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The lirst cahe of reentrant phenomenon in disc-llke mesogens was observed in hexaalkmoyloxytruxenes (Cn HATX) In t h s senes of ten compounds ( n = 6 to 15) a few of them, the long cham ones, displayed a reentrant columnar phase On the other hand, a reentrant ND nematic senes was prepared. truxene p-alkoxybenzoates (Cn HBTX) with n = 6 to 14 Phase transitions between sohd, mesomorpfuc and isotropic phases were studied by hot-stage microscopy and differential scanhlung calonmctry Binary phase diagram studies, optical textural observations and X ray measurements showed a rich polymorphsm in these two senes' a nematic disc like phase ( N D ) , a hexagonal ordered columnar phase ( Dho), a hexagonal disordered columnar phase ( Dhd), a rectangular disordered columnar phase [ Drd(p2,/,)] and a strongly tilted rectangular columnar phase [ D r d (~~/ m ) lThe following mesophase sequences in these two senes were found +Presented at the Ninth International Liquid Crystal Conference,

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