Combinatory usage of X-ray and neutron diffraction techniques for the refined structure analysis of polymer crystals: From hydrogen atoms to bonded electron density distribution

In order to predict the physical property of polymers, we need to know the atomic coordinates including hydrogen atoms as accurately as possible. However, polymer samples give us limited number of broad X-ray reflections in general. In order to improve this problem, we have made many efforts to collect the X-ray diffraction data as accurate as possible. In this paper, we report the structure analysis including the extraction of hydrogen/deuterium atomic positions for the oriented polyoxymethylene by the combination of X-ray diffraction method with neutron diffraction method. In such a cases of polydiacetylene giant single crystal the bonded electron density distribution was evaluated along the skeletal chain by the so-called X-N method based on the wide-angle X-ray diffraction data and the wide-angle neutron diffraction data.