Supramolecular hydrogen-bonded liquid–crystalline polymer complexes. Design of side-chain polymers and a host–guest system by noncovalent interaction
✍ Scribed by Takashi Kato; Norifumi Hirota; Akira Fujishima; Jean M. J. Fréchet
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 448 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
Supramolecular liquid-crystalline polymeric complexes based on a backbone that contains vinyl pyridine units and azobenzene or biphenyl derivatives that posses alkyl chains terminated by carboxylic acid have been obtained by the formation of intermolecular hydrogen bonds between the carboxylic acid and the pyridyl moieties. The polymeric complexes behave as side-chain liquid-crystalline polymers and exhibit smectic phases. A new type of H-bonded host-guest liquid-crystalline system is also reported. The liquid-crystalline host copolymers contain both mesogenic acrylate and 4-vinylpyridine units. The guest molecule is an azobenzene that has a carboxylic acid moiety at one of its extremities. The H-bonded polymeric host-guest complexes exhibit nematic phases. Sequential UV and visible light irradiation of the polymeric complex causes reversible photochemically induced phase transitions. The isothermal nematic-isotropic and isotropic-nematic transitions result from the trans-& and cis-trans photoisomerization of the guest azobenzene in the hostguest system.