(525h) Modeling Thermosetting Polymers with Hierarchical Nanostructure

Block copolymers self-assemble into a variety of morphologies that can serve as atomic-scale templates for the creation of nanostructured metals or other classes of polymers, such as high-performance thermosets. These nanonetworks have unique mechanical and transport properties, allowing them to function as ultralight structural materials and molecular sieves. In this work, a molecular modeling protocol was developed to model the dynamic polymerization of thermosetting resins into complex nanoscale architectures. The protocol relies on several recently added features of REACTER, a versatile method for modeling chemical reactions in classical molecular dynamics simulations. To demonstrate the formation of a complex phase, the polymerization of a high-temperature resin is constrained to regions of 3D space based on the isosurface of a gyroid, a triply periodic minimal surface. Morphologies of a simpler diamond lattice are also created using the same resin. Large-scale atomistic models (one million atoms) are used to generate periodic structures with lattice constants >40 nm, approaching those observed experimentally. Mechanical properties, including ultimate strength and elastic and bulk moduli, are calculated with respect to the porosity and type of lattice, and the amount of plastic deformation as a function of strain is quantified. Finally, the diffusive transport of water and hydrogen within the open channels of these nanoscale lattices is measured via molecular dynamics. The computational protocol developed is broadly applicable to obtaining atomistic insight into the mechanical and transport properties of nanoscale functional metamaterials.