Synthesis and characterization of new chiral side chain liquid crystalline polyoxetanes

Abstract

Two series of the side chain liquid crystalline polyoxetanes were synthesized via cationic ring-opening polymerization of oxetane monomers bearing pendant mesogenic units including two chiral carbons. The first two polymers have only one pendant group in the repeating unit, whereas the second polymers have two mesogenic groups per repeating unit. The oxetane monomer bearing one mesogenic unit produced high molecular weight polymers, whereas the ones bearing two mesogenic units at the same carbon in the ring produced only oligomeric products. Thermal and liquid crystalline properties of the polymers were investigated by optical polarizing microscopy, differential scanning calorimetry (DSC), and small- and wide-angle X-ray diffractometry. All of the polymers, with the exception of only one polymer, formed liquid crystalline phases such as S-A, S-C*, and S-I* phases in melts. The molecular arrangement in the smectic phases was interpreted as an intercalated bilayer structure. An attempt to study the ferroelectric properties of the polymers was made, but the results obtained were not satisfactory.