Indiana University-Purdue University Indianapolis (IUPUI) / The C-O single bond is found in numerous functional motifs including carboxylic acids, alcohols, and ethers. These compounds represent ideal precursors towards C-X (X = C, H, or heteroatom) bond formation due to their inherent stability and abundance in nature. As such, synthetic chemists continue to develop new technologies for the transformation of these precursors into biologically useful targets such as amides and amines. However, due to the stability of the C-O single bond, accessing such targets remains a consistent challenge. The activation of the carboxylic acids towards peptide synthesis has been facilitated through various coupling agents, including organoboron and transition metal catalysts. However, coupling agents can generate stochiometric, difficult-to-remove, toxic waste by-products. Organoboron/transition metal catalyzed condensations offer a more atom economical approach but suffer from varying degrees of optical erosion and poor sustainability. Phosphonium-based deoxyaminative technologies provide access to amines from alcohols via a phosphorus oxygen double bond formation driving force, but possesses a narrow nucleophilic nitrogen source scope, and poor atom economy. Transition metal/enzyme catalyzed “hydrogen borrowings” represent atom economical deoxyaminative alternatives. Still, their respective use of costly metals, and multiple enzymatic cascade steps severely limit the sustainability and scope of such protocols. An ambient deoxyamidation of carboxylic acids and deoxyamination of alcohols was developed through the use of N-haloimides activated by triphenylphosphine. Such technologies were found to possess broad functional tolerance and formed C-N bonds via a coupling to free amines, and the direct installment of the imide motif. Mechanistic experiments suggest that such transformations take place via the in situ generation of two separate phosphonium reactive species.

<p>The C-O single bond is found in numerous functional motifs including carboxylic acids,</p> <p>alcohols, and ethers. These compounds represent ideal precursors towards C-X (X = C, H, or heteroatom) bond formation due to their inherent stability and abundance in nature. As such, synthetic chemists continue to develop new technologies for the transformation of these precursors into biologically useful targets such as amides and amines. However, due to the stability of the C-O single bond, accessing such targets remains a consistent challenge. The activation of the carboxylic acids towards peptide synthesis has been facilitated through various coupling agents, including organoboron and transition metal catalysts. However, coupling agents can generate stochiometric, difficult-to-remove, toxic waste by-products.</p> <p>Organoboron/transition metal catalyzed condensations offer a more atom economical approach but suffer from varying degrees of optical erosion and poor sustainability. Phosphonium-based deoxyaminative technologies provide access to amines from alcohols via a phosphorus oxygen double bond formation driving force, but possesses a narrow nucleophilic nitrogen source scope, and poor atom economy. Transition metal/enzyme catalyzed “hydrogen borrowings” represent atom economical deoxyaminative alternatives. Still, their respective use of costly metals, and multiple enzymatic cascade steps severely limit the sustainability and scope of such protocols.</p> <p>An ambient deoxyamidation of carboxylic acids and deoxyamination of alcohols was</p> <p>developed through the use of N-haloimides activated by triphenylphosphine. Such</p> <p>technologies were found to possess broad functional tolerance and formed C-N bonds via a</p> <p>coupling to free amines, and the direct installment of the imide motif. Mechanistic experiments suggest that such transformations take place via the in situ generation of two separate phosphonium reactive species. </p>

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This thesis focuses on understanding the factors that affect the properties of polyetherimide (PEI) and improving the properties. As a high-performance thermoplastic resin, the first challenge in PEI application is its high processing temperature and viscosity. Therefore, two supramolecular strategies were applied to not only solve the problem of high processing temperature or viscosity but also enhance the mechanical and flame retardancy. In addition, the yellow to amber color of PEIs limits its applications in high-tech fields such as microelectronics and optoelectronics. Thus, a fundamental study of how end group and molecular weight affect the optical properties of PEIs provides a better knowledge of the mechanism and an effective strategy for designing PEIs. To lower the processing viscosity while maintaining or even improving the mechanical properties of PEI, the first strategy was to synthesize PEI oligomers, and incorporate self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at the chain ends. Surprisingly, the UPy imparted PEI with a Mn as low as 8 kDa (8k-PEI) with great film formability. Excitingly, 8k-PEI-UPy exhibited an outstanding Young's modulus higher than those of state-of-the-art high-molecular-weight (high-MW) commercial PEIs. Therefore, the incorporation of UPy was proved to be an effective method to synthesize low-molecular-weight, high-mechanical-strength PEIs. Although low-molecular-weight PEI-UPy had high mechanical properties, its limited thermal stability and potentially low flame retardancy, however, restricted its applications in