Research on self-assembling gemini surfactants and other amphiphiles for potential gene delivery applications in research as well as in clinical practice, and as alternatives to viral gene delivery vectors, is beginning to focus more on structureactivity relationships to address the current low gene delivery efficiencies of amphiphiles. Some underlying structureactivity relations are beginning to emerge. But, as a better understanding of the factors that govern the transfection abilities of amphiphile molecules emerges, development of improved non-viral vectors with clinical potential may also emerge.<p> The research conducted for this thesis was aimed at the design, synthesis and in vitro investigation of gemini surfactants as one of a family of novel amphiphiles being investigated for gene therapeutic applications. The properties of these compounds can be controlled as well as allowed to vary naturally. Gemini surfactant-based gene delivery systems were prepared and characterized for transfer of Luciferase plasmid (pMASIA.Luc) to both COS-7 and PAM 212 cells. Characterization was accomplished using microscopy, dynamic light scattering (DLS) and zeta (ζ) potential analysis. In vitro gene expression and toxicities were evaluated in COS-7 cell and PAM 212 keratinocyte cultures.<p> The level of in vitro transfection in general was found to correlate strongly with the structure of the gemini surfactants. Among the 12-spacer-12 surfactants, incorporation of a pH-sensitive aza (N-CH3) group, which is also steric hindrance-imposing, in the spacer chain yielded increased transfection, particularly for the 12-7N-12 surfactant. In comparison, the incorporation of the more pH-sensitive imino (N-H) group in the 12-7NH-12 surfactant yielded the highest increase in transfection among the 12-spacer-12 surfactants. The deleterious effect of steric hindrance due to the aza group is more evident when comparing the transfection efficiency of 12-5N-12 (1 × aza, higher) vs. 12-8N-12 (2 × aza, lower transfection). Another highlighted structural feature is provided by the fact that both the 12-7NH-12 and 12-7N-12 surfactants had higher transfection efficiencies than 12-5N-12 and 12-8N-12 surfactants; the first pair has trimethylene spacing, which constitutes an optimal separation between nitrogen centres, while the second pair has shorter dimethylene spacings.<p> After expanding the structure of surfactants, transfection efficiencies were found to increase in response to increase in hydrocarbon tail length, but were much lower for surfactants with no amino functional groups, those that lacked the optimal trimethylene spacing, or those having both of these limitations in the gemini surfactant spacer. The 18-7NH-18 surfactant had the highest overall transfection in both COS-7 and PAM 212 cells. Gemini surfactant-based gene delivery systems capable of adopting both polymorphic structural phases and which could undergo pH-induced structural transition demonstrated high transfection efficiencies. Gemini surfactants with both characteristics (e.g., 12-7NH-12-based complexes are both polymorphic and pH-sensitive) had higher transfection than gemini surfactants with only one (e.g., 12-3-12-based complexes are only polymorphic).<p> Overall, the m-7NH-m surfactants, the most efficient surfactants studied, had transfection efficiencies similar to that of the commercial Lipofectamine Plus reagent and imposed no higher toxicity on cells relative to the less efficient surfactants. Thus, the design of the m-7NH-m surfactants to enhance their transfection abilities also ensured that their toxicity to cells were kept minimal. Overall, the design, synthesis and in vitro transfection screening of gemini surfactant candidates has revealed that the m-7NH-m surfactants have the highest transfection efficiencies; they have emerged as suitable candidates for non-viral gene delivery in vivo or at higher levels. Gene delivery investigations for six of the gemini surfactant candidates are being reported for the first time.

