Experimental, QM, And MD Studies On Reversed Micelles And Energetic Systems

In the dissertation, the whole work can be divided into three aspects:The first aspect focuses on the experimental researches on the synthesis and purification of SDSS as well as on the extractions of protein using four reversed micellar systems. Four amphipathic substances—Sodium Dioleyl Sulfosuccinate (SDSS), sodium di(2-ethyl hexyl) sulfosuccinate (AOT), trioctylmethyl ammonium chloride (TOMAC) and cetyltrimethyl ammonium bromide (CTAB) are mainly considered.SDSS has been known to be is an important anion surfactant with extremely good wettability. Synthesizing and purifying it, however, are difficult owing to its special molecular structure. Based on the previous experiments, we improve its synthesis, especially purification methods. The yield is greatly enhanced by prolonging the sulfonation reaction time and replenishing NaHSO3 during the reaction and purifying the product through extraction instead of recrystallization.AOT,TOMAC and CTAB are three kinds of common ionic surfactants. They and self-prepared SDSS have been employed to constitute four different types of reversed micellar systems which are used in the forward and back extractions of cytochrome C (Cyt-C, a water soluble protein) in this dissertation. Various affecting factors including pH value and ionic strength in aqueous phase, phase volume ratio, surfactant concentration, cosurfactant, temperature and time are investigated. Results show that the addition of a small quantity of di (2-ethylhexyl) phosphate (D2EHPA) to SDSS /isooctane reverse micelle is necessary to enhance extraction efficiency of Cyt-C. Similarly, n-octyl alcohol and chloroform to TOMAC/isooctane and CTAB/n-octyl alcohol reverse micelles, respectively. Processes of the back extraction than the forward extraction are harder to work out, and extraction efficiency of the former is lower than that of the latter. The extractions are mainly governed by electrostatic interaction between the protein and the micellar inside walls. What's not clear, however, is that there probably exist other non-electrostatic forces during the back extraction by AOT reversed micelle, such as hydrophobic interaction, etc.In conclusion, SDSS reversed micelle performs an excellent forward extraction effects,100% extraction of Cyt-C from the organic phase with aqueous phase pH 2.0～9.2, cKCl0.5～1。8 mol/L. The extraction efficiencies of both forward and back extractions of Cyt-C are higher employing AOT reversed micelle without the addition of any additive. Therefore, the two types of reversed micelles should be paid more attentions.The second aspect concentrates on the molecular structures and properties of SDSS, AOT, TOMAC and CTAB ions as well as the interactions between the surfactants ions and H2O molecule by the density functional theory (DFT) methods at B3LYP/6-31G* level. Energies from four isomers of SDSS anion display that trans-isomer is more stable than cis-isomer. Polar head—SO3- in trans-isomer is a transmutative tetrahedron. Three S-O bonds are same in length. Two Hydrophobic chains occupy a larger space and contain c=c double bonds not turning freely so that the anion appears some structural characteristic, "head small body big" and the chains "stiff". AOT ion has structural similarities with SDSS ion, yet it is smaller and chains more flexible than those of SDSS ion. Polar head group of TOMAC or CTAB cation is a tetrahedron with nitrogen atom at its center.Actual application of surfactants usually accompanies with water. The interactions between the four surfactants above and H2O molecule have been respectively taken into account in this work. The researches could also help to understand solvent effects and adsorptions on gas-liquid interface of surfactants.It is found that SDSS and AOT ions have similar hydrations, the same case with TOMAC and CTAB ions. Two medium intensity hydrogen bonds are formed by two oxygen atoms of—SO3- with two hydrogen atoms of H2O in monohydrate of SDSS or AOT anion. Water molecule locates at one side of—SO3-. A six-member ring forming by six atoms near the hydrogen bonds tends to make the hydrate more stable. The angle between the chains increases after hydrating, which causes the body of SDSS or AOT anion to become wider. Greater hydration energies (SDSS ion-95.8361 kJ-mol-1 and AOT ion-76.1438 kJ-mol-1) are obtained, which indicates that sulfonate surfactants are good hydrophilic.There are three weak hydrogen bonds in the hydrate of TOMAC or CTAB cation formed by an oxygen atom of H2O and three hydrogen atoms around—NR3+, A cagelike structure consisting of three hexatomic rings composed by eight atoms near the hydrogen bonds enables the monohydrate to be steadier. That the angles between long alkyl chains of TOMAC cation become larger after hydrating brings about a more bulky volume of TOMAC ion. Hydration energies (TOMAC ion-41.7478 kJ·mol-1 and CTAB ion-50. 