The research objects of this paper were to design bolaamphiphilic gelators utilizing a sugar family as a source of solvophilic groups and an azobenzene segment as a solvophobic group and to monitor the aggregation mode utilizing the spectroscopic properties of the azobenzene chromophore. The results indicated that the bolaamphiphiles act, although only for specific DMSOâwater mixtures, as gelators and form a unique supramolecular helical structure in the gel phase. The UV-Vis and CD spectra showed that the azobenzene segments adopt H-type face-to-face orientation and the dipole moments are arranged in the right-handed (R)-helicity. Since the fibrils as observed by electron microscope possess the right-handed helical structure, one may consider that the microscopic azobenzeneâazobenzene orientation is reflected by the macroscopic supramolecular structure. When boronic acid-appended poly(L-lysine) was added, the gel phase was changed into the sol phase in the macroscopic level and the fibrous aggregate was changed into the vesicular aggregate in the microscopic level. These changes, which are usually induced by a temperature change, are due to the specific boronic acidâsugar interaction occurring at the constant temperature. Interestingly, when D-fructose which shows high affinity with the boronic acid group was added, the sol phase and the vesicular aggregate were changed back to the gel phase and the fibrous aggregate, respectively. This means that the phase and morphological changes in the sugar-integrated bolaamphiphiles can be controlled reversibly.
本文的研究对象是设计以
糖类为溶亲基团来源、以
偶氮苯片段为溶疏基团的双亲凝胶剂,并利用
偶氮苯染料的光谱性质监测其聚集模式。研究结果表明,虽然双亲分子仅在特定的
DMSO-
水混合物中作为凝胶剂发挥作用,但它们在凝胶相中形成了独特的超分子螺旋结构。UV-Vis和圆二色光谱(CD)显示,
偶氮苯片段呈现H型面对面取向,其偶极矩排列为右手性(R)螺旋。由于电子显微镜观察到的纤维具有右手螺旋结构,可以认为微观的
偶氮苯-
偶氮苯取向反映了宏观的超分子结构。当添加了具有羧基的聚(
L-赖氨酸)时,凝胶相在宏观层面上转变为溶液相,细纤维聚集体在微观层面上转变为囊泡聚集体。这些变化通常是由温度变化引起的,但在恒定温度下由特定的
羧酸-糖相互作用引起。值得注意的是,当添加与
羧酸基团具有高亲和力的
D-果糖时,溶液相和囊泡聚集体分别重新转变为凝胶相和细纤维聚集体。这意味着,糖整合的双亲分子的相和形态变化可以被可逆地控制。