Additive manufacturing provides unmatched control and diversity over structural design of polymeric, ceramic and metallic parts. Nevertheless, until recently, the toolbox of polymeric feedstocks for light based additive manufacturing limited employment of printed parts for applications necessitating high thermomechanical performance. Development of synthetic pathways permitted the first additive manufacturing of high performance poly(amide imides) via ultraviolet assisted direct ink write (UV-DIW) printing. Precursor resins exhibited prerequisite rheology and reactivity for UV-DIW and produced organogels were well-defined and self-supporting. Thermal treatment induced drying and imidization of the precursor organogels to form the desired poly(amide imide) structures. During post-processing the parts displayed linear isotropic shrinkage as low as 26% and exhibited competitive thermomechanical properties. Following expansion of the high performance backbones available for additive manufacturing, simplification of synthetic rigors was undertaken. This investigation facilitated the evolution of the first photocurable and processable small molecule polyimide precursors. These supramolecular carboxylate ammonium nylon salts, coined polysalts, allowed for additive manufacturing of both high performance polyimides and polyetherimides using vat photopolymerization (VP). The use of small molecule precursors over previously investigated polymeric precursors displayed much lower solution viscosities yielding reduction of organic solvent loading, inducing lower overall shrinkage. Polysalts provide a stimulating platform for rapid and facile printing of high performance polyimides in the future. Surveying the excellent carbonization behavior for aromatic polyimides spurred translation of known 2D protocols to post-processing of printed polyimides. Applying pyrolysis methodologies to parts produced using VP and UV-DIW induced efficient carbonization at 1000 °C. Remarkably, the carbonized parts retained structure and did not display cracks or pore formation. Raman spectroscopy indicated production of disordered carbon via the utilized pyrolysis protocol, in line with literature on carbonization of PMDA-ODA polyimide at 1000 °C. Electrical testing indicated production of conductive materials following pyrolysis, with carbonization temperature modulating the performance. The excellent thermal stability, transport properties, and known mechanical performance of carbonaceous materials may enable application of these printed objects in customized electronics and aerospace environments. Exploration of drop-in monomeric units permitted a multi-pronged research program into augmentation of mechanical, rheological and transport properties of high performance polyetherimides (PEIs). Installation of sodium or lithium substituted disulfonated monomers via classical two-step polyimide synthesis afforded two series of sulfonated polyetherimides (sPEI). The sPEIs exhibited robust thermal properties, with high sulfonate mol% inducing Tg > 300 °C. X-ray scattering experiments revealed the development of domains via inclusion of the sulfonate moieties, with low mol% producing larger domain spacing. The larger domains present in the low mol% sPEIs yielded improved ionic liquid uptake within 2 d, yielding improved ionic conductivities at room temperature relative to high mol% samples. The observed conductivities indicated potential of the sPEIs as battery electrolytes, but further ionic liquid incorporation is required for competitive performance. Development of a poly(ethylene glycol) (PEG) bearing macromonomer facilitated synthesis of PEIs and PI graft copolymers. When coupled with 4,4'-(4,4'-isopropylidene-diphenoxy)diphthalic anhydride (BPADA) and meta-phenylene diamine (mPD), the PEG-grafted materials exhibited signs of phase mixing at low mol% incorporation of macromonomer, with a single observable Tg depressed from neat BPADA-mPD. Doping of the PEI-g-PEG with lithium salts allowed for production of polymeric films that displayed good ionic conductivities at room temperatures. Extension of the PEG macromonomer into fully aromatic PIs yielded phase separated materials even at modest loadings, >2.5 mol%. The formed PEG-g-PMDA-ODA contained thermally stable PI main-chains with thermally labile graft chains, which when thermally treated induced facile quantitative PEG removal. Remarkably, the thermally treated materials retained flexibility, even at >60 wt.