Studies On The Lyotropic Liquid Crystallines Formed By Lipids And Imidazolium-Type Ionic Liquids

The self-assembled structures of amphiphile molecules in solvents,such as micelle, vesicle,and lyotropic liquid crystalline phase(LLC)etc.,have attracted more and more attention.As the abundant of structures,LLC is studied widely and applied in several fields,such as synthesis,extraction,catalysis,pharmaceutics,and so on.In order to expand the application of LLC as the drug delivery system and the templates of nanomaterials,the physicochemical properties of two kinds of LLCs formed by lipid and imidazolium-type ionic liquids are studied in the present dissertation.Beside of the component effects on the physicochemical properties of the two kinds of LLCs are studied,the lipid-based LLCs are attempted to be used as drug delivery systems.In the second chapter,the effects of copolymer(F-127)and model drug(procaine hydrochloride,PC)on the structure and theological properties of the cubic LLC formed in monoolein(MO)/water systems are studied by means of Small Angle X-ray Scattering,rheology and FT-IR.It is found that the addition of F-127 could lead to the structure transition from C_D-type to C_P-type cubic phase.The structure transition from C_G-type to C_D-type could also be investigated in the MO/water cubic phase in the present of procaine hydrochloride.The phase transition could consequently induce the change of the theological properties of the cubic phases.The effect of procaine hydrochloride on molecular conformation of MO in the cubic phase is further studied by FT-IR.The results reveal that the arrangement of the hydrophobic carbon chain of MO is strongly affected by procaine hydrochloride.The spectrums of MO/PC/water mixtures are narrower than that of MO/water mixtures,which means that the order of the arrangement of MO hydrophobic carbon chain is increased.The addition of PC is favorable to the kink conformation of CH₂ group.Moreover,with the addition of PC.the H-bond C=O in the polar head group of MO is enhanced.It results from the H-bond between C=O and the N⁺-H in the polar head group of PC.From the change of the FT-IR spectrums,it could be concluded that PC could anticipate forming the lipid bilayer together with MO in the cubic phase.Meanwhile,the discontinuous change of the conformation of MO molecules is corresponding to the structure transition of cubic LLC which is confirmed by SAXS.It is well known that the aqueous dispersion of cubic LLC(cubosome)formed from monoglyceride can be used for the development of drug delivery systems.The cubosome formed based on monoglycerides are obtained by precursor method in the third chapter.The internal structures,morphologies and sizes of the dispersed particles are studied by means of SAXS,electronic microscopy and Dynamic Light Scattering (DLS).It is found that the sizes of the cubosomes are dependent on the carbon chains of the monoglycerides.As the phase transition induced by F-127 in the cubic LLCs.a discontinuous change of the cubosome sizes also could be investigated.In additional, the model drug,caffeine,could induce the phase transition from cubosome to vesicle, because it could destroy the H-bond between head polar group of MO and water molecules.The elementary studies on cubic LLC used as drug delivery systems are involved in the fourth chapter.Firstly,the effects of model drugs,procaine hydrochloride(PC)and ciprofloxacin hydrochloride(CF)on the micellization of two double tailed surfactants. sodium bis(2-ethyl-1-hexyl)sulfosuccinate(AOT)and didodecyldimethylammonium bromide(DDAB),in the aqueous solution are studied in order to reveal the interaction between drug molecules and amphiphiles on molecular level.It is found that the electrostatic attraction between PC and AOT could lead to the reduction of the cmc and equilibrium surface tension of AOT in aqueous solution.The PC-AOT mixed micelle could be formed when the concentration of PC increased to 0.5mmol/L.On the contrary. the electrostatic repulsion between PC and DDAB leads to the incompact package of DDAB molecules in micelle,and the surface tension of aqueous DDAB solutions are slightly increased.The different electrostatic actions between CF and two surfactants cause that the effect on surface properties and the standard thermodynamic functions of micelle formation are different.The electrostatic attraction between CF and AOT could lead to the reduction of cmc of AOT and surface tension in AOT/CF solution,but the increase of the cmc and surface tension in DDAB solution.From the UV results,it reveals that CF is localized in the palisade layer of AOT micelle but the water/micelle interface of DDAB micelle.Secondly,the controlled release of PC from MO/water cubic phases could be achieved because t_1/2is more than 20h,and the release efficiency could attain up to 80%in different systems.The release profiles of PC could be divided into two stages.The release in the two stages both follow the Higuchi quadratic root law. Finally,the effects of copolymers on the drug release behavior from cubosome formed from MO/water systems are also studied.It is found that the release efficiency of Chloramphenicol is dependent on the structure of cubosome,and cubosome is a burst drug release system for lipophilic drugs.In the fifth chapter,the structures of the LLCs formed in 1-alkyl-3-methylimidazolium bromide(C_Nmim-Br,N=12,14,16)/p-Xylene/water mixtures are characterized by Small Angle X-ray Scattering(SAXS),Polarized Optical Microscopy (POM)and ²H-NMR technologies.There are two phases in all of the three systems with different carbon number of the hydrophobic group of C_Nmim-Br,hexagonal and lamellar LLCs,respectively.The structural parameters of the two LLCs are found to be dependent on the carbon number of the hydrophobic group of C_Nmim-Br and the components content.For hexagonal phase,at higher surfactant content,the surfactant molecules aggregate more densely in the cylinder unit of the hexagonal phase;while the cylinder units aggregate more densely in the hexagonal phase.For lamellar phase,the increase of the water content leads to the water channel swell,and the surfactant bilayer is compressed.Meanwhile,the rheological properties of the LLCs are related to the phase structures.In the hexagonal phase,the sample with higher surfactant content has a higher zero-rate viscosity,zero-rate stress and dynamic modulus,which is due to the more dense aggregation of surfactant molecules in the membranes.The viscosity of lamellar phase is dependent on the component contents.Samples with higher content of surfactant or lower water content have the higher viscosity and dynamic modulus. Besides of hexagonal and lamellar phases,there is a bicontinuous cubic phase in the C₁₂mim-Br system,which is investigated by SAXS,POM and ²H-NMR experiments. Moreover,the structural parameters and rheological properties of the C_Nmim-Br-based LLCs are compared with that of the traditional cationic surfactant cetyltrimethylammonium bromide(CTAB)system.It is found that the effects of components content on the LLCs formed from the two kinds of amphiphile molecules are similar.However,the structural parameters and rheological properties of the two systems are different because of the different molecular structure.The studies of the physicochemical properties of LLC formed based on ionic liquid are helpful to the further application of LLC in the nanomaterials preparation.