Studies on the synthesis and properties of ferroelectric side chain liquid crystalline polyoxetanes

Two series of novel ferroelectric liquid crystalline (FLC) monomers were derived from 3-(hydroxymethyl)-3-methyloxetane, used as the backbone unit, and 2(S)-[2-(S)-methylbutoxy]propionic acid, as a chiral moiety. The corresponding poly oxetanes were prepared by ring-opening polymerization using BF3 . OEt2 as an initiator. In addition to the structure identification, their liquid crystal phase behavior and electrical properties are also studied. Before their connection to the chiral molecular moiety, two series of carboxylic acids, 4-{6-[(3-methyloxetan-3-yl)methoxy]alkoxy}benzoic acids and 4,4'-[6-(3-methyloxetan-3-yl)alkoxy]biphenylcarboxylic acids, show the phase sequence K-Sc-I and K-Sc-N-I, respectively. After connection, the phase behavior of the corresponding chiral monomers is changed from K-Sc-I to K-Sc*-N*-I as well as from K-Sc-N-I to K-Sc*-Sa-I. Only the phase sequence K-Sc*-Sa-I is observed in both series of polyoxetanes. All of the synthesized monomers exhibited enantiotropic chiral smectic C(Sc*) phase. The monomers, with the biphenyl unit linked directly with a chiral center, possessed higher spontaneous polarization (P-s) values. Polyoxetanes possess a wide temperature range for the liquid crystal phase, about 120 degrees C, and the Sc* phase range can be up to 95 degrees C. However, the position of the biphenyl unit will not affect the spontaneous polarization of the synthesized side chain FLC polyoxetanes. (C) 1997 John Wiley & Sons, Inc.