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 (d001, d002, d 003, ⋯) and in the wide-angles region a broad peak typical of nonordered mesophases. From d001 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. © 2010 Wiley Periodicals, Inc.