Manipulating ordered structure of ionic liquid crystalline polymers through tuning the alkyl spacer length

Abstract

The fabrication of ordered structure is very important for the applications of ionic liquid crystalline polymers (ILCPs) or polymerized (ionic liquid crystal) (PILC). In this paper, we reported a facile approach to manipulate the ordered structure of ILCPs through adjusting the length of alkyl spacer. We designed and synthesized a series of ILCPs contained imidazolium, poly(2,5-bis{[m-(4-butoxy-4′-imidazolium phenyl) m-alkyl] oxy carbonyl} styrene bis (fluoroborate) salts) (denoted as P4-m−BF4, m represents the number of carbon in the alkyl spacers and m = 2, 4, 6, 10) via radical polymerization. Combined differential scanning calorimetry (DSC), polarized light microscopy (PLM), X-ray scattering, and two-dimensional wide-angle X-ray diffraction (2D WAXD), we found that the ordered structure of this ILCPs can transfer from smectic A phase (SmA) to hexagonal columnar (ΦH) phase with the increase of spacer. Furthermore, these results were confirmed by reconstructed relative electron density map using fast fourier transform algorithm (FFT). The result revealed that the increase of alkyl spacer would affect the interaction between ions and side chain, and induce the packing of the side chains. It was evident that the alkyl spacer played an important role in the constructing of ordered structure and offered a new method to fabricate different ordered structure of ILCPs.