The Design, Synthesis And Phase Structure Of Columnar Ionic Liquid Crystal Polymers (ILCPs)

Ionic Liquid Crystal Polymers (ILCPs) are a special type of ionicmacromolecular architecture with liquid crystalline property. Combined with liquidcrystalline ordering and ion transport, ILCPs have excellent mechanical property,rheological processability, piezoelectric performance, and optical variableperformance. Herein, we have incorporated the imidazolium cation and differentcounter-anions into the side-chain of polymer with the polyethylene and terephthalicacid ester as the main chain based on “Jacketing” effect to construct two series ofnovel columnar ILCPs. And utilizing the anion-exchange reaction to adjust the kindsof counter-anions, it can be implemented that the structure regulation of the columnarILCPs. It is useful to help us understand the formation of supra-molecule structures inILCPs and which provides a new theory and approach to construct the novelhigh-performance functional polymer materials and liquid crystal composite materials.The mainly research works are as follows:1. A type of ionic liquid crystal (ILC) monomer contained alkyl flexibleside-chain2,5-bis{[6-(1-butyl-3′-imidazolium) hexyl] oxy carbonyl} styrene bis(bromide)(denoted BImHCS-Br) was designed and successfully synthesized. Andthen the other ILC monomers BImHCS-X (Xˉ=BF4ˉ, PF6ˉand TFSIˉ) with differentcounter-anions arrived by the anion-exchange reaction. The chemical structures of theILC monomers were characterized and confirmed by nuclear magnetic resonancespectroscopy (NMR) and fourier transform infrared spectroscopy (FT-IR). And thephase transition and liquid crystalline (LC) properties were inspected by differentialscanning calorimetry (DSC) and polarized light microscopy (PLM), the experimentalresults manifested that all of the monomers with different counter-anions were liquidat room temperature and they did not exhibit LC properties.2. The corresponding columnar ILCPs contained alkyl flexible side-chain, poly(2,5-bis{[6-(1-butyl-3′-imidazolium) hexyl] oxy carbonyl}styrene salts)[denoted aspoly(BImHCS-X)(Xˉ=Brˉ, BF4ˉ, PF6ˉand TFSIˉ)] were successfully synthesized viaradical polymerization based on “Jacketing”effect. The chemical structures andcharacter of the polymers with limidazolium cation and different counter-anions wereconfirmed by1H NMR, FT-IR and gel permeation chromatography (GPC). As well as,the thermal performances were investigated by thermogravimetric analysis (TGA), and the results indicated the kinds of ILCPs had good thermal stabilities. DSC andPLM experiments showed the liquid crystalline behaviours of these PILCs can beobserved except for the sample with the couter-anion TFSIˉ, and the properties can bemaintained to the thermal decomposition.1D Wide-angle X-ray diffraction (1DWAXD) was utilized to investigate the self-assembly and phase structures of thesepolymers, and the results exhibited there was only isotropic phase inpoly(BImHCS-TFSI) because of the large volume counter-anion, but for the otherthree ILCPs, they can form the hexagonal columnar (Colh) ordered structure due tothe strong intramolecular interplay between the counter-anion and imidazoliumcation.3. A series of novel ILC monomers with rigid biphenyl mesogen side-chain,2,5-bis{[6-(4-butoxy-4′-imidazolium biphenyl) hexyl] oxy carbonyl} styrene salts[denoted as (BImBHCS-X)(Xˉ=Brˉ, BF4ˉ, PF6ˉand TFSIˉ)]were successfullysynthesized via multi-step synthesis and anion-exchange reaction method. And theILC monomers were characterized and confirmed by1H NMR, FT-IR and elementalanalysis.4. The corresponding columnar ILCPs with rigid biphenyl mesogen side-chain,poly(2,5-bis{[6-(4-butoxy-4′-imidazolium biphenyl) hexyl] oxy carbonyl} styrenesalts)[denoted as poly(BImBHCS-X)(Xˉ=Brˉ, BF4ˉ, PF6ˉand TFSIˉ)] weresuccessfully synthesized via radical polymerization based on “Jacketing”effect. Thestructures and character of these polymers were affirmed by1H NMR, FT-IR and GPC.TGA experimental results showed that the kinds of ILCPs had excellent thermalstability. DSC and PLM experiments indicated that those ILCPs contained BrˉandBF4ˉhad stable liquid crystalline properties until thermal decomposition, despite thesample with PF6ˉhad the liquid crystalline property as well, but it would disappearafter the temperature exceeded182oC during the heating process, and it would turninto the isotropic state, as for the polymer contained TFSIˉ, it was in the absence ofliquid crystalline behaviour during the process of heating and cooling.1D and2DWAXD experiments indicated the poly(BImBHCS-X) possessing relative smallervolume formed SmA ordered structure during heating and cooling, but forpoly(BImBHCS-TFSI), the large volume of anion TFSIˉdestroyed the packing of LCordered structure, resulting in the formation of amorphous structure. On the otherhand, due to the ionic interaction, the kinds of polymers can exhibit rather interestingphotophysical properties which were consistent with their chemical structures.