% PEG removal. Further investigations aim to explore use of novel PEIs in energy storage as well as low density and dielectric materials. / Doctor of Philosophy / High performance polymers enjoy wide use in microelectronics and aerospace industries due to high thermal stability and excellent mechanical performance. However, processing restrictions hinder manufacturing of 3-dimensional objects of many high performance polymers suitable for extreme environments. Additive manufacturing, also known as 3D printing, has garnered attention in both academic and industrial settings over the last four decades due to the unmatched control over part design and internal structure, but the material arsenal for additive manufacturing of polymers lacks options for applications demanding high thermal stability. The first half of this dissertation aimed to promote translation of high performance polymeric chemistries to suitable feedstocks for additive manufacturing. By designing and developing novel chemical pathways, traditional processing limitations were circumvented and high performance polymers, such as poly(amide imides) and polyimides, were successfully processed via light based additive manufacturing. Likewise, by investigating carbonization dynamics of polyimides and expanding current additive manufacturing techniques for processing of fully aromatic polyimides, complex 3D carbonaceous materials were obtained. These carbon objects present extreme thermal stability and electrical conductivity, advantageous for aerospace and electronic industries. Additionally, investigations allowed for development of synthetically facile routes for expanding the available polyimide backbones for additive manufacturing via use of small molecule precursors. The second half of the dissertation explored novel polyetherimide and polyimide reagents for production of functional materials. Harnessing ionic building blocks permitted synthesis of a series of thermally robust polyetherimides displaying promise for energy storage. Similarly, coupling previous literature for ion conduction in solid polymer electrolytes for battery applications with thermally stable and flame resistant polyetherimides enabled synthesis of a series of innovative graft copolymers with good room temperature ionic conductivities. Lastly, pairing of thermally labile polymers with thermally resistant polyimide backbones allowed for development of an exciting platform for obtaining highly insulting and flexible films for electronics applications. Outlined future work aims to probe the formation of pores in the obtained polymer

Novel, high molecular weight poly(dimethylsiloxane) / cycloaliphatic polyester segmented copolymers were prepared and characterized. Specifically, polyesters based on dimethyl 1,4-cyclohexane dicarboxylate and 1,4-butanediol were employed. The copolymers were synthesized via a melt process using a high trans content isomer which afforded semi-crystalline morphologies. Aminopropyl terminated poly(dimethylsiloxane) oligonlers of controlled molecular weight were synthesized and then end capped with excess diester to form a diester terminated amide linked oligomer. The latter was then incorporated into the copolymer via melt transesterification step reaction segmented copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied to prepare a series of segmented polyester / poly(dimethylsiloxane) copolymers. / Ph. D.

The work presented in this dissertation revolves around the incorporation of t-butyl methacrylate into block copolymers utilizing anionic living polymerization techniques. The synthesis of t-butyl methacrylate/n-hexyl methacrylate and t-butyl methacrylate/2-ethylhexyl methacrylate di- and triblock copolymers was done by initiation with 2-methyl-1,1-diphenylpentyllithium in THF at -78°C by established techniques, and predictable molecular weights and narrow molecular weight distributions were obtained. Subsequent selective acid catalyzed hydrolysis of the t-butyl ester followed by neutralization with an appropriate base allowed the formation of block ioncontaining polymers. The synthesis of triblock polymers of t-butyl methacrylate with butadiene and styrene/butadiene systems and their analogous block ionomers was also carried out utilizing difunctional organolithium initiation of the hydrocarbon monomers in cyclohexane. For the polymerization of the tbma, it was found that the addition of large quantities of a polar solvent, such as THF, endcapping with diphenylethylene, and low temperatures (ca. -70 °C) were necessary to avoid side reactions which were theorized to be carbonyl attack by the dienyl- or styryllithium species. It was found that in the all methacrylic systems mentioned, when the t-butyl methacrylate blocks were in the ester form, i.e. not hydrolyzed to the acid or neutralized to the ionomer, the copolymers were phase mixed as evidenced by thermal analysis. Upon derivatization, however, the block polymers became phase separated. Morphological characterization of the block ionomers indicated that the morphology was dependent on both the ionic content and the ionic block length. Well defined, partially anisotropic, morphologies were observed by SAXS and TEM only in polymers that had both high ionic content and relatively large ionic block lengths. Elastomeric behavior was observed in copolymers with triblock architecture, but the materials degraded prior to plastic flow. On the other hand, all of the diene- and styrene/diene-methacrylates exhibited a multiphase morphology in the precursor state. Analogously to the all methacrylic system, the block ionomers were elastomeric, with the rubbery plateau extended ca. 60 °C relative to the non-ionic precursors. Crosslinking of the poly(butadiene) phase occurred at the onset of plastic flow, rendering the ionomers unable to be thermally processed. / The work presented in this dissertation revolves around the incorporation