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.

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

The polyamide poly(ε-caprolactam) or "nylon 6" is a very important fiber forming polymer which finds many applications in the carpet industry and elsewhere due to the very high strength of this fiber. However, a major drawback is its hydrophilicity. This feature influences both the surface and bulk mechanical behavior. Siloxane based macromolecules are hydrophobic, thermally stable and exhibit dimensional stability over a wide temperature range. Unlike the polyamide nylon 6, these hydrophobic materials display relatively low surface free energy. Thus, they can be used for the surface modification of nylon 6, provided a suitable adhesion or "anchoring" method is feasible. Polyamide-polydimethylsiloxane segmented or block copolymers were found to be suitable "interfacial" agents. They were synthesized by reacting aminopropyl-terminated polydimethylsiloxane (PDMS) oligomers with sebacyl chloride via an interfacial polymerization in which methylene chloride was used as the solvent or organic phase. A second diamine "chain extender" was also utilized, if desired. By varying the mole ratio of soft segment to the chain extender p-aminocyclohexylmethane (PACM-20), copolymers with various percentages of hard segments can be synthesized. Weight fractions of 2, 5, or 10% of the polyamide-poly-dimethylsiloxane block copolymers were physically melt mixed with nylon 6 in an extruder. The presence of polydimethylsiloxane on the surface of the blend was detected by determining the critical surface tensions of wetting using water as the contact angle test liquid. Such modified polyamides were successfully melt spun into fibers which displayed good mechanical properties and enhanced soil resistance. Fibers spun from these modified nylon 6 blends showed surface hydrophobicity. These modified polyamides or related materials may become technologically important in carpeting applications. Additional studies involving attempts at directly polymerizing ε-caprolactam via hydrolytic ring opening polymerization from functional polysiloxanes are also reported. In general, the structural integrity of these copolymers is less well defined. Certain procedures utilizing the aminopropyl polydimethylsiloxane initiated lactam oligomerization, followed by adipic acid chain extension produced interesting materials and should be further examined. / Master of Science / incomplete_metadata

Novel perfectly alternating segmented copolymers containing imide junction points were synthesized via terminal amine-anhydride coupling from poly(dimethylsiloxane)s and either poly(arylene ether)s or polyimides. The copolymers were characterized in solution and the solid state. The -(-A-B-)-n architecture and molecular design of these linear systems afforded thermodynamically microphase separated systems which gave rise to interesting copolymer properties. Each controlled molecular weight oligomeric segment, or homopolymer, was initally synthesized with reactive endgroups and fully characterized prior to copolymerization. Thus, anhydride-terminated poly(dimethylsiloxane)s were prepared via cationic ring-opening polymerization in the presence of a "monofunctional" bis-norbornane anhydride disiloxane endcapping species. Aromatic amine-terminated engineering thermoplastics were synthesized through either nucleophilic aromatic substitution in the presence of a “monofunctional” aminophenol endcapper (as for poly(arylene ether ketone)s and poly(arylene ether sulfone)) or by solution imidization using a controlled excess of the diamine monomer. A solution imidization method was developed for the segmented copolymerization that simplified the typically two-step, two-solvent method into a one-step approach with a single solvent. Thus, a previously described condensation catalyst, 2-hydroxypyridine, was utilized which was demonstrated to be essential in obtaining high molecular weight copolymers. These segmented copolymers generally were fibrous and highly soluble in many common organic solvents. Creasable, transparent, solution-cast films were readily prepared. Thermal and morphological analyses demonstrated that the copolymers exhibited phase separation, and displayed lower and upper Tg's as a result of the two components employed. At short hard block lengths, uper Tg's were somewhat depressed, implying partial miscibility. / Master of Science

This work combines many characterization techniques in an effort to enhance understanding of molecular motions of polymers and. how they are influenced by' structure. The primary characterization method was dielectric spectroscopy which utilizes an AC electric field as the stress field. A variety of new, well controlled polymeric systems were studied. The first series included a number of radial starblock copolymers, styrene/isoprene, t-butyl- styrene/isoprene, and t-butyl-styrene/butadiene. These ABA copolymers consisted of hard and soft blocks, with the soft block comprising 75% by weight. The effect of microstructure of the soft block, casting solvent, hydrogenation, and chemical composition of the hard block were some of the variables studied. The amount of phase separation and the molecular motions occurring will be influenced by these parameters. Hydrogenation of the soft block increased the phase separation. Another system investigated included some stereospecific poly(alkyl methacrylates) which were synthesized anionically. In this series the alkyl group was systematically changed in order to study the effects of the bulkiness of the substituent and the tacticity on the a and ß transitions. The ß transition associated with side chain rotations was only observed in the case of the methyl and ethyl substituents. The Havriliak-Negami data analysis was used to evaluate the breadth and the skewness of the distribution of relaxation times. Finally, some high temperature thermoplastic polymers were evaluated with dielectric spectroscopy. The effect of the backbone composition, moisture, and fillers on the β transition was looked at. These studies showed that moisture and fillers play an important role on the magnitude and temperature of the observed β transition. / Ph. D.

