Thermotropic liquid crystalline behaviour of pyridinium and poly(4-vinylpyridinium) salts quaternized with ω-alkyl phenylbenzoate derivatives

✍ Scribed by Patrick Masson; Philippe Gramain; Daniel Guillon

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 58 KB
• Volume: 200
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/(sici)1521-3935(19990301)200:3<616::aid-macp616>3.0.co;2-4

✦ Synopsis

The synthesis, thermal properties and organisation of side-chain liquid-crystalline (SCLC) polysalts and of their analogous low molecular weight (LMW) pyridinium salts are described. They contain three distinct parts: a phenyl benzoate aromatic core, a flexible aliphatic chain (6 or 12 methylene units) and a pyridinium group associated with bromine counterions. The polysalts are obtained upon spontaneous anionic polymerisation of 4-vinylpyridine in the presence of 4-methoxyphenyl 49-(x-bromoalkoxy)benzoate. Fully quaternised polymers of high molecular weights are obtained. Their thermotropic polymorphism was studied by means of differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. Despite the presence of the spacer and of a mesogenic group known for its nematogenic character, only smectic A mesophases were observed for the LMW pyridinium salt with the longer spacer (C 12 ) and for the polysalts with the two spacer lengths (C 6 , C 12 ). These compounds were shown to form in a large range of temperature a single layered structure. An organisation model is proposed in which the pyridinium cations and the aromatic cores are perpendicular to the layer, while the spacers adopt a disorganised conformation.