areas such as aerospace and aircrafts. Hence in another strategy, which utilize the phosphonium ionic groups were incorporated into PEI oligomers targeting at achieving high thermal stability, flame retardancy, and mechanical properties simultaneously. Functionalization of dianhydride-terminated PEI by tetraphenylphosphonium bromide afforded the synthesis of phosphonium bromide terminated PEI (PEI-PhPPh3Br), which simultaneously exhibited excellent thermal stability up to ~400°C, outstanding flame retardancy evidenced by high char yield and extremely high limiting oxygen index, and a very high mechanical strength. The study thus provides an efficient strategy to simultaneously enhance the thermal and mechanical properties as well as flame retardancy. Furthermore, the low-molecular-weight PEI-PhPPh3Br had good processability due to its strong shear thinning. In addition to the thermal and mechanical properties and flame retardancy, the end groups affect the optical properties, especially the yellowness, of PEIs. Understanding how end group and molecular weight affect the yellowness, of PEIs is critical for their applications in fields including optoelectronics and microelectronics. Thereby, PEIs with different Mn and various end groups including electron-withdrawing and electron-donating were prepared and characterized. Electron-withdrawing end groups reduced the yellowness and increased the transparency of PEI, regardless of the Mn. Electron-donating end groups increased the yellowness of PEIs with dependence on the Mn. The Mn affected the yellowness of PEIs by changing end group density and the probability of charge-transfer complex formation. The systematic study reveals the correlations among yellowness, end group, and molecular weight of PEIs. / MS / One small step for end groups, one giant leap for properties. Simply tuning the repeating units at the polymer chain ends drastically changes the properties of the polymers. This thesis focuses on the modification of the end groups in low-molecular-weight polyetherimides, a class of high-temperature high-performance engineering thermoplastics, to achieve improved and tunable properties, such as mechanical strength, flame retardancy, and optical properties. On one hand, low-molecular-weight polyetherimides enabled low processing temperatures to decrease the processing cost. On the other hand, the incorporation of noncovalent hydrogen bonding interactions improved the mechanical strength of low-molecular-weight polyetherimides and maintained their thermal stability. This study for the first time showed the incorporation of multiple hydrogen bonds was effective to generate low-molecular weight but high-mechanical-strength polyetherimides. Although multiple hydrogen bonds improved the mechanical properties of polyetherimides, the thermal stability was inadequate for industrial melt processing at elevated temperatures. Alternatively, by incorporating noncovalent electrostatic interaction groups, the polyetherimides showed not only improved mechanical properties but also high thermal stability. Excitingly, their flame retardancy and melt processability were also significantly improved. This polyetherimide has great potential for applications such as aircrafts and aerospace. The end groups affected not only the thermal, mechanical, and rheological properties, but also the optical properties of polyetherimide. Polyetherimide has an intrinsic yellow color originated from the charge transfer complexes that are formed between electron-rich and electron-deficient moieties in the polymer chains. By tuning the concentrations of the different end groups, we controlled the strength of the charge transfer complexes and thus the yellowness of the films. Through a systematic study, a 3D contour was constructed and revealed the relations among the yellowness, the end group, and the molecular weight of polyetherimides. The 3D contour provides guidelines for designing polyetherimides with suitable molecular weights and adequately low yellowness.

This thesis describes the synthesis and characterisation of phosphonium aryloxides, amides and phosphides. These compounds have been formed via the deprotonation of organic acids [of the type ROH, and R(_2)X, where X = NH, PH, R = aryl group] by basic phosphonium ylidic species [R(_3)PX, X = CH(_2,) C(Me)H, C(Ph)H, NH] in mixtures of hydrocarbon (toluene) and/or polar (acetonitrile, thf) solvents. All of these compounds contain both acidic CHs and 'naked' anions which promote extensive hydrogen bonding. Chapter 1 provides an outline of the fields of ylidic chemistry and hydrogen bonding. In Chapter 2, general experimental methods are described. Chapter 3 records all experimental results pertaining to this work. Here preparation of starting materials is documented, followed by an account of the synthesis and characterisation of twenty-three compounds. For all compounds melting point measurements, (^1)H NMR, (^31)P NMR, infrared spectra, and elemental analysis are recorded. Discussion of these results is documented in Chapters 4 to 7. Where possible, solid-state structures for compounds obtained by single crystal X-ray diffraction (nineteen structures) and single crystal neutron diffraction (two structures) are included. Chapter 4 discusses simple phosphonium aryloxide salts, while Chapter 5 is concerned with related phosphonium amides and phosphides. Chapter 6 deals with an extension of this work involving multifiinctional organic acids. Finally, Chapter 7 discusses unexpected results resulting from the work described in Chapter 6.