of t-butyl methacrylate into block copolymers utilizing anionic living polymerization techniques. The synthesis of t-butyl methacrylate/n-hexyl methacrylate and t-butyl methacrylate/2-ethylhexyl methacrylate di- and triblock copolymers was done by initiation with 2-methyl-1,1-diphenylpentyllithium in THF at -78°C by established techniques, and predictable molecular weights and narrow molecular weight distributions were obtained. Subsequent selective acid catalyzed hydrolysis of the t-butyl ester followed by neutralization with an appropriate base allowed the formation of block ioncontaining polymers. The synthesis of triblock polymers of t-butyl methacrylate with butadiene and styrene/butadiene systems and their analogous block ionomers was also carried out utilizing difunctional organolithium initiation of the hydrocarbon monomers in cyclohexane. For the polymerization of the tbma, it was found that the addition of large quantities of a polar solvent, such as THF, endcapping with diphenylethylene, and low temperatures (ca. -70 °C) were necessary to avoid side reactions which were theorized to be carbonyl attack by the dienyl- or styryllithium species. It was found that in the all methacrylic systems mentioned, when the t-butyl methacrylate blocks were in the ester form, i.e. not hydrolyzed to the acid or neutralized to the ionomer, the copolymers were phase mixed as evidenced by thermal analysis. Upon derivatization, however, the block polymers became phase separated. Morphological characterization of the block ionomers indicated that the morphology was dependent on both the ionic content and the ionic block length. Well defined, partially anisotropic, morphologies were observed by SAXS and TEM only in polymers that had both high ionic content and relatively large ionic block lengths. Elastomeric behavior was observed in copolymers with triblock architecture, but the materials degraded prior to plastic flow. On the other hand, all of the diene- and styrene/diene-methacrylates exhibited a multiphase morphology in the precursor state. Analogously to the all methacrylic system, the block ionomers were elastomeric, with the rubbery plateau extended ca. 60 °C relative to the non-ionic precursors. Crosslinking of the poly(butadiene) phase occurred at the onset of plastic flow, rendering the ionomers unable to be thermally processed. / Ph. D.

Multiblock [-A-B-]_n copolymers of bisphenol-A polycarbonate (I) and several poly(arylether sulfones) (II) have been investigated. The copolymers [see document for a diagram of copolymers (I) and (II)] were prepared from hydroxyl terminated oligomers (4,000 < M̅_n < 30,000) by an interfacial technique which utilized phosgene as the coupling agent. Characterization of the oligomers and copolymers included end group analysis, membrane osmometry, and gel permeation chromatography. One of the most interesting aspects of block copolymers is their ability to undergo microphase separation above a critical block length. Either one or two phase block copolymers can be prepared by controlling the molecular weights of the parent oligomers. In the bisphenol-A polycarbonate/bisphenol-A polysulfone system, for example, strictly one phase materials, with only one intermediate glass transition temperature, were obtained at block lengths of less than 10,000 g/mole. Two-phase copolymers resulted when blocks exceeding 20,000 g/mole were coupled. Copolymers comprised of intermediately sized blocks (M̅_n ≃16,000) could be obtained as either single or multiphase systems depending upon their previous thermal history. Homogeneous films, with a single intermediate Tg, were obtained via solution casting, whereas compression molding provided films exhibiting two Tg's. Subsequent DSC studies pointed out that microphase separation could be thermally, and irreversibly, induced by annealing above the Tg of the polysulfone blocks (190°C). Since polycarbonate and polysulfone are leading examples of tough, amorphous thermoplastics, the effects of microphase separation on the tensile, impact, and melt flow properties of the copolymers were investigated. A novel falling weight impact tester was designed and constructed to meet the needs of this study. The device was fully instrumented to provide a deceleration-time plot of the impact process by means of an accelerometer mounted in the projectile. Fracture energies for commercial homopolymers and graphite reinforced composites, in addition to polysulfone-polycarbonate block copolymers, were calculated from the impact curves. Both the tensile and impact properties of the copolymers improved with increasing polycarbonate content. Both single and multiphase materials were ductile and transparent as opposed to physical blends of the two. oligomers which were opaque and possessed poor mechanical properties. No differences due to microphase separation were observed in either the tensile or impact studies. The homogeneous copolymers displayed melt viscosities and activation energies nearly equal to those of the homopolymers. Much greater viscosities and activation energies were exhibited by the phase separated materials indicating that the heterogeneity was retained in the melt. / Ph. D.

