A simple molecular model for N-SmA(d)-N-dRe-N-1Re-SmA(1) phase sequence inhighly polar compounds

Our earlier model of re-entrant liquid crystalline phases exhibited by high ly polar compounds, in which the mutual orientation of near-neighbour molec ules can change from an antiparallel to a parallel configuration, has been extended to include both nematic and smectic interactions. We show that, as the McMillan parameter alpha is decreased, the SmA(d)-SmA(1) line goes ove r to the Sm4(d)-N-1Re line, finally becoming the N-dRe-N-1Re transition lin e, the latter ending in a critical point. This sequence is in agreement wit h the predictions of Frost's Landau model as well as with an experimental r esult. The phase sequence N-SmA(d)-N-dRe-N-1Re-SmA(1) is obtained on coolin g for a range of alpha(A) values.