Thermotropic Perfluoroalkyl Azobenzoates. Studies of Low Molar Mass Compounds and Side Chain Polymer Derivatives

Abstract

A series of 4′-[(carbonyloxy-1,1,2,2-Tetrahydrofluorodecyl)]-4-(ω-bromo-alkenyloxy) azobenzenes. 4′-[(carbonyloxy-l,1,2,2-Tetrahydrofluorodecyl)]-4-(alk-l-enyloxy) azobenzenes have been synthesised. Also, a polyacrylate has been formed by phase transfer catalysed reaction between one of the ω-bromo-alkenyloxy compounds and sodium polyacrylate as well as two polysiloxanes formed by hydrosilylation of the alkenyloxy compounds and a polyhydrosilane. All of the low molar mass compounds show the SA phase on heating and an increase in perfluoroalkyl chain length results in an increase in clearing temperature whilst an increase in the hydrocarbon chain length shows a decrease in clearing temperature. Upon grafting these low molar mass units to a polymer backbone, the resulting materials also show smectic mesophases despite having quite low clearing entropies (ΔS/R ∼ 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 temperatures.