Atomistic simulation of thermal treatment effect on hydroxy-containing polyimides (HPIs) having rigid polymer backbone.

Thermal treatment of polymer has been widely used to improve mechanical and chemical stability by the physical effect such as annealing and quenching and/or the chemical reaction such as crosslinking. [1] However, it is difficult to demonstrate how thermal treatment affects the polymer structure at the atomistic and molecular levels such as configuration, conformation, glass transition temperature and free volume. In particular, if a chemical reaction occurs during the thermal treatment, the structureproperty relationship between starting and final structures become more and more complex. To address this issue, modeling based on molecular dynamics (MD) and monte carlo simulation (MC) is regarded as a powerful tool. Using molecular simulation, the various parameters related with chemical properties can be easily calculated and visualized. Also, the structural factors such as conformation and configuration studies can be specifically analyzed and intuitively demonstrated. Consequently, molecular modeling can enhance our knowledge about membrane structure and properties.[2,3] In this study, we carried out atomistic simulation to elucidate the effect of thermal treatment on the thermal rearrangement reaction (TR reaction) of hydroxy-containing polyimides (HPIs) to polybenzoxazoles (PBOs). Although polyimides (PIs) and polybenzoxazoles (PBOs) have been received much attention as engineering polymers, due to their strong mechanical and chemical stabilities, there are not so many reports due to the rigidity of their cyclic backbone structures and the resulting complexity and difficulty in simulation.[4] In addition, among the thermal treatment methods, TR reaction has one of the most complex and difficult mechanism because both physical and chemical aspects should be considered due to its high thermal treatment temperature.[5] Accordingly, through this study, we will suggest the effective way to simulate the rigid polymer such as PIs and PBOs, and show the thermal treatment effect on their structure.