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以具有氢键形成结构基础的甘氨酸和范德华作用堆积倾向的胆固醇作为结构单元,以直链脂肪二酸为连接臂,通过DCC缩合,设计、合成并表征了5种双胆固醇衍生物.根据连接臂所包含亚甲基个数的不同,将这些化合物依次表示为1,2,3,4,5.系统考察了这些化合物在25种常见溶剂中的胶凝行为,结果表明,连接臂长度对化合物胶凝能力影响显著.其中,化合物1可以胶凝11种所测试溶剂,且最低胶凝浓度均不超过1.0wt%,化合物2可以胶凝其中的17种溶剂,化合物3可以胶凝11种,连接臂更长的化合物4和5则只能胶凝2种或者4种有机溶剂.SEM观察表明,连接臂长度对胶凝剂分子的微观聚集形貌也有显著影响.此外,聚集体形貌还与溶剂本性有关.值得注意的是,化合物2,3,4,5对DMSO的胶凝行为和在其中的聚集行为均表现出有趣的奇偶效应,即2和4可使DMSO胶凝,而3和5则不能使该溶剂胶凝,此外,2和4在其DMSO凝胶中形成容易折断的条片状聚集体,而3和5则以球状聚集体从DMSO中析出.FTIR分析表明,相对于自由态,聚集态时2,3,4,5的酰胺键N?H、C=O的伸缩振动和N?H的弯曲振动峰所对应波数呈现出明显的奇偶效应(即波数随连接臂碳原子个数增加呈交替变化).XRD分析表明,在上述4种聚集体中,只有2,3,4呈现出显著的衍射信号,且具有典型的层状排列特征,即d1:d2:d3=1:1/2:1/3.相反,化合物5的聚集体没有明显的衍射信号,聚集体中分子排列无序.此外,2、3、4的衍射强度也以强弱强的规律变化,考虑到5几乎没有衍射信号,可以认为从DMSO中所分离出来的2,3,4,5的X射线衍射信号也表现出奇偶效应.对2/苯凝胶体系的FTIR与变温1HNMR研究表明,胶凝剂分子间氢键作用是凝胶形成的主要驱动力之一.综合FTIR,1HNMR和XRD分析结果,提出了胶凝剂分子在有关溶剂中的可能聚集方式,即通过氢键作用相邻分子的连接臂聚集靠近,通过范德华作用相邻分子的胆固醇片段聚集靠近,进而形成有序排列的片层结构.
Five kinds of bi-cholesterol derivatives were designed, synthesized and characterized by condensation of DCC with linear aliphatic diacid as linker and glycine with a hydrogen bond formation structure and cholesterol with a vanten accumulation tendency as the structural unit. Including the number of different methylene groups, these compounds were expressed as 1, 2, 3, 4, 5. The system investigated the gelling behavior of these compounds in 25 common solvents, the results show that the length of the linker arm on the compound Among them, compound 1 can gel 11 kinds of tested solvents with the lowest gelling concentration not more than 1.0wt%, compound 2 can gelatinize 17 kinds of solvents, compound 3 can gelatinize 11 kinds, Compound 4 and 5, which have longer linker lengths, can gel only 2 or 4 organic solvents.SEM observations show that the length of the linker arm also has a significant effect on the microscopic aggregation morphology of the gellant molecules.In addition, It is noteworthy that compounds 2, 3, 4, 5 exhibit interesting odd-even effects on both the gelling behavior of DMSO and the aggregation behavior therein, ie, 2 and 4 gel the DMSO and 3 And 5 do not allow the solvent to gel, in addition, 2 and 4 are in place Its DMSO gel formed easily disintegrating lamellar aggregates, while 3 and 5 precipitated as spherical aggregates from DMSO.FTIR analysis showed that the free-form, when aggregated state 2,3,4,5 amide The wave numbers corresponding to the flexural vibrations of N? H, C = O and the flexural vibration of N? H show obvious odd-even effects (that is, the wavenumber alternates with the increase of the number of carbon atoms in the linker) .XRD analysis shows that in the above Of the four aggregates, only 2, 3 and 4 exhibited significant diffraction signals with typical lamellar arrangement, ie, d1: d2: d3 = 1: 1/2: 1/3. In contrast, In addition, the diffraction intensity of 2,3,4 also changes strongly and strongly, considering that there is almost no diffraction signal of 5, it can be considered that it is separated from DMSO The X-ray diffraction signals of 2, 3, 4, and 5 also show odd and even effects. The FTIR and 1HNMR studies of 2 / benzene gel system show that hydrogen bonding between the gelling agents is the main driving force for gel formation As one of the forces, based on the results of FTIR, 1HNMR and XRD analysis, we proposed the possible aggregation of gelator molecules in the relevant solvents, ie, the adjacent molecules Of the connecting arms gather close, the neighboring molecules through Van der Waals effect the aggregation of cholesterol fragments close to form an ordered arrangement of the lamellar structure.