【作者】 周乐乐； 毕研慧； 于丽；

【Author】 Lele Zhou;Yanhui Bi;Li Yu;Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education;

【机构】 山东大学胶体与界面化学教育部重点实验室；

【摘要】 利用咪唑类表面活性离子液体（SAIL）—1-十六烷基-3-甲基咪唑溴(C₁₆mimBr)和光敏有机小分子—偶氮苯羧酸钠（AzoCOONa）在水溶液中构筑了光响应粘弹性蠕虫状胶束;设计合成了两种含肉桂酸根的咪唑类表面活性离子液体—1-十二烷基-3-甲基咪唑肉桂酸盐([C₁₂mim][CA])和1-十二烷基-3-甲基对羟基咪唑肉桂酸盐([C₁₂mim][PCA]),研究了其在水溶液中的光响应聚集行为。分别采用流变和低温透射电子显微镜（Cryo-TEM）技术研究了[C₁₆mimBr]:[AzoCOONa]的浓度比为2:1时体系的宏观性质和微观结构。发现紫外光（365 nm）照射之后,起初形成的蠕虫状胶束变长、粘度也提升了一个数量级,原因可能是C₁₆mimBr和AzoCOONa分子间的cation-π作用对胶束生长的促进作用大于AzoCOONa分子光异构化导致亲水/疏水平衡作用、空间位阻以及静电吸引作用的变化对胶束生长的阻碍作用。表面张力和电导率的研究结果表明[C₁₂mim][CA]的表面活性高于[C₁₂mim][PCA]。当增大表面活性离子液体的浓度时,[C₁₂mim][CA]能够形成六角液晶和立方液晶,而[C₁₂mim][PCA]则在较大的浓度范围内仅形成六角液晶相。在光响应过程中,本文研究的体系均未发生聚集体类型的变化。[C₁₆mimBr]/[AzoCOONa]构建的蠕虫状胶束展现了可控的粘弹性行为;而肉桂酸根的光异构化使得[C₁₂mim][CA]和[C₁₂mim][PCA]的表面活性减弱,六角液晶的结构排列得更加紧密。本文构筑的光响应聚集体在药物释放、生物化学和材料制备等领域有着潜在的应用前景。更多还原

【Abstract】 The UV-light-stimulated behavior of viscoelastic wormlike micelles formed by a surface active ionic liquid（SAIL）, 1-hexadecyl-3-methylimidazolium bromide(C₁₆mimBr), and an azobenzene derivative, sodium azobenzene 4-carboxylate（AzoCOONa）, was investigated in aqueous solution. Two imidazolium-based SAILs with cinnamate aromatic counterions, viz. 1-dodecyl-3-methylimidazolium cinnamate([C₁₂mim][CA]) and 1-dodecyl-3-methylimidazolium para-hydroxy-cinnamate([C₁₂mim][PCA]), were newly synthesized, and their photo-responsive behaviors in aqueous solutions were systematically explored. The properties and structures of the aggregates formed at a concentration ratio equal to 2:1([C₁₆mimBr]:[AzoCOONa]), were comprehensively characterized by rheometer and cryogenic transmission electron microscopy（Cryo-TEM）. Upon irradiation by UV light（365 nm）, particularly fascinating is that the length of the initially formed wormlike micelles became longer and their viscosity increased by one order of magnitude. The cation-π interaction between C₁₆mimBr and AzoCOONa molecules prevailing over the hydrophobic interaction and electrostatic interaction caused by photoisomerization of the AzoCOONa molecule is supposed to be responsible for this peculiar phase behavior. Results of surface tension and conductivity measurements show that [C₁₂mim][CA] displays a superior surface activity than [C₁₂mim][PCA] in aqueous solutions. Both hexagonal liquid-crystalline phase（H1） and cubic liquid-crystalline phase（V2） were constructed in the [C₁₂mim][CA] aqueous solutions when increased the concentration of SAIL. In contrast, the [C₁₂mim][PCA]/H2 O system only exhibits a single hexagonal liquid-crystalline phase（H1） in a broad concentration region. It is the first time that, with exposure to UV or visible light, the aggregate type of the photo-responsive system has remained unchanged. The wormlike micelles constructed by [C₁₆mimBr]/[AzoCOONa] system exhibit controllable viscoelastic behavior in the photo-responsive process. Under UV irradiation, trans-cis photoisomerization of the cinnamate aromatic counterions results in inferior surface activity of [C₁₂mim][CA] and [C₁₂mim][PCA]. The photo-responsive ordered aggregates constructed in this work are expected to have potentials in the fields of drug delivery, biochemistry and materials science, etc.更多还原