Ion-containing macromolecules continue to stimulate new opportunities for emerging electro-active applications ranging from high performance energy devices to water purification membranes. Progress in polymer synthesis and engineering now permit well-defined, ion-containing macromolecules with tunable morphologies, mechanical performance, ion conductivity, and 3D structure in order to address these globally challenged technologies. Achieving tailored chemical compositions with high degrees of phase separation for optimizing conductivity and water adsorption remains a constant synthetic challenge and presents an exciting opportunity for engineering sophisticated macromolecular architectures. This dissertation will introduce unprecedented charged polymers using conventional free radical and anionic polymerization to incorporate ionic functionalities based on phosphonium cations. This new class of copolymers offers unique properties with ionic functionality for tailorable electro-active performance. / Ph. D.

Polymeric materials with inherent stimulus response represent an ever-growing area of research. In particular, block copolymers demonstrate exciting properties owing to their enhanced mechanical strength and microphase separation. Incorporating functionality into block copolymers proves useful in enhancing their utility. Presently, synthesis and subsequent post-polymerization modification achieved this for a range of block copolymers. In particular, neutralization of acid-containing polymers readily imparted ionic functionality and yielded microphase-separated block copolymer domains, enhancing polymer thermomechanical properties and ion transport. An ABA triblock copolymer composed of mechanically reinforcing polystyrene outer blocks and ionic central poly(1-methylimidazolium acrylate) block acted as a host for ionic liquid that caused an evolution in bulk morphology, resulting in enhanced ionic conductivity. The resulting membrane also exhibited a strong electromechanical actuation response under applied potential. Adding ionic liquid doped with a corresponding lithium salt enabled evaluation of sulfonated block copolymers as components of ternary polymer electrolytes, relevant for battery applications. Modification of a sulfonic acid-containing pentablock copolymer presented photocurable functional groups to the ionic domains which enabled their UV irradiation-induced curing. This novel route of modifying ion-containing block copolymers resulted in enhanced thermomechanical properties and enabled healing of physical defects in the film, unprecedented for ion-containing block copolymers. Covalent networks represent a relevant area of research for a wide variety of applications such as coatings, adhesives, and scaffolds. Careful design of degradable crosslinkers enables stimulus response in these networks by eliminating covalent crosslinks and affording a soluble product. Extension of poly(ethylene glycol) methacrylate-based network formation into three dimensions using microstereolithography resulted in novel acid-degradable 3D-printed parts. An additional study investigated mixtures of acrylamide-modified poly(vinyl alcohol) and poly(ethylene glycol) diacrylate as water-soluble resins for the direct formation of hydrogels from solution. Photorheology and photocalorimetry investigated the thermal and mechanical changes inherent in the curing process and evaluated the mixtures as a platform for microstereolithography. / Ph. D.

