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

Abstract

Poly(4-vinylpyridine)s (P4VPs) fully and partially quaternized with dialkyloxyterphenyl groups were synthesized and characterized. These new polymers developed both liquid-crystalline (LC) properties and a light emission (luminescence) in the blue region. The mesomorphic behavior of the polymers was initially characterized by differential scanning calorimetry and polarizing optical microscopy and was further corroborated by X-ray diffraction analyses. The X-ray diffraction patterns showed in the low-angles region several equidistant diffraction peaks (d 001 , d 002 , d 003 , . . .) and in the wide-angles region a broad peak typical of nonordered mesophases. From d 001 and the length of the monomers, we deduced that the molecular arrangement in the mesophase corresponded to a double-layered stacking of molecules with mesogens tilted with respect to the smectic plane and the backbones sandwiched between. In this arrangement, the different parts of mesogens are segregated from one another in layered domains. The longer smectic periods observed for copolymers indicated that the nonsubstituted pyridine cycles were sandwiched between two smectic layers. The emission spectra of these polymers were characterized by a broad signal centered at 365 nm. The combination of LC properties with luminescence in the polymers is interesting for the preparation of thin films with aligned emitters, particularly for linearly polarized light emission.

Ionic Liquid Crystals: Versatile Materials

“…Bazuin suggested that the ordered LC mesophase that is shown by some low molecular weight ion pairs with small anions can disappear in favor of a disordered smectic phase after ionic complexation with an anionic polymer backbone . It is remarkable that tilted smectic phases, such as the SmC phase, are seldom observed for truly ionic mesogens, ,− ,,− while these are common phases for neutral LCs. , Some disk-like ionic mesogens, obtained via ISA and carrying “switchable” side chains, were shown to exhibit lamellar phases instead of expected columnar phases. , …”

“…The occurrence of such strong π–π stacking in addition to the electrostatic interactions resulted in complete segregation of the different molecular components into ionic, aliphatic, and aromatic sublayers. Polymerized 4-vinylpyridinium analogues of 250- m / n are also LC …”

Liquid‐crystalline and photo‐induced properties of P4VP quaternized with bromo derivative of dialkyloxy‐phenyleneazobenzene groups

“…The quaternization of 4VP with Azo‐Br was also carried out at 80 °C (72 h) in a large excess of 4VP (5 mL of the monomer 4VP:0.25 g of Azo‐Br). The obtained quaternized monomer is unstable and polymerizes once formed . Such a spontaneous polymerization occurs only between quaternized monomers (despite the presence of 4VP) affording a 100% quaternized polymer (here named P4VP‐100).…”

“…A small amount of hydroquinone was added to this reaction to inhibit the formation of the nonquaternized P4VP through the thermal‐induced free‐radical polymerization of the 4VP monomer. The partially quaternized polymers (copolymers) were obtained from a P4VP prepared according a procedure described in a previous report . This P4VP was reacted with 20 and 50% mol of Azo‐Br in dry DMF at 90 °C during 72 h. The obtained P4VP copolymers were named P4VP‐20 and P4VP‐50, respectively.…”