Modelling of structural and physicomechanical properties of poly-paraphenylene using molecular orbital and molecular mechanical methods

Conducting polymers are important technological materials that are finding increasing use in batteries and display devices. The conformation and packi ng of these polymers in the amorphous glassy state are poorly understood, d espite the fact that they dictate their most important physical and mechani cal properties. The processing of currently known conducting polymers is di fficult and there is a strong incentive to increase their processability th rough blending with other polymers or functionalisation. Developing an abil ity to predict the structure and structure-property relations of conducting polymers in the bulk will help with the design of new structures that comb ine processability with favourable electronic properties and facilitate the ir use in present-day high-technology applications. In this work, we will c oncentrate on a very important conductive polymer: poly(p-phenylene). Detai led atomistic molecular models have been developed with the help of molecul ar mechanics and semi-empirical quantum mechanical calculations using Ceriu s and MOPAC program packages and structural, volumetric, and mechanical pro perties, e.g., geometrical values, density, have been calculated by simulat ions on these models. The results from both methods have been compared with simulated and experimental data and conclusions have been drawn on the met hodology and the approximations used. This study was used to validate the e xisting molecular simulation software; to produce force fields, appropriate for the reliable molecular simulation of chemically complex polymer system s; and to develop a new methodology for calculating structure, physical and mechanical properties that will be generally applicable to conductive poly mers. (C) 2000 Elsevier Science S.A. All rights reserved.