The research in this dissertation is focused on the synthesis and characterization of sterically crowded, precisely charged polyelectrolytes based on substituted stilbene comonomers. New sterically crowded polyelectrolytes based on functionalized stilbenes with maleic anhydride or functionalized N-phenylmaleimides were prepared via a "protected" precursor polymer strategy. The polyelectrolyte precursors readily dissolved in organic solvents and were characterized by 1H NMR, SEC, TGA, and DSC. The polyelectrolytes were obtained via simple deprotection chemistries. The use of different combinations of the donor-acceptor comonomer pairs and the alternating copolymerization of these comonomers lead to precise control over charge density and placement of charged groups along the polymer backbone. Analogous styrenic copolymers, for direct comparison to the stilbene structures, were also prepared. Broad peaks in 1H NMR spectra were observed. There were no thermal transitions measured by DSC below the degradation temperature. A strong polyelectrolyte effect, for both stilbene and styrene copolymers, occurred in deionized water and was suppressed by adding NaCl to the polymer solution. These results are not consistent with "rigid" rod polyelectrolytes in which chain collapse in the presence of added salt and chain expansion on dilution should not be observed. In response to these observations persistence length measurements were conducted on the stilbene and styrene copolymers to assess directly the steric crowding effect of added phenyl groups in stilbene copolymers. Both SEC and SAXS measurements were used to obtain persistence lengths. The results from three different approaches, Bohdanecký, graphical and Sharp and Bloomfield Global, were in good agreement. The persistence lengths of stilbene containing copolymers range from 3 to 6 nm and the added phenyl groups increase the rigidity of the polymer chain by about 30-50%. This puts these polymers into a broadly defined "semi-rigid" category of polymers and is consistent with the solution polyelectrolyte effect observed. In dilute solution characterization of stilbene containing polyanions, a 2-step dissociation behavior was observed for the two adjacent carboxylic acids in maleic acid containing polyanions. Stilbene polyanion solutions showed high Rh values in deionized water as shown by DLS measurements and a decrease of Rh values followed by aggregation upon gradual addition of salt. Bimodal peaks were observed in SEC measurements with the copolymer of 4-methylstilbene and maleic anhydride. DLS measurements indicated interchain aggregation as the origin of the apparent high molecular weight fraction. The antiviral activity of the polyanion based on sodium 4-styrenesulfonate and N-(4-sodium sulfophenyl)maleimide was found to be ~50 times higher than the microbicide, sodium poly(styrene sulfonate). The early study of antiviral activities of carboxylated stilbene and styrene polyanions also showed promising results. The synthesis of methyl sulfonate ester-functionalized polyanion precursors was attempted because they can be characterized without the complications caused by directly using charged sulfonate groups. / Ph. D.

Novel imidazole-containing polyelectrolytes based on poly(1-vinylimidazole) (poly(1VIM)) were functionalized with various hydroxyalkyl-substituents to investigate the influence of charge density and hydrogen bonding on nonviral DNA delivery.  Copolymers with higher charge densities exhibited increased cytotoxicity, whereas increased hydroxyl concentrations remained nontoxic.  DNA binding affinity increased with increased charge densities and increased hydroxyl content.  Dynamic light scattering determined the copolymers which delivered DNA most effectively maintained an intermediate binding affinity between copolymer and DNA.  Copolymers containing higher charge densities or hydroxyl concentrations bound DNA too tightly, preventing its release inside the cell.  Copolymers with lower charge densities failed to protect the DNA from enzymatic degradation.  Tuning hydrogen bonding concentration allowed for a less toxic and more effective alternative to conventional, highly charged polymers for the development of nonviral DNA delivery vehicles.  The synthesis of amine-containing imidazolium copolymers functionalized with low concentrations of folic acid enabled the investigation of additional polymer modifications on nonviral gene delivery.   Functionalization of 1VIM with various hydroxyalkyl and alkyl groups and subsequent conventional free radical polymerization afforded a series of imidazolium-containing polyelectrolytes.  Hydroxyl-containing homopolymers exhibited higher thermal stabilities and lower T_g's compared to the respective alkyl-analog.  X-ray scattering demonstrated the polarity of the hydroxyl group facilitated solvation of the electrostatic interactions disrupting the nanophase-separated morphology observed in the alkylated systems.  Impedance spectroscopy determined hydroxyl-containing imidazolium homopolymers displayed higher ionic conductivities compared to the alkyl-containing analogs which was attributed to increased solvation of electrostatic interactions in the hydroxyl analogs. Beyond functionalizing 1VIM monomers and homopolymers to tailor various properties, the synthesis of novel architectures in a controlled fashion remains difficult due to the radically unstable N-vinyl propagating radical.  The regioisomer 4-vinylimidazole (4VIM) contains two resonance structures affording increased radical stability of the propagating radical.  Nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP) failed to control 4VIM homopolymerizations; however, reversible addition-fragmentation chain transfer (RAFT) demonstrated unprecedented control.  Linear pseudo-first order kinetics were observed and successful chain extension with additional 4VIM suggested preservation of the trithiocarbonate functionality. Effectively controlling the polymerization of 4VIM enabled the design of amphoteric block copolymers for emerging applications.  The design of ABA triblock copolymers with 4VIM as a high T_g supporting outer block and di(ethylene glycol) methyl ether methacrylate (DEGMEMA) as a low T_g, inner block, required the development of a new difunctional RAFT chain transfer agent (CTA).  The difunctional CTA successfully mediated the synthesis of the ABA triblock copolymer, poly(4VIM-b-DEGMEMA-b-4VIM), which exhibited microphase separated morphologies.  The amphoteric nature of the imidazole ring required substantially lower concentrations of outer block incorporation compared to traditional triblock copolymers to achieve similar mechanical properties and microphase separated morphologies. / Ph. D.

