Influence of the electrostatic interactions on thermophysical properties of polyimides: Molecular‐dynamics simulations

Revealing the way of how modification of the chemical structure of a polymer affects its macroscopic physical properties offers an opportunity to develop novel polymer materials with pre‐defined characteristics. To address this problem two thermoplastic polyimides, ULTEM™ and EXTEM™, were simulated with small difference in chemical structures of monomer units, namely, the phenyl ring in ULTEM™ was replaced by the diphenylsulphone group in EXTEM™. It is shown that such a small modification results in a drastic difference of the thermal properties: the glass transition temperature of EXTEM™ is higher than that of ULTEM™. Our molecular‐dynamics simulations clearly demonstrated that it is the electrostatic interactions that are responsible for the observed difference in thermal properties of ULTEM™ and EXTEM™: large partial charges of the sulphone group in the EXTEM™ lead to strong dipole–dipole intra‐ and intermolecular interactions and correspondingly to an elevated glass transition temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52 , 640–646