Pressure studies on phase transitions in 4-alkoxyphenyl-4’-nitrobenzoyloxybenzoates

We have studied the effect of high pressure on the phase transitions in the seventh to tenth homologs of 4-alkoxyphenly-4’-nitrobenzoyloxybenzoates (DB.kO.${\mathrm{NO}}_2$). While pressure does not induce any new phases in k=7 or 8, it has a dramatic effect on k=10: triply reentrant behavior is seen over a narrow range of pressure, the sequence of transitions being the same as that observed in k=9 or DB.9O.${\mathrm{NO}}_2$ at atmospheric pressure. This is the first instance of pressure-induced multiply reentrant behavior in a single-component system. The observed sensitivity of the multiply reentrant behavior to molecular chain length and pressure is according to the predictions of the frustrated spin-gas model of polar liquid crystals.