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含糖胆固醇衍生物的合成及其胶凝行为
【作者】 高迪；
【导师】 房喻；
【作者基本信息】 陕西师范大学 ， 材料学， 2010， 硕士
【摘要】 不同于化学凝胶,物理凝胶的三维网络结构是由胶凝剂分子通过氢键、范德华力、π-π堆积、疏溶剂、静电以及偶极等分子间的弱相互作用维持的。物理凝胶的这种弱相互作用特征决定了其具有良好的热可逆性以及一些奇特的性质,因而在药物缓释、凝胶电池、组织工程支架和温和分离等领域具有潜在的应用价值。形成物理凝胶的胶凝剂可以是聚合物、无机微纳米颗粒,或者小分子量化合物,其中以小分子量化合物备受人们关注。主要是由于：(1)与凝胶对应的溶液态与纯溶剂有着相近的粘度；(2)此类胶凝剂相对容易获得,且易于改性修饰,因此易于放大制备：(3)此类胶凝剂在理论上可以燃烧,为凝胶的现实应用奠定了基础。糖类化合物含有多羟基,分子间存在很强的氢键作用,其衍生物是一类重要的两亲性小分子胶凝剂。由于胆固醇分子片段之间的范德华相互作用使得胆固醇类衍生物易于在溶液中发生簇集,因此,胆固醇类衍生物是一类重要的小分子胶凝剂。基于这些认识,本学位论文立足于实验室对胆固醇类小分子胶凝剂多年研究的基础,将胆固醇和糖类化合物结合,以两亲性小分子胶凝剂的研发为主要内容,主要开展了以下四个方面的工作：第一部分：通过连接臂的改变,设计合成了4种含有直链葡萄糖的胆固醇类小分子胶凝剂(分别以化合物1,2,3,4表示,图1)。利用核磁技术、红外光谱和元素分析等方法对这些化合物的组成和结构进行了表征,均得到了比较满意的结果,为系统地研究这些化合物的胶凝行为奠定了基础。第二部分：系统考察了所合成的四种化合物在常见有机溶剂中的胶凝行为。化合物1-4都既可以胶凝质子性溶剂(戊醇等),也可以胶凝非质子性溶剂(二甲苯等)。化合物2,3,4在二甲苯中的胶凝浓度分别为0.09,0.022,0.016%(w／v),是二甲苯的超级胶凝剂,并且可以在二甲苯中形成罕见的超分子凝胶薄膜(图2)。各化合物胶凝溶剂的种类随连接臂的增长而增加。凝胶的稳定性研究发现,随着连接臂的增长,凝胶的相转变温度逐渐升高。凝胶的流体力学研究发现化合物的力学性能对化合物的连接臂以及化合物在体系中的浓度存在依赖性。扫描电镜研究发现化合物连接臂的改变对凝胶的微观形貌也有显著的影响。第三部分：利用红外光谱、变温变浓度核磁共振等手段探讨了凝胶的形成机理。利用X－射线衍射研究发现,化合物1在戊醇中的干凝胶是呈层状堆积方式,与其在固体粉末中的堆积方式类似。根据以上的探讨,提出了化合物在凝胶中的堆积模型。第四部分：设计合成了4个含乳糖的胆固醇类两亲型小分子胶凝剂,研究了所得化合物在多种有机溶剂中的胶凝行为、胶凝性质以及成胶机理,相关数据见附录。
【Abstract】 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.