1499kJ·mol-1) are smaller than those of SDSS and AOT ions, demonstrating that hydrophilicity of quaternary ammonium salt cationic surfactants is not as strong as that of sulfonate anionic surfactants.At present, it is still not vary clear what extraction mechanism of reversed micelles is and some phenomena during the extractions were incomprehensible. Based on the structures characteristics of SDSS anion, some experimental facts are explained such as that the significant extraction can not happen if cosurfactant D2EHPA is not present when SDSS reversed micelles is used. The volumes of SDSS, AOT and TOMAC ions become more expanded after hydration, yet for CTAB ion, such case does not occur. The above foretells that aggregation numbers of reversed micelles for the former three ions are bigger, the latter ion smaller. The conjecture has been verified by the related experiments in this present dissertation.The third aspect centers on structures and properties of 14 energetic composites systems. Molecular dynamics (MD) simulations have been performed on these systems via Universal force field and NVT ensemble. By calculating binding energy and radial distribution function, interactions among the components and the essence of these actions are elucidated. Analysis method of the static mechanics is applied to summarize and compare the varying laws of rigidity, plasticity and ductility of major composites.The binding energies and mechanical properties of 10 energetic systems with two components including PEG/AP,PEG/Al,HMX/MAPO,HMX/PAN,AP/MAPO,AP/PAN,AlH3/HMX,AlH3/CL-20,AlH3/DNOAF和Al/DNOAF are provided. It is found that the binding energies of 3 composites containing AP are all greater, which suggests that AP is compatible easily with other components. The dominant interaction forces of the components in different systems exhibit distinction, Such as, hydrogen bonds in PEG/AP and van der Waals forces in PEG/Al. Greater binding energies occur in the composite containing AlH3, especially in the molecule of its coexisting component having hydrogen atom. Furthermore, for such systems, Young Modulus,Bulk Modulus,Shear Modulus,K/G and (C12-C44) all take on bigger values. This expresses they have stronger rigidity, better plasticity and ductility. The mechanical properties of AIH3/DNOAF are evidently higher than those of Al/DNOAF, foreshowing that replacing Al by AlH3 is probably an option deserving consideration.The Molecular dynamics (MD) simulations are first carried out to study energetic complex systems with four components. Binding energies and mechanical properties of 4 systems involving GAP/NG/BTTN/DNOAF,GAP/NG/BTTN/AIH3,PEG/NG/ BTTN/DNOAF and PEG/NG/BTTN/AIH3 are calculated. Results show that better stability and compatibility can be found from the systems containing AIH3, especially when polyalcohols, such as PEG, coexist. Electrostatic forces are main in such composites as containing AIH3. Young Modulus,Bulk Modulus,Shear Modulus,K/G and (C12-C44) of (PEG/NG/BTTN)/AlH3 are all larger than those of the other 3 systems, which hints that the composite has strong rigidity, good plasticity and ductility. The reason probably involves a special coordinate interaction between PEG and AIH3—having electron-deficient bridge bonds in AIH3 crystal and lone electron pairs in PEG molecule. It is worth to pay close attentions to the formulation containing both AIH3 and PEG.In a word, the three aspects above are integrated into two primary parts in the dissertation:the first part is devoted to researches on the improved methods of synthesis, especially purification for SDSS; on Cyt-C extraction using four different types of reversed micelle systems, which are composed of such surfactants as SDSS, AOT, TOMAC and CTAB; on the geometry and electronic structures of the four surfactants and their hydrates by quantum chemical computational method. Namely, theoretical and experimental researches complement and promote mutually. Some phenomena during extracting using reversed micelles are first explained or predicted by the results from the density functional theory (DFT) methods. The reversed micelles systems of SDSS and AOT perform well and ought to be given more focuses. In the second part, the structures and properties of 14 energetic composites systems are studied through Molecular dynamics (MD) simulations method. The results provide valuable information for the practical formulation designs of energetic composite materials. We recommend especially the formulation the coexistence of AlH3 and PEG. These works are pioneering and innovative, and successfully complete the basic applied research tasks assigned by the Natural Science Foundations of Educational Commission of Jiangsu Province and National Defense "973" project.