We apply a molecular dynamics (MD) simulation technique to complex molecules at interfaces. Partitioning of dendritic surfactants into clay gallery and Ab protein behavior near hydrated lipids are chosen for the purpose. Using a full atomistic model of dendritic surfactants, the confinement force profiles featuring oscillatory fashion at moderate layer separation of 10 to 25 Å were observed. Integration of the confinement forces led to free energy profiles, which, in turn, were used to determine the final morphology of the nanocomposite. From the free energy profiles, smaller and linear surfactants (G1 and G2L) are expected to intercalate into the clay comfortably, while larger surfactants (G2 and G3) are expected to form frustrated intercalated structures due to the location and depth of the free energy minima. This would agree with the previous observations. As primary steps to understand the Ab protein behavior under biological conditions, simulations of bulk water and hydrated lipids were performed and the results were compared with the literature. Hydrated lipids were simulated using a full atomistic model of lipids (dipalmitoylphosphatidylcholine) and water with a cvff force-field and it was found that structural properties such as the molecular head group area and membrane thickness were accurately produced with MD simulation. Systems of the protein Ab(1-42) in bulk water were simulated and some secondary structural change, with loss of part of the a-helical structure, occurred during the 1 ns of simulation time at 323K. The fragment Ab(31-42) with b-sheet conformation was also simulated in bulk water, and the extended b-sheet structure became a bent structure. Simulations of Ab(1- 42) or Ab(31-42) near lipid bilayers have been performed to investigate the structural property changes under biological conditions. The different nature of structural change was observed from the simulations of the protein or fragment in water and near lipid bilayers due to the different solvent environment. The protein has close contacts with the membrane surface. It was impossible to observe the conformational change to b-sheet and protein entrance into the lipid bilayer within 1 ns simulations.

The biodegradation kinetics of Geropon TC-42 (trademark) by an acclimated culture was investigated in anoxic batch reactors to determine biokinetic coefficients to be implemented in two biofilm mathematical models. Geropon TC-42 (trademark) is the surfactant commonly used in space habitation. The two biofilm models differ in that one assumes a constant biofilm density and the other allows biofilm density changes based on space occupancy theory. Extant kinetic analysis of a mixed microbial culture using Geropon TC-42 (trademark) as sole carbon source was used to determine cell yield, specific growth rate, and the half-saturation constant for S0/X0 ratios of 4, 12.5, and 34.5. To estimate cell yield, linear regression analysis was performed on data obtained from three sets of simultaneous batch experiments for three S0/X0 ratios. The regressions showed non-zero intercepts, suggesting that cell multiplication is not possible at low substrate concentrations. Non-linear least-squares analysis of the integrated equation was used to estimate the specific growth rate and the half-saturation constant. Net specific growth rate dependence on substrate concentration indicates a self-inhibitory effect of Geropon TC-42 (trademark). The flow rate and the ratio of the concentrations of surfactant to nitrate were the factors that most affected the simulations. Higher flow rates resulted in a shorter hydraulic retention time, shorter startup periods, and faster approach to a steady-state biofilm. At steady-state, higher flow resulted in lower surfactant removal. Higher influent surfactant/nitrate concentration ratios caused a longer startup period, supported more surfactant utilization, and biofilm growth. Both models correlate to the empirical data. A model assuming constant biofilm density is computationally simpler and easier to implement. Therefore, a suitable anoxic packed bed reactor for the removal of the surfactant Geropon TC-42 (trademark) can be designed by using the estimated kinetic values and a model assuming constant biofilm density.

Recently there has been a great deal of attention in the oilfield industry focused on the phenomenal properties of viscoelastic surfactants (VES). The interest is motivated by their applications as switchable smart fluids, their surface tension, and their thickening and rheology enhancement in aqueous solution. Surfactant molecules in solution are known for their ability to assemble spontaneously into complex structures. Under certain thermodynamic conditions, temperature and electrolyte concentrations, wormlike micelles are formed. These micelles share similar equilibrium and dynamic properties with polymer solutions, However, micellar chains can break and recombine spontaneously which make them part of the more general class of living polymers. It is vital to understand the properties of viscoelastic wormlike micelles with regard to their flow in porous media. The overall objective of this study is to establish a better understanding of counterion effect on behavior of VES. The dependence of macroscopic properties on intermolecular interactions of complex fluid systems such as VES is an enormous challenge. To achieve our objective, we use first-principle calculations and molecular dynamics (MD) simulations to resolve the full chemical details in order to study how the structure of the micellar and solution properties depends on the chemical structure of the surfactant head group (HG) and type of counterion. In particular, we run simulations for different structures in gas-phase and aqueous solutions together with their salt counterions at room temperature and atmospheric pressure. For this purpose, we consider four types of surfactant HG (anionic, cationic, betaine and amidoamine oxide) together with the most common ions present in the acidizing fluid of a carbonate reservoir such as Ca2+, Mg2+, Fe2+, Fe3+, Mn2+ and Zn2+, Cl-, OH- and HS-. Hydration of ions as well as interactions with surfactant the HG are studied using density functional theory (DFT). The results give important insight into the links between molecular details of VES HG structure and observed solution properties. This study proposes for the first time the possible mechanisms that explain the exotic behavior of VES at high Fe(III) concentration. Also, our MD simulation suggests that distribution of chloride ion around surfactant molecules is responsible for their viscosity behavior in HCl solution. We believe that our results are an important step to develop more systematic procedures for the molecular design and formulation of more effective and efficient VES systems.