An unprecedented comprehensive study of ammonium and phosphonium polyelectrolytes probed and examined structure-property relationships with a focus on different macromolecular properties. Conventional free radical polymerization readily generated a large library of ammonium- and phosphonium-containing polyelectrolytes. Along with the two different cationic atoms, the alkyl substituent lengths and counterions were varied to generate a thorough structure-property relationship analysis. Phosphonium macromolecules displayed improved thermal stabilities and improved ionic conductivities compared to ammonium analogs. Longer alkyl substituent lengths systematically decreased the glass transition temperatures of all polyelectrolytes; the larger, bulkier counterions also resulted in lower glass transition temperatures. Counterion also impacted the thermal stability of the polymerized ionic liquids with less basic counterions leading to improved thermal stability. For the first time, the efficacy of phosphonium macromolecules for nonviral nucleic acid delivery was examined. Phosphonium macromolecules more efficiently complexed nucleic acids than ammonium analogs and butyl-containing phosphonium macromolecules delivered nucleic acids more effectively than the ammonium analog. Controlled radical polymerization generated unprecedented phosphonium-containing diblock copolymers and these diblock copolymers displayed enhanced colloidal stability and lower cytotoxicity compared to the phosphonium homopolymer for nucleic acid delivery. Step-growth polymerization techniques enabled the synthesis of well-defined, high molecular weight phosphonium ionenes for the first time. Phosphonium ionenes exhibited higher thermal stability and alkaline stability compared to ammonium ionenes. Due to their high thermal stability and relatively low glass transition temperatures, unprecedented melt rheology studies on polyelectrolytes probed the melt flow characteristics of phosphonium ionenes. Novel phosphonium gemini surfactants displayed interesting solution properties in aqueous and chloroform solutions. Electrospinning of the phosphonium gemini surfactants created uniform fibers. The synthesis and characterization of sulfonium polyelectrolytes enabled the first examination of sulfonium macromolecules for nonviral nucleic acid delivery. Sulfonium polyelectrolytes successfully bound nucleic acids and delivered them in vitro. Controlled radical polymerization generated innovative AB diblock and ABA triblock copolymers that displayed salt- and temperature-responsive properties suitable for biological applications such as drug delivery vehicles and hydrogels. Finally, adenine-containing polyelectrolytes were synthesized and they were successfully electrospun to generate adenine-decorated nanofibers appropriate for filtration and nonwoven applications. / Ph. D.

New phosphonium and ammonium ionic liquids were prepared for use in two green applications. Ionic liquids are generating considerable current interest as media for electrochemical processes such as electrodeposition, which can be used to create thin films of a variety of compounds. For the first time, silicon deposition has been achieved in the phosphonium ionic liquid triethyl(2-methoxyethyl)phosphonium bis(trifluoromethylsulfonyl)amide (P201-TFSI). Subsequently, silicon has been deposited from a wide variety of precursors in order to optimize the thickness and morphology of the deposited films. The silicon films electrodeposited in the phosphonium ionic liquid show marked differences from those deposited in organic solvents, imidizolium and pyrrolidinium based ionic liquids. Phosphonium and ammonium ionic liquids were also investigated for use in carbon dioxide capture. Task-specific ionic liquids have shown great promise as agents for the physisorption and chemisorption of CO2 from combustion gas streams. Efforts to synthesize new task specific ionic liquids with multiple amine functionalities for CO2 capture are reported. Four different reaction pathways were explored for the synthesis of these materials. While this goal was not achieved in this work, task-specific phosphonium and ammonium ionic liquids offer the promise of opening up new areas in ionic liquid research. / text

