We now focus on structural variations, highlighting how changes in molecular structure affect the transition temperatures of each material. We start by considering derivatives of RM230, purely as this was the first reported NF material that we are aware of, albeit assigned as an "unknown nematic" (NX) at the time. Confounding our initial expectations, the presence of longer terminal chains eliminates the NF phase, yet shortening the terminal chain to methoxy (to give RM734) gives a large (~ 50 °C) enhancement to TN F -N. A bulky lateral group is essential for the formation of the NF phase in the RM-type materials; the group does not simply inhibit crystallisation, and removal of the lateral group decreases TN F -N by over 100 °C. A few variants of RM230 with alternate polar units were synthesised; incorporation of fluorine ortho to the terminal nitro group boosts TN F -N by over 30 °C.