ELECTRONIC-STRUCTURE AND CONFORMATION OF POLYMERS FROM CLUSTER MOLECULAR-ORBITAL AND MOLECULAR MECHANICS CALCULATIONS - POLYIMIDE

Full geometry optimizations using molecular mechanics and the quantum chemical AM 1 methodhave been carried out to determine the minimum energy conformation of pyromellitic dianhydride-oxydianiline polyimide (PMDA-ODA PI). The phenyl-imide twist angle for this compound was determined to be ~30°. These computations also provided a quantitative determination of the energy gap (7 eV), electron affinity (-2 eV), and ionization potential (8.97 eV). Computations on the PMDA-ODA PI radical anion provided an estimate of the “hopping” barrier for an electron to hop from one chain to another (3.2 eV), the mechanism believed responsible for photoconduction. Moreover, the use of qualitative molecular orbital theory (QMOT) arguments provided an interpretation of these results in a simple molecular orbital framework. © 1990, American Chemical Society. All rights reserved.