| The surface tension was measured by the Wilhelmy plate method. The experimental data wereanalyzed by Clint theory and Rubingh theory. The interaction between molecules when themicelle formatted in different systems was studied. On this basis, the phase behavior oflecithin/IPM/H2O, lecithin/Brij97/IPM/H2O and lecithin/AEO20/IPM/H2O systems were studiedby phase diagrams and polarizing optical microscopy. The steady shear measurement, frequencyoscillation and Maxwell model fitting for the liquid crystals studied were carried out to reveal therheological properties and the microstructure of the liquid crystal samples. Some interestingresults were obtained. The application in curcumin invitro release controlled by the liquidcrystals was further studied by the dialysis experiment. All these results will enrich the surfactantresearches both theoretically and practically. In details, the thesis includes four chapters asfollowing:1. The research of aggregates formed by the natural amphiphilicmoleculesOn the basis of the research in many articles related fields at home and abroad, wesummarized the research of aggregates formed by the natural amphiphilic molecules, andfocused on the aggregates formed by lecithin. Including the research of microemulsion, vesicle,organic gel and lyotropic liquid crystal formed by lecithin as the main surfactant. According tothe literature works, the research of microemulsion, vesicle, organic gel and lyotropic liquidcrystal formed by lecithin have become more widely. However, the research of aggregatesformed by lecithin and other non-toxic biocompatible amphiphilic molecules are less. So thephase behavior and rheological properties of the lecithin/AEO20system and lecithin/Brij97system were carried out at the second and third part of this paper respectively. And then theinvitro release of curcumin encapsulated by liquid crystal was studied at the fourth part.2. Phase behavior and rheological properties of lecithin/AEO20systemIn this chapter, the surface tension of lecithin/AEO20system was measured by a Wilhelmytype surface tension-meter. It is found that the pC20values of mixed system are larger than the pC20value of the pure component. By analyzing the molecular interaction parameters （βm） andthe molecule exchange energy （εm） used Clint’s and Rubingh’s treatments, the βmvalues arebetween-9.20and-12.1and all the εmvalues are negative. These reflect that AEO20and lecithinmolecules have a synergistic effect. The rough phase diagrams of lecithin/IPM/H2O andlecithin/AEO20/IPM/H2O systems were determined at37°C by visual observation in normallight and a cross polarizer for anisotropy. The steady rheological results show that all samplesshow shear-thinning behavior. The values of ηγ=0.1and σ0decreased obviously after addingAEO20to lecithin aqueous solutions. Indicated by dynamic rheological results, all samplesexcept sample A2S5show typical gel-like spectra. Moreover the G’ and G″are reduced whenadding AEO20to lecithin aqueous solutions. The Maxwell model fitting for the liquid crystalsstudied were also carried out. Some interesting results were obtained.3. Phase behavior and rheological properties of lecithin/Brij97systemIn this chapter, by measuring the surface tension of lecithin/Brij97, Brij97is able to improvethe efficiency of lecithin reducing surface tension. The molecular interactions were discussed byClint theory. It is found that Brij97and lecithin molecular have an exclusion effect. The phasebehavior and rheological properties of the concentrated lecithin aqueous solutions wereinvestigated at37°C. When adding Isopropyl myristate （IPM） to lecithin solutions, besides ananisotropic liquid crystal （LC） phase, an isotropic liquid （L2） region and an isotropic viscous （I）phase are found. By continuously adding Brij97, the LC region shifts towards higher watercontent and the L2region is extended to the area of lower IPM concentration, meanwhile the Iphase disappears. By analyzing the shear viscosity (ηγ=0.1) and yield stress （σ0）, adding IPM tolecithin solutions increases the values of ηγ=0.1and σ0, and after further adding Brij97, the ηγ=0.1and σ0decrease dramatically. Notably, different from the lecithin/DDAB/water system studied byYoussry and Montalvo, in lecithin/Brij97/IPM/H2O system, at the relatively higher watercontent area of the LC phase, the water content has little effect on the critical stress. It is alsofound that the change of dynamic storage modulus （G’） is similar with that of ηγ=0.1and σ0parameters when adding IPM and Brij97. Maxwell model fitting results show that in the LCphase, the relaxation of the water molecule is prolonged by adding IPM and Brij97to lecithinsolutions. 4. The invitro release research of curcumin encapsulated by liquidcrystal studiedThe invitro release of curcumin encapsulated by the liquid crystal formed by lecithin as themain surfactant was investigated at37℃. Indicated by the dialysis experiment data, the curcumincould be extended released in all the liquid crystal samples. The invitro release results showedthat with increasing the water content, the cumulative release （CR） increase. However, withincrease in the IPM content, the CR changed irregularly. By further investigating the effects ofBrij97and AEO20on the CR, with increasing the Brij97and AEO20content, an increase in CRis observed. |
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