Beyond small molecule crystals, polymer crystal systems may also exhibit planar disorder in which streaking has been previously observed . This behaviour often falls under the wider umbrella of mosaicity and may be regarded as a barrier to structure solution. The extended application of similar electron diffraction techniques used in this work may help to understand the nanoscale structure of larger complexes , i.e. in cases where the polytypism affects any crystal large enough for single crystal X-ray diffraction. Finally, further investigation to understand the preferred tendencies of these planar crystal systems could be undertaken using computational Crystal Structure Prediction methods such as Density Functional Theory or Ab Initio Random Structure Searching . It would also be interesting to understand how this stacking behaviour changes in the hydrated forms of the compounds . This is a topic of extensive interest given the role of nucleic acid interaction in stability and conformational variability of biological systems. Within biological systems, most interactions between nucleic acid molecules occur in the presence of solvent molecules, and the successful competition of water may significantly change intermolecular hydrogen bonding and therefore stacking variability .