A united atom model for polyurea elastomers
Minghao Liu, Jay Oswald
Arizona State University
Elastomers such as polyurea and polyurethanes are a highly versatile class of copolymers used in coatings, armors, and composites for their high toughness, low density, and capability to dissipate energy from ballistic impacts and blast loading. The versatility of these polymeric materials arises from the ability to alter their microstructure by modifying their chemical structure, concentration and polydispersity of their constituent units, and processing conditions. However, the wide range of length and time scales over which the molecular mechanisms that govern material structure and properties operate pose a formidable challenge for molecular-scale simulations. To address this challenge, we propose a systematic approach for generating united atom (UA) models of elastomers. The method utilizes the iterative Boltzmann inversion (IBI) method to obtain the effective pair potentials for each type of super-atom. To deal with an UA model that results in many more types of super-atoms typically encountered in systematic coarse-graining, new techniques for automating IBI method are discussed. To illustrate the applicability of the methods developed, a UA model for polyurea will be presented along with a comparison of physical properties calculated by both atomistic and UA simulations.