Sugar Cholesterol Derivatives And Their Gelation Behavior

Unlike chemical gels, physical gels only involve non-covalent interactions (e.g., hydrogen bonding,π-πstacking, van der Waals interaction, coordination interaction, etc.) between gelator molecules. Generally speaking, these gels are thermo-reversible and display fascinating properties of both fundamental and practical values including drug delivery devices, gel electrolyte based batteries, scaffolds for tissue engineering, and mild separation, etc. Within the physical gels, the gelators could be polymers, inorganic micro-nano-particles, and low-molecular mass compounds, which are called low-molecular-mass-gelators (LMMGs). LMMGs are more attractive than others due to a number of reasons:(1) dissolution of the gels formed by them may result in solution of similar viscosity to pure solvent; (2) these gelators are much easier to be modified and created, and thereby much more gelators and gels can be developed; (3) these gelators are, at least in theory, degradable and combustible, which bring gels more chances in real life applications.Sugar, which contains several free OH groups, has been used to make special amphiphilic gelators. At the same time, cholesterol derivatives have been the subject of attention in the field of low-molecular-mass-gelators due to their outstanding gelation performances. Based upon the knowledge described above and as a continuation of our group studies of cholesterol derivatives as low molecular-mass organic gelators, a series of cholesterol-based and sugar-contained LMMGs were synthesized and studied. This dissertation is mainly composed of the following four parts:In the first part, four novel LMMGs containing both glucose and cholesterol unit, which are denoted as 1,2,3, and 4, respectively, have been synthesized. The structures and compositions of all these compounds are characterized by 1H NMR, FT-IR spectroscopy, and elemental analysis, and satisfied results have been obtained.In the second part, the gelation properties of the four compounds were examined systematically in common organic solvents. Clearly, Compounds 1-4 show similar gelation behaviors, they gel both protic and aprotic solvents, such as pentanol, xylene. The number of solvents gelled by the compounds increases along with increasing the linker length of them.2,3, and 4 in xylene are only 0.090%,0.022%, and 0.016%(w/v), respectively, which are significantly lower than 0.1%(w/v), a well recognized critical value for "super-gelators". Interestingly, Compounds 2,3, or 4 can form supramolecular gel films in xylene. Tgel and rheological studies revealed that the stability and porporties of the gels depend on the length of the spacers of the compounds. SEM studies revealed that the linker length has a great effect upon the aggregation mode of the gelators and the structures of the gel networks.In the third part, we studied the mechanisim of the formation of the gels. FT-IR and 1H NMR spectroscopy studies revealed that intermolecular hydrogen bonding formation plays an important role for the formation of the gels. XRD studies showed that 1 possesses a layered structure in its 1-pentanol gel, a similar structure to that of it in solid state. According to the discussion above, a structural model was proposed to describe the formation of gel network.In the forth part, four novel amphiphilic cholesterol-based lactose-containing LMMGs were designed and prepared. The gelation behaviors, the propreties of gels and the mechanism of gelation formation of compounds were studied, the data were shown in appendix.