溶剂驱动的两亲分子自组织及新型胶体晶体制备

The solvent-effect is a main force driving amphiphiles into self-assembly. In this project, we are designing and synthesizing some surfactants with super-long alkyl chain(s). In the first, we shall dissolve the surfactant in a good solvent and then drop another poor solvent into the solution very slowly, in which the both solvents can well mix but the surfactant is insoluble in the second solvent-alone. By this way, the solution environment gradually becomes less affinity with the surfactant and thus drives these active molecules self-assembling into mono-dispersed and fixed structural aggregates with spherical, ellipsoidal or short-rod shape. It will be studied in detail that the relation of the amphiphilic structure of the surfactant molecule to the solvent-effect driving them self-assembling as well as to the aggregate morphologies. Upon the self-assembly driven by the solvent-effect, a new method for preparing organic noanoparticles is expected to create. Using the mono-dispersed and fixed structural aggregates as the units, new types of colloidal-crystals are expected to fabricate, which includes both two-dimensional single component and binary mixed colloidal-crystal array. The morphologies, structure and optical properties of the colloidal-crystals will be investigated systematically. All these are expected to greatly expand the domain of colloidal-crystals and to enrich and develop new techniques preparing nano-materials. Upon the aggregates formed by the self-assembly of surfactants, the probe molecules with chromophore can be solubilized and thus the optical properties are possible to further improve and even optimize due to the interference and manipulation of light, which will construct the basis to develop new types of sensors and optical materials.

溶剂效应是驱动两亲分子自组织的主要作用力。本项目拟设计合成具有超长烷烃链的极端两亲结构表面活性剂，让其先溶解在一种良溶剂中，再缓慢添加可与第一种溶剂混溶但对表面活性剂不亲和的不良溶剂来改变亲和环境，以此驱动表面活性剂自组织成单分散且结构固化的球形、椭球形、短棒形等聚集体。研究两亲分子极端结构与溶剂驱动效应的关系以及与聚集体形貌的关联，由此可望创造一种制备纳米尺度有机微粒的新方法。将此结构固化的单分散聚集体作为新单元，构筑二维单组分胶体晶体以及不同尺寸、不同形状组合的二元胶体晶体，研究胶体晶体的形貌、结构及光学特性，这有望大大拓展胶体晶体的研究领域，丰富和发展纳米材料制备新技术。利用聚集体单元可加溶生色分子的特性进一步改造胶体晶体的光学性质，结合原生胶体晶体光学特性，探索作为新型传感器或新型光学材料的应用。

第一次将溶剂置换法运用于表面活性剂领域，由此既能制备超长链表面活性剂的均相溶液，又能充分发挥基础驱动力效应推动其自组织。由于表面活性剂分子亲油和亲水基化学本质的悬殊差别，适合的溶剂置换体系有限，我们选择了乙醇/水体系进行考察，证实了水的加入可以引发乙醇中的超长链表面活性剂自组织。这种胶束化过程主要为焓驱动，随着亲和溶剂（水）增加，驱动机理逐渐转变为熵驱动。由于乙醇溶胀了胶束内核，暴露了其中的烷烃尾链，这导致了胶束二次聚集以便降低体系能量。通过灵活运用溶剂置换方法，结合加盐或其它添加剂等措施可以避免二次聚集，获得分散的胶束。例如在C22TABr胶束溶液中加入C18TABr以填补乙醇溶胀造成的分子间隙，同时加水至85 wt%并加NaBr以压缩分子排列，由此获得了分散的球状C22TABr/C18TABr胶束。又如向C18TABr胶束溶液中加入萘磺酸钠（SNphs），加水至90 wt%获得了良好单分散的棒状胶束。将相对大量的苯乙烯增溶进胶束内核并原位聚合，同时借助在富水环境下超长链的不良动力学效应，成功地固结了上述球状C22TABr/C18TABr胶束和棒状C18TABr胶束。