| Imidazolium surfactants are based on imidazolium salts with long hydrophobic alkyl chains which can exhibit novel aggregation behavior that differs from conventional surfactants and form liquid crystals assemblies due to the delocalized electrons on the imidazole ring and the hydrogen bonding between imidazole rings.Imidazolium surfactants are assembled with other functional building blocks through multiple intermolecular interactions（such as electrostatic interactions,π-πinteractions and intermolecular hydrogen bonds,etc.）,and the assemblies can not only improve the properties of materials but also respond to external stimuli through synergistic effect.The controllable self-assembly of new ordered molecular can be realized,which is expected to discover novel soft materials and expand their applications by effectively utilizing the multifunctional designability of imidazolium surfactants and choosing suitable building unit.In this paper,we systematically investigated the molecular design,synthesis and characterization of imidazolium surfactants with liquid crystal properties,as well as the controllable self-assembly between imidazolium surfactants and other functional building units and the properties of the assemblies.The main research contents and conclusions were as follows:First,two ionic liquid type polyoxometalates[C16Mim]2[W6O19]and[C18Mim]2[W6O19]were synthesized by using sodium tungstate,1–hexadecyl–3–methylimidazolium bromide and 1–octadecyl–3–methylimidazolium bromide as the main raw materials.The results showed that[C16Mim]2[W6O19]and[C18Mim]2[W6O19]had good thermal stability and can exist stably before 330℃.The melting point and brightening point of[C16Mim]2[W6O19]and[C18Mim]2[W6O19]were 74.6℃,97.5℃and 83.7℃,116.4℃respectively.The layered structures of[C16Mim]2[W6O19]and[C18Mim]2[W6O19]were further confirmed by variable temperature XRD measurements results.Second,a novel imidazolium surfactant with azobenzene group in side chain（abbreviated as CAzo CM）was designed and synthesized by 4-acetamidopheol,1-bromododecane,1,10-dibromododecane as well as 1-methylimidazole.The surfactant was self-assembly with graphene oxide to form an imidazolium surfactant-graphene oxide hybrid（abbreviated as CAzo CM-GO）.The results showed that graphene oxide was partially reduced by CAzo CM due to strong electron effect of imidazole units and RGO was dispersed more uniformly in CAzo CM.CAzo CM exhibited Sm A phase,with a focal cone texture when cooled.The introduction of GO didn’t destroy the liquid crystal structure of CAzo CM and the liquid crystal properties also retained in CAzo CM-GO.CAzo CM was switched from trans to cis isomer in270 s when was irradiated at 365 nm and from cis to trans isomer in 660 s when was irradiated at 550 nm.CAzo CM-GO had a more sensitive response behavior,the photo-responsive time from trans to cis isomerization became 110 s under ultraviolet while the photo-responsive time from cis to trans isomerization became 195 s under visible light.Third,we designed and prepared an imidazolium surfactant containing an azobenzene group at the end group（abbrev.as Azo CM）with 4-phenylazophenol,1,10-dibromodecane,and 1-methylimidazole as the main raw materials.In the same time,we prepared[N（C4H9）4]2[H2Zn Mo6O18{（OCH2）3CCH2CH3}2]（abbreviated as TBA-Zn Mo6）.Finally,Azo CM and TBA-Zn Mo6 were self-assembled to form a new hybrid（abbrev.as Azo CM-Zn Mo6）.We found the thermal stability of Azo CM-Zn Mo6was improved.Azo CM had liquid crystal phase during the cooling process,and a spherical liquid crystal texture was observed.Azo CM was standard lamellar liquid crystal structure was confirmed by XRD.When irradiated at 365 nm,Azo CM changed from trans to cis isomer in 205 s,and when irradiated at 550 nm,it changed from cis to trans isomer in 595 s.The hybrid Azo CM-Zn Mo6 had a light response time of 295 s for trans-cis isomerization and 185 s for cis-trans isomerization. |
PDF Full Text Request