Ionic liquids (ILs) were studied as solvents for electrochemical reactions with the intent to devise metallurgical processes for Al, Mg and Ti that are less energy intensive and operate at lower temperatures than current industrial practice. Tetra-alkyl phosphonium ILs are on the low end of the IL cost spectrum and are regarded as understudied compared with imidazolium and pyridinium ILs. They are also known to be more thermally stable. The density, viscosity and conductivity of the phosphonium ILs and metal salt-IL mixtures were measured. The conductivity of the phosphonium ILs tested were found to be roughly an order of magnitude lower than imidazolium ILs; this is attributed to the relatively large cation size and localized charge. Linear density-temperature functions are presented. The viscosity and conductivity temperature relationship was modeled using the Vogel-Tamman-Fulcher (VTF) equation. The electrochemical window of A10341'14,6,6,610 was studied on a Pt substrate over a wide range of A1C13 concentrations using cyclic voltammetry (CV). It was found that the tetra-alkyl phosphonium cation is on the order of 800 mV more electrochemically stable than the 1-ethyl-3-methyl imidazolium (EMI+). Cathodic and anodic polarization of Al in A1C13-[P14,6,6,6]C1 (Xmc13 = 0.67) was studied at temperatures ranging from 347 to 423 K. The Butler-Volmer equation was fitted to the plots by varying the kinetic parameters. The cathodic reaction was found to be diffusion limited and the anodic reaction is limited by passivation at lower temperatures. The overpotential required for electrodissolution of Al was found to be higher than for electrodeposition. Aluminium was electrodeposited using both an electrowinning setup (chlorine evolution anode reaction) and electrorefining setup (Al dissolution anode reaction). The deposits were characterized in terms of morphology, current efficiency and power consumption. A variety of deposit morphologies were observed ranging from smooth, to spherical to dendritic, and in some cases, the IL was occluded in the deposit. The current efficiency and power consumption were negatively impacted by the presence of H2O and HCl present in the as-received ILs and by C12(g) generated by the anode reaction in the case of the electrowinning setup. HC1 was removed by cyclic polarization or corrosion of pure Al, resulting in current efficiencies above 90%. Aluminium was electrodeposited using the electrorefining setup with anode-cathode spacing of 2 mm at power consumption as low as 0.6 kWhr/kg-Al. This is very low compared with industrial Al electrorefining and Al electroplating using the National Bureau of Standards bath, which require 15-18 kWhr/kg-Al and 18 kWhr/kg-Al, respectively. However, due to low solution conductivity the power consumption increases significantly with increased anode-cathode spacing. Titanium tetrachloride was found to be soluble in [P14,6,6,6]Cl and increases the conductivity of the solution. Attempts to reduce the Ti(IV) included corrosion of titanium metal, corrosion of magnesium metal powder and cathodic polarization. Despite a few attempts, the electro-deposition of Ti was not observed. At this point, titanium electrodeposition from phosphonium based ILs does not appear feasible.

Ionic liquids (ILs) were studied as solvents for electrochemical reactions with the intent to devise metallurgical processes for Al, Mg and Ti that are less energy intensive and operate at lower temperatures than current industrial practice. Tetra-alkyl phosphonium ILs are on the low end of the IL cost spectrum and are regarded as understudied compared with imidazolium and pyridinium ILs. They are also known to be more thermally stable. The density, viscosity and conductivity of the phosphonium ILs and metal salt-IL mixtures were measured. The conductivity of the phosphonium ILs tested were found to be roughly an order of magnitude lower than imidazolium ILs; this is attributed to the relatively large cation size and localized charge. Linear density-temperature functions are presented. The viscosity and conductivity temperature relationship was modeled using the Vogel-Tamman-Fulcher (VTF) equation. The electrochemical window of A10341'14,6,6,610 was studied on a Pt substrate over a wide range of A1C13 concentrations using cyclic voltammetry (CV). It was found that the tetra-alkyl phosphonium cation is on the order of 800 mV more electrochemically stable than the 1-ethyl-3-methyl imidazolium (EMI+). Cathodic and anodic polarization of Al in A1C13-[P14,6,6,6]C1 (Xmc13 = 0.67) was studied at temperatures ranging from 347 to 423 K. The Butler-Volmer equation was fitted to the plots by varying the kinetic parameters. The cathodic reaction was found to be diffusion limited and the anodic reaction is limited by passivation at lower temperatures. The overpotential required for electrodissolution of Al was found to be higher than for electrodeposition. Aluminium was electrodeposited using both an electrowinning setup (chlorine evolution anode reaction) and electrorefining setup (Al dissolution anode reaction). The deposits were characterized in terms of morphology, current