A molecular theory including hard rod interactions of liquid crystalline phases exhibited by highly polar compounds

We extend our molecular mean field model of highly polar compounds to inclu de hard rod interactions to develop a hybrid model. The latter interactions are restricted to second virial terms, following a method developed by Kod a and Kimura. This allows us to calculate pressure-temperature phase diagra ms. Depending on the model parameters used, the phase diagrams exhibit the following features: nematic-nematic phase transition, bounded SmA(d) region , double reentrance, reentrant nematic lake surrounded by the smectic A pha se (the reentrant nematic lake merging with the main nematic sea) as well a s the possibility of quadruple reentrance. We compare the calculated phase diagrams with the available experimental data.