Linear and hyperbranched liquid crystalline polysiloxanes

A series of liquid crystalline (LC) polymers having biphenyl (–C6H4C6H4R; R=H, OC11H23, OC(O)CH(Cl)CH2CH2COOCH2CH3) 4-methoxyphenyl benzoate (–C6H4C(O)OC6H4OCH3) and cholesteryl type mesogenic moieties were synthesized. They were made from respective –Si(CH3)2H terminated mesogens and vinyl functionalized linear and star shape branched polysiloxanes of comb-like and dendritic topologies and were analyzed using WAXS and SAXS techniques. Contrary to the well defined typical dendrimers, in which mesogenic groups are present in an outer sphere, the dendritic systems described here contain such groups also inside the dendritic core. It was found that star shape and dendritic LC structures exhibited various calamitic mesophases (SmA, N* and SmC*) depending on the type of mesogenic groups. On the contrary, the comb-like structures give rise to formation of hexagonal phase, even though they contain typical rod-like mesogenic moieties. For the series of 4-methoxyphenyl benzoate substituted polymers the thorough studies of the relationship between their liquid crystalline properties and topology of siloxane skeleton was determined. Mechanical properties of the LC materials were also studied.