【作者】 陈美玲；

【导师】 王正武；

【作者基本信息】 江南大学 ， 应用化学， 2010， 博士

【摘要】 大分子体系的理论计算一直是具有挑战性的研究领域,尤其是表面活性剂大分子体系的理论研究具有重要意义。运用量子化学方法研究表面活性剂的定量结构-性质关系,可以帮助人们进一步了解表面活性剂的电子结构与表面活性剂性质之间的结构关系,从而有目地的修饰表面活性剂的结构、设计并合成新型的表面活性剂。运用量子化学方法研究表面活性剂与溶剂分子间的相互作用和表面活性剂的自组装等,有利于分析表面活性剂在界面吸附时的结构变化以及与溶剂分子间相互作用的实质。论文用量子化学方法研究表面活性剂与溶剂分子间的相互作用,不仅能带动量子化学方法在表面活性剂领域中的应用,而且能从理论上为更好地解释表面活性剂在气液界面上的吸附及自组装特性提供理论参考。浊点(Cloud Point,CP)是非离子表面活性剂的一个重要参数,它在非离子表面活性剂的实际应用中起着很重要的作用。因此,建立表面活性剂的分子结构与其浊点的定量-结构关系(quantitative structure-property relationship,QSPR),根据QSPR来设计、筛选或预测新化合物的浊点,将会对非离子表面活性剂的应用起重要的指导作用。本研究用反映表面活性剂分子空间结构信息的拓扑学参数:价连接性指数0J和价键连通性指数χv,以及0级Kier & Hall指数KH0作为描述符,建立起了非离子表面活性剂浊点与分子结构的定量结构-性质关系(QSPR)模型,模型复相关系数R2=0.962,明显好于目前所报到的QSPR模型。亲水亲油平衡(Hydrophile-Lipophile Balance, HLB)值是用来定量表示表面活性剂双亲性质相对大小的经验指标。本研究用反映分子微观电子结构和空间形态方面的量子化学参数作为主要描述符建立了两种阴离子表面活性剂亲水亲油平衡(HLB)值的定量结构-性质关系模型,两种模型复相关系数R2均大于0.99。以常见的烷基硫酸盐为例,探讨了量子化学方法在表面活性剂领域的应用。采用量子化学方法中的密度泛函理论,对CH3OSO3? (H2O)n(n=1-8)存在的所有几何构型进行了全优化。用结合能二阶差分的方法分析不同水合物的稳定性。结果表明CH3OSO3?至少与六个水分子相互作用形成稳定结构的水合物。对CH3(CH2)mOSO3? (H2O)6(m=9)水合物的水合层面积进行了计算。首先对该水合物用B3LYP/6-31+G(d)方法优化,然后计算水合层-SO4? (H2O)6的体积,然后再根据体积计算得到水合层半径为4.27 ?,其横截面积为57.2 ?2,计算结果与文献中的实验结果非常接近。C6F14、C8F18及CF3CH2OH (三氟乙醇,TFE)等氟碳化合物在低压蒸汽条件下具有表面活性,被称为挥发性表面活性剂。蒸汽氟碳表面活性剂的发现对于从原子水平了解这一现象的物理学提出了理论挑战。目前关于挥发性表面活性剂的实验研究及理论研究很少。本研究运用量子化学方法研究挥发性表面活性剂的分子结构、与溶剂分子间相互作用及自组装。通过对三氟乙醇的理论研究,发现:(1)三氟乙醇不论是cis构型还是trans构型,水作为质子受体形成的水合物比水作为质子供体形成的水合物稳定。三氟乙醇单体的焓、自由能及恒容热容与温度均成很好的线性关系;(2)三氟乙醇多聚体以氢键的形式相互作用。生成多聚体的过程是放热过程。在25℃时,0-6.66kPa压力下三氟乙醇自组装的可能性很小,主要以单体形式存在,这一结论与实验结果一致。而且在293.15-363.15K温度范围及对应的饱和蒸汽压下△G>0,多聚体不能自发形成,即三氟乙醇不能自组装。为了研究CF3CH2OH的表面活性,从理论上研究了CF3CH2OH与水的相互作用。结果表明在常温常压下,CF3CH2OH至少和三个水分子能自发形成水合物。此水合物在25℃,3-90kpa范围内进行热力学分析发现:在25℃,P<40kPa时,?G>0,说明水合物不能自发形成。当P>40kPa,?G<0,水合物可以自发形成。说明CF3CH2OH在40kpa低压条件下,可以自发吸附在水的表面,降低水的表面张力。TFE和水分子之间的相互作用为放热过程。通过对C6F14和C8F18氟碳化合物的理论研究,结果表明:(1) C6F14和C8F18的焓、自由能、熵及恒容热熔均与温度和压强呈线性关系;从焓变、熵变及自由能分析,C6F14和C8F18在低温低压条件下分子间的相互作用增强。二聚化、三聚化和四聚化是放热过程。(2) C6F14和C8F18的二聚体、三聚体及四聚体均在最低温度和最低饱和蒸气压时△G最小,进一步说明C6F14和C8F18作为挥发性表面活性剂,在低温低蒸汽压条件下多聚体更容易形成;(3) C8F18单体和CH3CH2OH分子之间的相互作用很弱(属于很弱的氢键)。C8F18在CH3CH2OH界面上吸附是吸热过程。更多还原

