Thermotropic perfluoroalkyl azobenzoates. Studies of low molar mass compounds and side chain polymer derivatives

A series of 4'-[(carbonyloxy-1,1,2,2-Tetrahydrofluorodecyl)]-4-(omega-bromo -alkenyloxy) azobenzenes, 4'-[(carbonyloxy-1,1,2,2-Tetrahydrofluorodecyl)]- 4-(alk-1-enyloxy) azobenzenes have been synthesised. Also, a polyacrylate h as been formed by phase transfer catalysed reaction between one of the w-br omo-alkenyloxy compounds and sodium polyacrylate as well as two polysiloxan es formed by hydrosilylation of the alkenyloxy compounds and a polyhydrosil ane. All of the low molar mass compounds show the SA phase on heating and a n increase in perfluoroalkyl chain length results in an increase in clearin g temperature whilst an increase in the hydrocarbon chain length shows a de crease in clearing temperature. Upon grafting these low molar mass units to a polymer backbone, the resulting materials also show smectic mesophases d espite having quite low clearing entropies (Delta S/R similar to 0.2 - 0.6) . The precursor polymers are of low molar mass (Mw 1200-1800 g mol(-1)) and this may be the reason why the polymers do not show glass transition tempe ratures.