具有介观溶解现象的体系的热力学行为研究

The addition of the hydrophobic component into hydrotrope aqueous solutions may result in the formation of mesoscale droplet in the solution rather than molecular solution or macro-phase separation, which is called "mesoscale solubilization" and shows wide applications in many fields like drug delivery and industrial cleaning, etc. However, researches on the mesoscale solubilization were limited in detecting the formation or transition of mesoscale structure in solutions containing short-chain alcohols as hydrotropes, and investigations on their thermodynamic properties and the influences of the mesoscale structure on the critical phenomena are rather scarce. This project will take {water+hydrotrope+hydrophobic component} as research systems (where water and hydrotrope may be replaced by proper ionic liquids). The measurements of density and heat capacity, isothermal titration calorimetry and static/dynamic light scattering for these systems will be carried out to obtain the apparent molar volume, the apparent molar heat capacity, the conditions for the formation or transition of mesoscale structure, particularly their thermodynamic characteristics. Moreover, the experimental investigations of the critical phenomena for proper systems will be designed to inspect the influence of mesoscale structure on the critical universality of the critical exponent and the critical amplitude ratio, as well as the critical crossover behavior. This project will not only explore and construct a thermodynamic process for study of systems with mesoscale structure and acquire the corresponding precise thermodynamic data, but also deepen the understandings on these systems thus lay the foundation for the extension of their applications.

疏水物质加入到水+助溶剂二元溶液中，既未在分子尺度混合又未产生宏观相分离而是形成介观尺度液滴的现象被称作介观溶解，它在药物载体，工业清洗等领域有着重要的应用价值。目前对于介观溶解的研究主要通过散射技术鉴定介观结构的存在与转变，且大多局限于以短链醇作为助溶剂的体系,极少报道对介观体系中的热力学行为及介观结构与临界涨落的交互作用的研究。本项目将以{水+助溶剂+疏水物质}为研究体系(其中水及助溶剂还可选用合适的离子液体代替)，通过密度和热容测量，等温滴定量热，静/动态光散射等手段获得这类体系中相应组分的表观热力学性质，介观结构形成及其转变的条件和热力学特征；通过对存在介观结构的溶液的临界现象的研究，考察介观结构对临界指数、指前因子比的普适性以及临界跨接行为的影响。本项目不仅探索和构建具有介观溶解现象体系的热力学研究方法，获得准确的热力学数据，而且可以深化对助溶机理的认识，为拓展其应用提供基础。

本项目以一系列{水+助溶剂+疏水物质}溶液为研究对象，测量了{水+乙醇+1-辛醇}等4个体系的密度，热容等热力学性质；采用光散射，电导率，拉曼光谱，荧光光谱，GC-MS等手段对{2-丁氧基乙醇+水+聚二甲基硅氧烷(PDMS)}等7个体系的微观结构及物性进行了测量；考察了疏水物质在水+胆碱氨基酸离子液体体系中的增溶情况；测量了水+2，6-二甲基哌啶体系在微量环己烷存在时的临界性质。通过对所研究体系的实验结果的分析讨论得：（1）水+助溶剂体系中存在的特定疏水物质是介观结构产生的主要原因，疏水物质应具有较强的疏水性以及较多可与助溶剂相作用的官能团；（2）助溶剂不仅可用于增加疏水物质在水中的溶解度，也可以用于在疏水介质中增溶水，对于离子液体型助溶剂，可通过离子液体寡聚体包裹水分子的形式来实现对水的增溶；（3）介观结构的形成和转变过程伴随着热力学性质的变化，可以通过对体系热力学性质的精确测量实现对介观溶解现象的研究；（4）助溶剂的亲/疏水性以及助溶剂与疏水物质间的相互作用是影响疏水物质在水+助溶剂体系中增溶效果的主要因素；（5）介观结构的存在对二元溶液的液液临界性质影响显著，对临界温度的影响较大，对临界组成的影响相对较小。上述结论对深化人们对于介观溶解现象的产生机制和助溶剂的助溶机理的认识有着重要意义，为介观溶解现象的更广泛的应用提供了重要的理论依据。