Studies On The Properties Of Ionic Liquid-Based Microemulsions And The Preparation Of Functional Polymers

Ionic liquids, due to their excellent properties, such as high ionic conductivity, immeasurably low vapor pressure, good thermal and electrochemical stability, benign to environment, are suitable for incorporation into polymers. The obtained ionic liquid-polymers afford the completely compatible combination of ionic liquid and polymer. Evidently, the promising application foreground of them in lithium batteries and capacitors and is brought forth. Recently, protic ionic liquids(PILs)which can act as proton-carriers are attracting progressively increasing interest due to their potential uses as electrolytes in fuel cells. the development of proton exchange membranes (PEMs) with little or no dependence on humidity at temperatures above 100°C is still remains an important challenge to realization of practical Fuel cells.However, the successful preparation of ILs-based polymer electrolytes is critically denpendent on the compatibility between the ILs and polymeric matric. In this paper, we report the preparation and polymerization of microemulsions that contain IL polar cores dispersed in a polymerizable oil, and the IL nanostructures formed in these microemulsion could be preserved in the resultant polymeric matric throught the polymerization of oil-continuous phase. The research demonstrated that we solved the microscopic phase separation since in the case of a membrane, the IL and polymer bicontinuous networks can be obtained. Furthermore, a series of ionic liquid-polymer electrolytes based on them were prepared. The main study contents were as follows:Firstly, three kinds of surfactants-like ionic liquid: 1-dodecyl-3-methyl imidazoium bromide(a-Br), 1-(2-acryloyloxyundecyl)-3-methyl imidazolium bromide(c-Br), 1-(2- methyl acryloyloxyundecyl)-3-methyl imidazolium bromide(b-Br), were synthesized. And these two kinds of surfactants (b-Br) and (c-Br) are polymerizable.Secondly,ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate Bmim[BF₄] was synthesized. And a series of protic ionic liquids: 1-methylimidazolium trifuorometh -anesulfateHMim[TfO], 1,2-dimethylimidazolium trifuoromethanesulfate DMim[TfO], 1-buthylimidazolium trifuoromethanesulfate HBim[TfO], 1,2-dimethylimidazolium tetrafluoroborate DMim[BF₄], 1-methylimidzolium tetrafluoroborate HMim[BF₄], 1-methylimidazolium nitrate HMim[NO3], were easily synthesized through the combination of a Br?nsted acid and Br?nsted base.Threely, these pseudo-ternary phase diagrams of ionic liquid/surfactant/monomer were determined by titration measurement, such as Bmim[BF₄]/a-Br/St system, Bmim[BF₄]/b-Br/St system, Bmim[BF₄]/c-Br/St system, Bmim[BF₄]/b-Br/VAC system, Bmim[BF₄]/b-Br/MMA system, Bmim[BF₄]/b-Br/DMAA system, HMim[TfO]/b-Br/ (AN/St) system, DMim[TfO]/b-Br/(AN/St) system, HEim[TfO]/b-Br/(AN/St) system. Phase behaviors of these systems were studied.Then, the microemulsion consisting of ionic liquid/surfactant/monomer were initiated with photoinitiator (benzoin ethyl ether) under UV lamp, to form ILs-based polymer electrolytes and PILs-based polymer electrolytes.Divinylbenzene was added as a cross-linker. This systems also were initiated with 2,2-azobis(isobutyronitrile) (AIBN) at 60℃, No apparent visible phase separation could be observed during and after the polymerization process. The following conclusion were obtained:1) The TGA data show that the thermal degradation temperature of the composite membranes is about 250℃.2) The AFM results of the fracture cross section of the composite membranes indicate that ionic liquids are dispersed well. When it is a ILs/O microemulsion system, the ILs droplets with the diameter of 20nm are dispersed in polymeric matric; When it is a bicontinuous(B.C.) systems, IIs and polymer bicontinuous netwoks appear like long and winding channel of 10-30nm size domain.3) The conductivity of the composite membranes was measured with an alternating current impedance spectroscopy. For a membrane containing 45wt% of HEim[TfO] or DMim[TfO], the conductivity is about 10-2 S/cm at 160℃.4) Dynamic mechanical thermal analysis (DMA) show that ILs/polymeric matric clearly display one maxima on the tanδvs T curves. The ILs don't undergo phase-Separation upon curing the composite membranes. So, the network of the composite membranes is asymmetric. The mechanical strength of resultant polymer electrolytes can be easily tuned by varying of monomer and the amount of cross-linker added.