Theoretical Studies Of Surfactant On QSPR, Interfacial Adsorption And Self-Assembly

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.