The objectives of this study are to synthesize sub-micron sized zinc borate and to use them with other flame retardant additives in poly(ethylene terephthalate) (PET) based composites. The study can be divided into two parts. In the first part, it was aimed to synthesize sub-micron sized zinc borate (2ZnO.3B2O3.3.5H2O) with the reaction of zinc oxide and boric acid. For this purpose, low molecular weight additives or surfactants were used in the syntheses to prevent the agglomeration and to decrease particle size. Effect of type of surfactant and its concentration / effect of using nano-sized zinc oxide as reactant on the synthesis, properties and morphology of 2ZnO.3B2O3.3.5H2O were investigated. Synthesized zinc borates were characterized by X-Ray diffraction (XRD), Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The results were compared with a commercial zinc borate, Firebrake (FB). Characterization results showed that at least in one dimension sub-micron size was obtained and synthesized zinc borates did not lose their hydration water until the process temperature of the composites. In the second part of the study, PET based composites, which mainly included synthesized sub-micron sized zinc borates were prepared by using a co-rotating twin screw extruder and injection molding machine. Synergist materials such as boron phosphate (BP) and triphenyl phosphate (TPP) were also used in the composite preparation. The composites were characterized in terms of flammability and mechanical properties. Flammability of composites was determined by using a Limiting Oxygen Index (LOI) test. Mechanical properties such as tensile strength, elastic modulus, elongation at break and impact strength were also studied. According to LOI and impact tests, the composites containing 3 wt. % BP and 2 wt. % zinc borate which was modified with poly(styrene-co-maleic anhydride), 2PSMA05/3BP and 2PSMA1/3BP have higher LOI and impact values when compared to neat PET.

Thermal behavior and molecular packing of alkylated poly(ethylene- alt- maleic anhydride) and poly(styrene-alt-maleic anhydride) were studied by means of differential scanning calorimetry, thermogravimetry, polarizing optical microscopy, and X-ray diffraction. Effects of the length and graft density of alkyl side chains and backbone rigidity on the thermal behavior and on the structure of the mesophases are discussed.

Solid-state complexes between diblock copolymer and amphiphilic surfactant (surf) results in polymers characterized by two length scales with one macroscopic ¡§block copolymer length¡¨ and one mesomorphic ordered ¡§nanoscale¡¨. In this study, the desired polymer was prepared by complexing the surf molecules, i.e., 4-dodecylbenzenesulfonic acid (DBSA), with polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) and a comb-coil A-block-(B-graft-C) type copolymer can be generated through a supramolecular assembly route. On the block copolymer scale, the PS blocks are phase-separation from the P4VP(DBSA)x block, which x denotes the molar ratio between DBSA and pyridine groups. Bonding interaction between PS-b-P4VP and DBSA was conformed by FTIR. PLM was used to detect the mesomorphic structure within P4VP(DBSA)x block. In all cases, we found that birefringent can be only found in copolymer with their comb content exceeding 63 wt%. In the thermal analysis, shows us that the glasses transition temperature(Tgs) of the P4VP(DBSA)x block increases with the increasing DBSA content, a result related to the stiffening of the P4VP main chain due to dense packing. On the mesomorphic nanoscale, wide-angle X-ray diffraction study suggests an ordered supramolecular layer structure was formed in most of the complexation cases, in which the thicknesses of the polymer and surf layers were determined from the one-dimensional correlation function. The result indicates that both layers thickness increase with increasing DBSA amounts due to the stretching of the long alkyl tail in DBSA. Finally, macroscopic morphology varied with the DBSA content according to TEM results.

