Mesogenic properties of chiral compounds derived from 2 (S)-[2(S)-ethylhexyloxy]propionic acid and its (S, R)-diastereomer

Two acids, 2(S)-[2(S)-ethylhexyloxy]propionic acid and 2( S)-[ 2( R)-ethylhexyloxy] propionic acid, were used as the chiral building block for the preparation of four liquid crystals 5, 6, 7 and 8. The diastereomers of the biphenyl ring system, 5 and 6, possess the phase sequence I-N*-SmC*-Cr1-Cr2, while the diastereomers of the naphthalene ring system, 7 and 8, exhibit the sequence I-SmA-SmC*-Cr. The temperature ranges of the SmC* phase for 5 and 6 are wider than those for 7 and 8; the phase transition temperatures of the SmC* phase for 7 and 8 are lower than those for 5 and 6. In the case of the diastereomers of naphthalene ring system, the larger the size of the lateral substituent at the second chiral centre, i.e. ethyl or methyl group, the wider the temperature range of the SmC* phase.