A Modeling and Simulation Method for High-Performance Amorphous/Semi-Crystalline Oriented Fibers: Structural Design and Performance Prediction

Molecular structure design based on molecular simulation is proving to be an effective method for enhancing the mechanical properties of polymers. However, the conventional fully-crystalline and isotropic models fall short in accurate structural design and performance prediction of high-performance amorphous/semi-crystalline oriented fibers. Herein, uniaxially oriented amorphous/semi-crystalline models established through the NPT ensemble with applied stresses were presented, demonstrating closer agreement with the density and tensile strength of actual high-performance polymer fibers compared to conventional models. Taking aramid fibers for instance, six heterocyclic units were introduced to design heterocyclic aramids with varying strengths of π-π interactions and hydrogen bonding, and the novel models were employed to deeply explore the quantitative relationship between molecular interaction and orientation, as well as their quantitative effects on mechanical properties. It revealed that π-π interactions impose greater restrictions on orientation during the hot-drawing simulation process than hydrogen bonding, and both interactions and orientation play equally important roles in determining tensile strength. Ultimately, the optimal structure was identified as 2-(2-hydroxy-4-aminophenyl)-5(6)-aminobenzimidazole, which exhibited strong hydrogen bonds, high orientation, and excellent tensile strength. This research provides an efficient and feasible simulation method for designing of high-performance amorphous/semi-crystalline oriented fibers.