High molecular weight polyether urea copolymers were synthesized using perfectly difunctional aromatic amine terminated polypropylene oxide (PPO) (2800 <Mn>) prepared via aluminum porphorin initiated coordination polymerization. The resulting segmented copolymer showed much higher tensile strength and better thermal stability than polyureas based on commercial PPO which contains some terminal unsaturation. This was attributed to the achievement of both higher molecular weight and to more extensive microphase separation between the segments. In addition, the surface structure of segmented polyether urea and polyurethane urea copolymers were modified in two ways: siloxane urea segmented copolymers were synthesized and physically blended into the system, and siloxane oligomers of controlled molecular weight and composition were incorporated into the copolymer backbone as a part of the soft segment. X-ray photoelectron spectroscopy (XPS) was used to obtain surface compositional information, while differential scanning calorimetry (DSC) and stress-strain analysis were used to characterize the bulk properties. In general, the surface enrichment of siloxane was observed in both solvent cast blends and siloxane incorporated systems. The surface siloxane concentration showed a small increase with siloxane segment length, content, and surface sensitive angle. Surface segregation of these systems was suppressed to a certain extent due to phase mixing within the copolymer bulk and by the anchoring of both ends of the siloxane segment with urea components. The bulk properties of these copolymer systems were not affected greatly when small amounts of siloxane ureas were added or when small amounts of siloxane blocks were incorporated. / Master of Science

High performance engineering materials, poly(arylene ether)s, having very good mechanical properties, excellent oxidative and hydrolytic stability are promising candidates for alternative materials used in the field of Proton Exchange Membrane Fuel Cells (PEMFCs) and Reverse Osmosis (RO) applications. In particular, wholly aromatic sulfonated poly(arylene ether sulfone)s are of considerable interest in the field of PEMFCs and RO, due to their affordability, high Tg, and the ease of sulfonation. Proton exchange membrane fuels cells (PEMFCs) are one of the primary alternate source of energy. A Proton exchange membrane (PEM) is one of the key component in a PEMFC and it needs to have good proton conductivity under partially humidified conditions. One of the strategies to increase proton conductivity under partially RH conditions is to synthesize hydrophobic-hydrophilic multiblock copolymers with high Ion exchange capacity (IEC) values to ensure sufficient ion channel size. In this thesis two multiblock systems were synthesized incorporating trisulfonated hydrophilic oligomers and were characterized in the first two chapters of the thesis. The first multiblock system incorporated a non-fluorinated biphenol-based hydrophobic block. The second study was focused on synthesizing a fluorinated benzonitrile-based hydrophobic block. A fluorinated monomer was incorporated with the aim to improve phase separation which might lead to increased performance under partially humidified conditions. The third study featured synthesis and characterization of a novel hydroquinone-based random copolymer system precursor, which after post-sulfonation, shall form mono-sulfonated polysulfone materials with potential applications in reverse osmosis. The ratio of the amount of hydroquinone incorporated in the copolymer were varied during the synthesis of the precursor to facilitate control over the post-sulfonation process. The simple and low cost process of post-sulfonating the random copolymer enables the precursor to be a promising material to be used in the reverse osmosis application. / Master of Science