Calorimetric and optical investigation of the nematic, splay-nematic, and ferroelectric nematic phases of RM734 liquid crystal

RM734 is one of the first two liquid crystal compounds reported to exhibit the ferroelectric nematic phase. At the early stage of its characterisation, a direct nematic – to – ferroelectric nematic phase transition was reported for this compound. However, subsequent studies revealed the presence of an intermediate phase between the nematic and ferroelectric nematic ones. Here, we provide additional evidence on the calorimetric signature and the optical texture of this intermediate phase, referred to as the splay-nematic phase. Next, we briefly comment on the nature of the transitions between the nematic, splay-nematic, and ferroelectric nematic phases, and the substantially different transition temperatures reported in the literature for RM734.