Hydrogen-Bonded Liquid-Crystalline Polyurethane Complexes with 4-Dodecyloxybenzoic Acid

Gabriela Ambrožič, Majda Žigon*
National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia E-mail: majda.zigon@ki.si

We prepared novel hydrogen-bonded liquid-crystalline polyurethane complexes from 4-dodecyloxybenzoic acid and polyurethane containing pyridyl units in the main chain, based on 2,6-bis(hydroxymethyl)pyridine. The complexes were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. The liquid-crystalline polyurethane complexes were formed at acid/pyridine molar ratios up to 0.4 exhibiting crystal-smectic and smectic-nematic transitions similar to those of the polyurethane complexes with pendant pyridyl units reported on recently. The analogous low-molar mass urethane complex exhibited lower isotropization temperature and a less ordered smectic phase than the polymeric complexes.

Key words: supramolecular polyurethanes, hydrogen bonding, 4-dodecyloxybenzoic acid, liquid-crystalline polymers (LCP)