Hydrogen bonding and liquid crystallinity: The connection

A family of novel liquid crystalline side-chain polysiloxanes has been built through self-assembly via intermolecular hydrogen bonding between hydrogen bond donor and acceptor moieties. Poly(methylsiloxane)s and poly(methyl-co-dimethylsiloxane)s with side-chains containing 4-alkoxybenzoic acid pendant groups attached through aliphatic spacers were synthesized for use as H-bond donor polymers. Liquid crystallinity was induced in complexes of non-mesogenic donor polysiloxanes and stilbazoles. The structure of the stilbazole in the H-bonded moieties were varied to give mesogenic structures possessing a wide latitude of transition temperatures.; The role of the complex geometry in influencing mesogenicity was addressed through blends of isomeric alkoxybenzoic acid substituted polysiloxanes and stilbazoles. As expected mesophase stabilization resulted only from blends having a overall linear structure. Spontaneous polarization was induced in self-assemblies having an optically active stilbazole as an acceptor. The versatility of the two component approach was tested through mesophase induction in H-bonded structures having stilbazole-N-oxide as an acceptor function.; The phase diagrams were established using synchrotron X-ray data, differential scanning calorimetry and optical microscopy. X-ray diffraction studies on unoriented samples point to smectic C or smectic A phases for these materials.