NOVEL FLUORINE-CONTAINING FERROELECTRIC SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANES SHOWING BISTABLE FAST SWITCHING

A series of new ferroelectric liquid-crystalline polymers consisting of a polysiloxane main chain with a side chain of 4-([1-(trifluoromethyl)alkoxy(n)]carbonyl)phenyl 4'-alkoxy(m)biphenyl-4-carboxylate (5) were synthesized by the direct polycondensation of the corresponding liquid crystalline dichlorosilane monomers with water. The mesogenic dichlorosilanes were prepared by the hydrosilylation of the mesogenic compounds possessing terminal olefine with dichloromethylsilane in the presence of hexachloroplatinic acid. The liquid crystalline polymers were characterized by differential scanning calorimetry (DSC), optical polarizing microscopy (OPM), and electrooptical studies as well. All the polymers displayed an enantioropic smectic A phase (S(A)) and a broad chiral smectic C (S(c)*) phase, where the S(c)* phase persisted even below 20-degrees-C. The polymer molecular weights were in the range of 4.5 x 10(3) to 11.0 x 10(3). These materials showed bistable fast switching in the oriented samples (2.7-mum cells) having the response time of a few hundred microseconds, the shortest response time reported so far for liquid crystalline polymers, driven by a rectangular wave voltage of +/- 50 V. Spontaneous polarization of the polymers was found to be in the range of 32-122 nC/cm2 at T(c) -30-degrees-C (T(c) = S(A)-S(C)* transition temperature).