efficiency and power consumption. A variety of deposit morphologies were observed ranging from smooth, to spherical to dendritic, and in some cases, the IL was occluded in the deposit. The current efficiency and power consumption were negatively impacted by the presence of H2O and HCl present in the as-received ILs and by C12(g) generated by the anode reaction in the case of the electrowinning setup. HC1 was removed by cyclic polarization or corrosion of pure Al, resulting in current efficiencies above 90%. Aluminium was electrodeposited using the electrorefining setup with anode-cathode spacing of 2 mm at power consumption as low as 0.6 kWhr/kg-Al. This is very low compared with industrial Al electrorefining and Al electroplating using the National Bureau of Standards bath, which require 15-18 kWhr/kg-Al and 18 kWhr/kg-Al, respectively. However, due to low solution conductivity the power consumption increases significantly with increased anode-cathode spacing. Titanium tetrachloride was found to be soluble in [P14,6,6,6]Cl and increases the conductivity of the solution. Attempts to reduce the Ti(IV) included corrosion of titanium metal, corrosion of magnesium metal powder and cathodic polarization. Despite a few attempts, the electro-deposition of Ti was not observed. At this point, titanium electrodeposition from phosphonium based ILs does not appear feasible.

Ionic liquids (ILs) were studied as solvents for electrochemical reactions with the intent to devise metallurgical processes for Al, Mg and Ti that are less energy intensive and operate at lower temperatures than current industrial practice. Tetra-alkyl phosphonium ILs are on the low end of the IL cost spectrum and are regarded as understudied compared with imidazolium and pyridinium ILs. They are also known to be more thermally stable. The density, viscosity and conductivity of the phosphonium ILs and metal salt-IL mixtures were measured. The conductivity of the phosphonium ILs tested were found to be roughly an order of magnitude lower than imidazolium ILs; this is attributed to the relatively large cation size and localized charge. Linear density-temperature functions are presented. The viscosity and conductivity temperature relationship was modeled using the Vogel-Tamman-Fulcher (VTF) equation. The electrochemical window of A10341'14,6,6,610 was studied on a Pt substrate over a wide range of A1C13 concentrations using cyclic voltammetry (CV). It was found that the tetra-alkyl phosphonium cation is on the order of 800 mV more electrochemically stable than the 1-ethyl-3-methyl imidazolium (EMI+). Cathodic and anodic polarization of Al in A1C13-[P14,6,6,6]C1 (Xmc13 = 0.67) was studied at temperatures ranging from 347 to 423 K. The Butler-Volmer equation was fitted to the plots by varying the kinetic parameters. The cathodic reaction was found to be diffusion limited and the anodic reaction is limited by passivation at lower temperatures. The overpotential required for electrodissolution of Al was found to be higher than for electrodeposition. Aluminium was electrodeposited using both an electrowinning setup (chlorine evolution anode reaction) and electrorefining setup (Al dissolution anode reaction). The deposits were characterized in terms of morphology, current efficiency and power consumption. A variety of deposit morphologies were observed ranging from smooth, to spherical to dendritic, and in some cases, the IL was occluded in the deposit. The current efficiency and power consumption were negatively impacted by the presence of H2O and HCl present in the as-received ILs and by C12(g) generated by the anode reaction in the case of the electrowinning setup. HC1 was removed by cyclic polarization or corrosion of pure Al, resulting in current efficiencies above 90%. Aluminium was electrodeposited using the electrorefining setup with anode-cathode spacing of 2 mm at power consumption as low as 0.6 kWhr/kg-Al. This is very low compared with industrial Al electrorefining and Al electroplating using the National Bureau of Standards bath, which require 15-18 kWhr/kg-Al and 18 kWhr/kg-Al, respectively. However, due to low solution conductivity the power consumption increases significantly with increased anode-cathode spacing. Titanium tetrachloride was found to be soluble in [P14,6,6,6]Cl and increases the conductivity of the solution. Attempts to reduce the Ti(IV) included corrosion of titanium metal, corrosion of magnesium metal powder and cathodic polarization. Despite a few attempts, the electro-deposition of Ti was not observed. At this point, titanium electrodeposition from phosphonium based ILs does not appear feasible. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate