Induction of smectic layering in nematic liquid crystals using immiscible components III. The effect of lateral n-alkanoyl substituents on the thermotropic behaviour of 2,5-bis[4-(n-perfluoroheptyloctyloxy)benzoyloxy] toluene

Abstract

Lateral n -alkanoyl substituents were introduced at the benzylic position of 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] toluene by free radical bromination followed by esterification with the corresponding potassium n -alkanoates. All of the transition temperatures of the resulting 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] benzyl n -alkanoates decrease relative to those of 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] toluene and with increasing length of the n -alkanoyl substituent. The SmC-SmA transition decreases the most, thereby stabilizing the SmA mesophase and destabilizing the SmC mesophase. In contrast to the well established concept that lateral substituents disrupt smectic layering, none of the 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] benzyl n -alkanoates exhibit a nematic mesophase.