GEMOX: A simple and efficient strategy for the generation of polymer molecular models compatible with X-ray diffraction data

A computational method based on a corrected grid search algorithm has been developed to help in the conformational analysis of crystalline polymers by X-ray diffraction. The program was designed upon the difficulty of taking into account all the molecular arrangements that are initially compatible with the experimental diffraction data of polymers, in particular when these consist of chemical repeating units with a wide accessible conformational space. The strategy presented here has been incorporated into a computer program named GEMOX. First, all the models fitting the experimentally determined axial repeat of the chain and having the helical symmetry known for the polymer are rapidly created by computing their atomic coordinates. Secondly, sterically hindered conformations are discarded using force-field energy criteria. For this, a potential energy function containing both non-bonded and torsional terms has been incorporated in the program. The ability of the method to provide a complete survey of the reasonable models for a given system was tested for three well characterized polymers, all of them displaying a complex conformational behaviour. Copyright (C) 1996 Elsevier Science Ltd.