I have recorded a single crystal XRD for N-pentylcarbazole-linked moiety. I have maintained -180 °C still I ended up with some disorder in alkyl chain. How can I fix this?
Disorder can be static or dynamic. It is well possible that at -180°C it is already static, but the driving force for ordering is still positive. Then you have no chance. It is also possible, that upon cooling ordering occured but the ordered domains and/or the associated superstructure reflections are to weak to be detected under your measurement conditions.