Formation, Properties And Applications Of Ordered Aggregates In Ionic Liquids, Ethylammionium Nitrate

In this thesis,we studied the formation,properties and potential applications of aggregates by nonionic and anionic surfactants in room-temperature ionic liquids (RT-ILs),ethylammonium nitrate(EAN).Furthermore,carbon nanotubes(CNTs) were stably dispersed in RT-ILs and the inorganic-organic hybrid materials were fabricated.The thesis is separated five parts,which are summarized as following:In the first section,the structure,properties,synthesis and application of ionic liquids are outlined;the aggregation behavior of surfactants in ionic liquids is summarized;and finally,the structure,properties and application of carbon nanotubes are outlined.In the second section,the dispersion of mutil-walled carbon nanotubes (MWCNTs)within hexagonal lyotropic liquid crystals(LLCs)formed by nonionic polyoxyethylene surfactant C₁₆EO₆ in room-temperature ionic liquids(RT-ILs), ethylammonium nitrate(EAN),was studied.The results indicate MWCNTs were dispersed evenly within LLCs.The introduction of MWCNTs does not destroy the structure of hexagonal LLCs.The increase of d spacing combined with the enhancement of phase transition temperature from LLCs to isotropic solution demonstrates the integration of MWCNTs within the cylinders of the hexagonal LLCs. FT-IR and Raman spectra further confirm that the MWCNTs have been incorporated in the LLC phase.The rheological results indicate that MWCNTs-LLC composites are highly viscoelastic and that the apparent viscosity is enhanced due to the introduction of the MWCNTs.In addition,the tribological properties were explored,which could greatly extend the applications of MWCNTs-LLC composites in RT-ILs as lubricating materials.In the third section,the dispersion of carbon nanotubes(CNTs)in ethylammonium nitrate(EAN)by nonionic surfactants(Tween-20,Tween-60 and Tween-80)was studied.The results indicate that Tween surfactants in EAN exhibit good dispersion ability for CNTs.The stably dispersed CNTs in ionic liquid can not coagulate even after centrifugation at high speed.The micelles formed by Tween surfactants in EAN could play an important role for the stably dispersed CNTs,which were determined by surface tension measurements.Raman and UV-vis-NIR absorption spectra confirm that the single-wall carbon nanotubes(SWCNTs)were evenly dispersed in EAN. Transmission electronic microscopy(TEM)images indicate the CNTs are exfoliated to form individual tubes.In the forth section,the aggregation behavior of sodium laurate(SL)in ethylammonium nitrate(EAN)was studied.The results indicate an ionogel was formed in EAN because of a chemical reaction between SL and EAN, CH₃(CH₂)₁₀COONa+CH₃CH₂NH₃NO₃→CH₃CH₂NH₂↑+NaNO₃↓+ CH₃(CH₂)₁₀COOH.Polarized optical microscopy images indicate that the ionogels are birefringent,illuminating the presence of anisotropic structure.Small-angle X-ray scattering(SAXS)measurements reveal that SL and lauric acid(LA)molecules formed by chemical reaction are arranged to form lamellar structures but no SL crystallites were confirmed by the X-ray Diffraction(XRD)measurements.With an increase of SL concentration,the interlayer distance decreases.The intermolecular hydrogen-bond of SL and LA as well as the solvatophobic interaction between EAN and acid-soap formed by SL and LA could play a role in the formation of three-dimensional networks,which result in the formation of the anisotropic ionogels. Rheological measurements indicate that the ionogels are highly viscoelastic and that the gel strength increases with the increase of SL concentration.Moreover,the ionogels have good resistance against mechanical stress.The electrochemical measurements indicate that the gels have higher conductivity,better electrochemical stability,and a wide electrochemical window,therefore illuminating the potential application in the fields of electrochemical devices.In the fifth section,the manganese(â…¡)-substituted polyoxometalate, (Na₆(NH₄)₄[(Mn^â…¡(H₂O)₃)₂(WO₂)₂(BiW₉O₃₃)₂]·37H₂O(POM-Mn)was assembled in hexagonal lyotropic liquid crystals(LLCs)formed by C₁₆EO₆ in EAN,fabricating the POM-LLC inorganic-organic hybrid materials.The results indicate,after the introduction of POM-Mn,the system still remains the hexagonal structure.The increase of d spacing combined with the enhancement of phase transition temperature from anisotropic phase to isotropic solution demonstrates the integration of POM-Mn within the basic unit of the hexagonal LLCs.FT-IR spectra further confirm that the POM-Mn have been incorporated in the LLC phase.The rheological results indicate POM-LLC hybrid materials are highly viscoelastic and that the apparent viscosity is enhanced due to the introduction of the POM-Mn In addition,the magnetic properties were explored,the results indicates the POM-LLC hybrid materials show ferromagnetism,therefore illuminating the potential application in the fields of magnetic materials.