【Abstract】 Theoretical calculation of macromolecules has been challenging area of research, especially in surfactant system. In this paper, quantitative structure-property relationship (QSPR) for surfactants is investigated. This helps better understanding of the relationship between the electronic structure of surfactant and properties of surfactants, and modifies structure of surfactant as well as designs and synthesizes a new type of surfactant. Then, interactions of surfactant with solvents and adsorption of surfactant at the interface were discussed with quantum chemistry method. It will not only provide theoretical reference for explaining the adsorption of surfactant at the interface, but also enlarge the application of the quantum chemistry method in surfactant area.The cloud point is an important property of nonionic surfactants and plays an important role in their applications. A QSPR for cloud point would allow us to sift and predict the cloud point of new compounds. Using the quantum chemical parameters, topological indexes and physical chemistry parameters as descriptors, a QSPR for the cloud point of nonionic surfactants has been found for nonionic surfactants. The correlation coefficient of multiple determination is as high as 0.962. The obtained model is significantly better than the previous. Two QSPR models for the hydrophile-lipophile balance (HLB) value of anionic surfactants were established by using the quantum chemical parameters for the first time. The correlation coefficient (R2) is larger than 0.993.This paper, taking the most commonly used alkyl sulfate surfactant for example, explored quantum chemical methods in the field of surfactants. The interaction of alkyl sulfate surfactant with water molecules was studied by using DFT. It was revealed for the first time that alkyl sulfate surfactant formed stable hydrate with six water molecules when it was saturation adsorption at the air - water interface. The area of hydration for CH3(CH2)mOSO 3? (H2O)6(m=9) was investigated. The calculated results showed that area of the hydrophilic group is 57.2 ?2, which is similar to the experimental results.The volatile fluorocarbon surfactants( such as CF3CH2OH, C6F14 and C8F18) need not be dissolved in liquid,only cover the liquid surface at low vapor pressure with the result of reducing the surface tension of a liquid. In this work, we aim to study the self-association of volatile surfactant by using quantum chemical method. We have investigated the interactions between volatile surfactant and the interaction of volatile surfactant with solvents. The main results were obtained through theoretical study of CF3CH2OH:(1)For configurations of cis-TFE and trans-TFE, hydrate in which water is as proton acceptor is more stable than the hydrate in which water is as proton donor. For TFE monomer, enthalpy, Gibbs free energy and Constant volume heat capacity have linear relationship with temperature. (2)TFE molecules link to each other through hydrogen bonds. The formation of polymer is an exothermic process. TFE exists mainly in the form of monomer at 25℃with the pressure 0-6.66kPa. This result is consistent with the experiment results. Moreover, the formation of dimers is nonspontaneous. And the TFE is little associated at different vapor pressure data in the ranges 293.15-363.15K. (3)TFE can interact with at least three water molecules at 298.15K and 1 atmosphere. The interaction of TFE with water molecules is an exothermic process. The interaction of TFE with three water molecules at 298.15K in the pressure range 3-90kpa is discussed. The calculated results showed that the values of ?G are positive at 298.15K and P<40kpa, indicting that adsorption of TFE at the air -water interface is nonspontaneous. The values of ?G are negative at 298.15K and P>40kpa, indicting that adsorption of TFE clusters at the air -water interface is spontaneous.The main results were obtained through theoretical study of C6F14 and C8F18. (1) For C6F14 and C8F18 monomer, enthalpy, Gibbs free energy and constant volume CV have linear elationship with temperature. From the analysis of the enthalpy change, entropy change and free Energy change, Intermolecular interactions for C6F14 and C8F18 were enhanced at lower temperature and pressure. Polymerization process is an exothermic process. (2)The Dimers, trimers and tetramers for C6F14 and C8F18 have the smallest△G value at the lowest temperature and the lowest saturated vapor pressure. This further reveals that the formation of polymerization is easier at lower temperature and the lower saturated vapor pressure. (3) C8F18 and CH3CH2OH have very weak interactions. Adsorption of C8F18 at the surface of CH3CH2OH is an endothermic process.更多还原