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

Abstract

SUMMARY: 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.

Synthesis and liquid‐crystalline properties of poly(4‐vinylpyridinium) bromides N‐substituted with dialkyloxyterphenyl groups

“…In a previous study, we observed 4‐vinylpyridine (4VP) N ‐substituted with an alkyloxybiphenyl mesogen polymerizes spontaneously leading to a fully quaternized poly(4‐vinylpyridine) (P4VP) 6. This specific polymerization method was used to prepare P4VP N ‐substituted with different mesogens; however, there has been no report on the use of π‐conjugated cores longer than a biphenyl group 7, 8. P4VP N ‐substituted with biphenyl cores through a flexible spacer normally develops single‐layer smectic phases with upright molecules (or mesogens) laterally arranged head to tail, as was deduced for pyridine N ‐substituted with similar mesogens 9, 10.…”

Main‐chain ionene polymers based on trans‐1,2‐bis(4‐pyridyl)ethylene exhibiting both thermotropic liquid‐crystalline and light‐emitting properties

“…On the one hand, both cationic and anionic polymers, also known as ionene polymers, have received considerable interest because they are the appropriate polymers for the construction of functional multilayer assemblies by a sequential layer‐by‐layer deposition technique through electrostatic interactions 1–10. On the other hand, the liquid crystallinities, that is, both the thermotropic and lyotropic liquid‐crystalline (LC) properties, of ionene polymers have also received considerable attention in the field of LC polymers 11–26. Cheng et al27, 28 described the thermotropic properties of a series of ionene polymers prepared from the quaternization reaction of trans ‐1,2‐bis(4‐pyridyl)ethylene with X(CH 2 ) n X (where n is 4–10, 12, or 16 and X is mesylate or tosylate).…”

Synthesis and Characterization of Poly(pyridinium salt)s with Organic Counterions Exhibiting Both Thermotropic Liquid-Crystalline and Light-Emitting Properties

“…Thus, their emission spectra can be tuned at will by adding a charged species to the nitrogen site via by manipulating their electronic structures. [1][2][3][4][5][6][7][8][9][10][11] Besides their electroluminescent properties, [1][2][3][4][5][6][7][8][9][10][11] conducting 16 and liquid-crystalline (LC) [17][18][19] properties of suitably designed polymer structures make them attractive materials in many technological applications. However, the two other main-chain poly-(pyridinium salt)s are of considerable interest.…”