitrarily large) linear (homo)polymers and iterative methods to compute large-scale wavelet decompositions from fragment solutions. This approach does not require explicit preparation of atomistic-to-coarse-grained mappings, but instead uses the theory of diffusion wavelets for graph Laplacians to develop system-specific mappings. Our methodology leads to a hierarchy of system-specific coarse-grained degrees of freedom that provides a conceptually clear and mathematically rigorous framework for modeling chemical systems at relevant model scales. The approach is capable of automatically generating as many coarse-grained model scales as necessary, that is, to go beyond the two scales in conventional coarse-grained strategies; furthermore, the wavelet-based coarse-grained models explicitly link time and length scales. Furthermore, a straightforward method for the reintroduction of omitted degrees of freedom is presented, which plays a major role in maintaining model fidelity in long-time simulations and in capturing emergent behaviors.