Synergistic Effects Of Surfactant Mixtures And Polymer/Surfactant In Oil/Water And Foam Systems

Mixed surfactants and surfactant/polymer have been widely used in a variety of industrial and commercial applications area because it had remarkably characteristic properties and superior performance, such as reducing the total amount of surfactant. Most of the current researches focus on mixed micellar aggregates, whereas a few have specifically considered the role of the surfactant and polymer at the oil/water interface. In the paper, we used MD and DPD simulations, combining a variety of experiments, such as surface tension, interfacial tension, interfacial rheology, etc., to investigate and summarize the synergism mechanisms of mixed surfactants in oil/water interface and air/water interface at different levels and specific interaction in surfactant/polymer mixed system.This paper was divided into three parts. Firstly, it presents the interface behavior of single-component surfactant system by molecule simulations, including DAOS, DSB, 6501, GMS and PEG-100. On the one hand, surfactant with one head and one tail had been used as a basic model in DPD to investigate the factors affecting the interface tension by verifying the interaction parameters between molecular fragments systematically. On the other hand, the influence of temperature on surfactants behavior has been investigated by determining x parameter. Finally, surfactant resisting temperature and salinity is designed according to the above results.Secondly, simulations and experiments were adapted to investigation the molecule behavior of mixed surfactants (DAOS and 6501, DSB and 6501, GMS and PEG-100). The results included the following three aspects:the cavities at the interface layer formed by ionic or zwitterionic surfactants were filled with nonionic surfactant cluster, which made interfacial efficiency and interfacial density high to obtain synergism; mixed surfactants arranged in a staggered manner with double rows at foam, which showed water molecules were locked and difficult to lose; adding salt would play a very important role on producing synergism for anionic surfactants and zwitterionic surfactants. A high-stable foam system have low interface tension has been designed according to the above results.Thirdly, interfacial rheology, apparent viscosity and simulation techniques were adapted to investigation the properties of two kinds of pH-sensitive polymers PAA and TR-1. Viscosity of aqueous solution and aggregates behavior in bulk phase had been studied at different pH. The impact of groups of molecules on viscosity had been revealed. It was found that the hydrophobically modified polymer TR-1 adsorbed at oil-water interface, while TR-1 would be replaced by PEG-100 if the concentration of PEG-100 is high enough. The hydrophobic effect is the driving force for the form of TR-1/PEG-100 complex.On the basis of experiments and simulations, the properties of mixed surfactants and surfactant/polymers complex were evaluated. The key mechanisms of the technology segments were found out, and the relation between molecule structure, behavior and property were put forward. There was a great significance for the above research to direct the application of surfactant and polymer in many practical processes, especially in enhance oil recovery for high salt and temperature reservoir. The innovations in the thesis are as follows:1. For the first time DPD had been utilized to investigate the factors affecting the interface tension using surfactant with one head and one tail as a basic model and verifying the interaction parameters between molecular fragments systematically.2. For the first time, the MM method had been used to evaluate the effect of temperature on behavior and character of surfactants and a molecular design approach for temperature-toleranted surfactants was built up.3. Co-adsorption behavior of mixed surfactants at oil/water and air/water interfaces was investigated by MD and DPD in different level, and the synergistic effects and mechanism have been found out.4. The effect of inorganic ions on the molecular behavior of surfactants at interfaces had been investigated by MD simulation, it was found that saltinity play an important role on the symergism effect of mixed surfactants.5. Aggregation behavior of pH-sensitive polymers and mixtures of surfactant PEG-100 and TR-1 had been characterized by DPD, and interaction mechanisms between surfactant and had been investigated combining the experimental methods and molecular simulation techniques.