Synthesis of stereoregular liquid-crystalline alicyclic polyethers by cationic ring-opening polymerization

We have synthesized main-chain type liquid-crystalline alicyclic polyethers , i.e,, 2-substituted poly(4-oxycyclohexane)s, by cationic ring-opening pol ymerization of racemic 7-oxa-bicyclo[2.2, 1]heptanes (OBH's) as monomer. Op tically pure (+)-exo-2-phenyl-7-oxabicyclo[2.2.1]heptane ((+)-POBH) and (-) -POBH were separated by optical resolution on a silica gel column coated wi th cellulose phenylcarbamate. The optically pure monomers and monomer mixtu res with various proportions were polymerized by Lewis acid catalysts in hi gh vacuum, The NMR data suggested that stereoregular polymers were obtained from optically pure monomers. The poly((+) POBH) and poly((-)POBH) had a h igh specific rotation of +536 degrees, suggesting that the polymers take a helix conformation. The stereoregularity of polymers from optically pure mo nomers was higher than that of polymers from mixture monomers. The opticall y pure polymers exhibited liquid crystallinity. These polymers showed a nem atic phase in the temperature range from T-g (152 similar to 195 degrees C) to approximately 310 degrees C.