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The industrial solvent trichloroethylene (TCE) and petroleum hydrocarbons (e.g., fuel oil) are among the most ubiquitous organic compounds found in subsurface contaminated environment. The developed treatment train system included the first stage of groundwater and surfactant flushing followed by the second stage of chemical oxidation such as potassium permanganate (KMnO4) and Fenton-like treatment. The third stage was the application of enhanced bioremediation for the further removal of residual contaminants after the first two treatment processes. The objectives of this study were to (1) assess the applicability of treatment train system for the remediation of organic compounds contaminated subsurface environment, (2) determine the optimal operational conditions of the three-stage treatment system, and (3) evaluate the effects of residual surfactant Simple GreenTM (SG) and hydrogen peroxide (H2O2) after chemical oxidation stage on the efficiency of bioremediation process. In this study, three different surfactants [SG, Triton X-100, and Tween 80] were evaluated in batch experiments for their feasibility on contaminants removal. Results from the surfactant biodegradation and microbial enumeration study indicate that SG was more biodegradable and was able to enhance the microbial activity of the intrinsic microorganisms. Thus, SG was applied in the following batch or column experiments of the treatment train system. Results from this study indicate that approximately 87.6% of TCE in the system (with initial concentration of 40 mg L-1) could be removed from the simulated dense non-aqueous-phase liquids (DNAPLs) system after groundwater flushing followed by biodegradable surfactant (1 g L-1 of SG) flushing, while the TCE concentrations dropped from 40 to 4.96 mg L-1 at the end of the flushing experiment. Moreover, approximately 10.7% of the remaining TCE could be removed from the system after the oxidation process using KMnO4 as the oxidant. Results from the oxidation process show that TCE was reduced from 4.96 to 0.69 mg L-1, and chloride concentation was increased from ND to 0.88 mg L-1 with the presence of 1 g L-1 of SG. The residual 1.7% of the TCE could be further remediated via the enhanced bioremediation stage, and the TCE concentrations dropped from 0.69 mg L-1 to below detection limit at the end of the bioremediation experiment. Results also indicate that the remaining KMnO4 had no significant inhibition on bacterial growth and TCE biodegradation. Thus, SG flushing and KMnO4 oxidation would not cause adverse effect on subsequent bioremediation process using intrinsic bacteria. Thus, complete TCE remediation was observed in this study using the three-stage treatment scheme. Results from the column experiment reveal that a complete TPH removal could be obtained after the application of three consecutive treatment processes. Results show that TPH concentration could be reduced from 50,000 mg kg-1 to below detection limit. This indicates that the treatment train system is a promising technology to remediate fuel-oil contaminated soils. Results from the column study indicate that approximate 80.3% of initial TPH in the soil could be removed after the SG [50 pore volumes (PVs)] followed by groundwater (30 PVs) flushing. The Fenton-like oxidation (with 6% of H2O2 addition) was able to remove another 15.0% of TPH. The observed first-order reaction rate constant of TPH oxidation was 2.74¡Ñ10-2 min-1, and the half-life was 25.3 min during the first 40 min of reaction. The residual 4.7% of the TPH could be further remediated via the aerobic bioremediation process. Thus, complete TPH removal was obtained in this study using the three-stage treatment scheme. The proposed treatment train system would be expected to provide a more efficient and cost-effective alternative to remediate chlorinated solvent and petroleum hydrocarbons contaminated sites.

Intrinsically conducting polymers (ICPs) with high mechanical strength and electrical conductivity are attractive for several applications spanning the fields of energy, defense, and transportation. Electrochemically processed polythiophene (PTh) films are a class of ICPs that have been demonstrated recently to possess electrical conductivities as high as 1,300 S/cm and be stronger than common types of processed aluminum foils. While these results are promising, the electrical conductivity of PTh is still low compared to metals and the effects of important process conditions such as electrode resistance, distance between working and counter electrodes, and thiophene concentration on the structure and physical properties of electrochemically processed PTh films must be investigated in detail. In this work, electrode resistance and inter-electrode distance were demonstrated to be inversely proportional to the charge efficiency for PTh film growth. A critical concentration of thiophene that produced films with the highest conductivity was also revealed. Anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodeclybenzene sulfonate (SDBS) were used, with and without a proton scavenger, in the Lewis acid boron trifluoride diethyl etherate (BFEE) electrolyte, which allows polymerization of thiophene at low oxidation potentials, to enhance the ordering and conjugation length of PTh through stabilization of the radical cation of thiophene via the dodecyl chain of the anionic surfactants. X-ray diffraction spectra revealed enhanced order and packing when surfactant was used during the processing of PTh films, and measured electrical conductivities were increased by as much as 300% because of the surfactant-mediated structural improvements. Necking behavior observed in tensile test of PTh films with anionic surfactant additives also suggests chain alignment and increased chain length.