Modelling the structural and physicomechanical properties of substituted poly(p-phenylene)s using molecular mechanical and molecular orbital methods

Conducting polymers are important technological materials that are finding increasing use in batteries and display devices. The conformation and packing of these polymers in the amorphous glassy state are poorly understood, despite the fact that they dictate their most important physical and mechanical properties. The processing of currently known conducting polymers is difficult and there is a strong incentive to increase their processability through functionalization. Developing an ability to predict the structure and structure-property relations of conducting polymers in the bulk will help with the design of new structures that combine processability with favourable electronic properties and facilitate their use in future high-technology applications. In this work, we concentrate on substituted poly(p-phenylene)s. Detailed atomistic molecular models have been developed with the help of molecular mechanics and semi-empirical quantum mechanical calculations using Cerius and MOPAC V6.0 program packages and structural, volumetric, and mechanical properties, e.g. geometrical values, densities, have been calculated by simulations on these models. The results from both methods have been compared with simulated and experimental data and conclusions have been drawn on the methodology and the approximations used. This study was used to compare with results obtained on unsubstituted poly(p-phenylene)s carried out earlier and to continue to develop our methodology for calculating structure, physical and mechanical properties that will be generally applicable to conductive polymers. (C) 2002 Published by Elsevier Science Ltd.