Three block copolymer systems where one block was that of an engineering thermoplastic were examined. The first was that of polysulfone-polyarylester block copolymers where glassy-crystalline block copolymers were synthesized and characterized. The morphology of the block copolymers could be controlled by varying the chemical microstructure of the polyester segment. Solvent resistance was shown to improve as the level of crystallinity was increased. Segmented block copolymers of an amorphous polyarylester and polydimethylsiloxane were also investigated. Both the random-block and perfectly alternating synthetic routes were used and it was found that the perfectly alternating technique produced a more regular morphology; than the random-block technique. A study was also carried out on the incorporation of small amounts of polysulfone-polydimethylsiloxane block copolymers blended into homopolysulfone. Improved fracture toughness was observed without a significant loss of stiffness. The morphology of block copolymer particles dispersed in the polysulfone matrix was directly observed through transmission electron microscopy. / Ph. D.

Over the years there have been many studies on the theoretical and phenomenalogical aspects of starblock, di- and tri-block copolymer systems with very narrow molecular weight distributions. However, in many real multiblock systems the effect of such variables as; chemical composition distribution, molecular weight distribution and block architecture, among others, are not very well understood. The key to gaining a better understanding of these systems lies in the use of synthetic and process controlled variables. Seven different systems were used to study the effect of various synthetic and process controlled variables. The poly(butene sulfone) (PBS)-polydimethylsiloxane (PDMS) graft copolymers were synthesized by a free radical technique which involves the terpolymerization of butene, SO, and hexenyl functionalized polydimethylsiloxane macromonomers. The surface and bulk morphologies of a series of PBS-g-PDMS compolymers with 1, 5, 10, and 20K PDMS graft molecular weights at 5 and 20Wt.% PDMS incorporation. Additionally, for each graft molecular weight and at each composition, copolymers with a low and a high degree of polymerization of the PBS backbone were analyzed. A two phase morphology was found to exist with PDMS domain size increasing with increasing PDMS graft length. The type of morphology observed was dependent on PDMS composition, and in some cases the degree of polymerization and average number of grafts/backbone. These factors were also found alter the nature of the surface morphology and the related surface properties. The effect of PDMS segment molecular weight, the chemical nature of the polyimide segment, the procedure used to imidized the polyimide and processing conditions on the structure-property relationships in a series of polyimide-PDMS containing approximately 15Wt.% PDMS was studied. It was determined that as the polarity of the polyimide segment increased the morphology shifted to texture with lower surface/volume ratios. Casting the copolymers from an NMP solution favored a more discrete morphology than the thermally treated compression molded samples. The modulus was found to increase as the degree of phase separation increased with increasing PDMS segment size at constant composition. In addition, the solution cast films were found to have a higher modulus than the compression molded analogs. The morphology of a series of methacrylate based block ionomer was investigated. The effect of ionic block length, the architecture of the segments, and variations in the nature of ionic group were studied. SAXS revealed the presence of multiple scattering maxima in the dilbock materials. Both highly ordered and disordered region were observed from TEM analysis. The observed spacing from TEM measurements and SAXS were in good agreement. The interdomain spacings between the ionic domains were found to be a strong function of ionic block length. / Ph. D.

During the past few years, studies involving the synthesis, characterization, and structure-property relations of especially well-defined or "model" block and graft copolymers have received increasing interest among academic and industrial communities. The well-defined nature of such polymers makes them ideal subjects for both fundamental studies and specialty polymer applications. This study addresses the synthesis and characterization of well-defined block and graft copolymers through the use of reactor systems and permeability instrumentation designed specifically for this purpose. The engineering design, construction, operation, and in some cases automation of the above instrumentation is discussed in detail. Examples of the synthesis and permeability characterization of several especially interesting multiphase graft and star block copolymers are provided to demonstrate the utility of the instrumentation described. The primary focus of this work has been to address the effects of varying degrees of microphase separation and morphological development on the physical properties of well-defined block and graft copolymers and their hydrogenated derivatives. The application of gas permeability as an especially sensitive probe of morphology in well-defined poly(methylmethacrylate) -poly(dimethylsiloxane) graft copolymers has been given special emphasis. The synthesis these graft copolymers has been accomplished by the copolymerization of model, methacrylate-functional, poly(dimethylsiloxane) CPDMS) "macromonomers" with methylmethacrylate, using conventional free-radical and novel anionic and group transfer techniques. These techniques are described and referenced with chemical characterization provided. The resulting graft copolymers have PDMS-modified surface and bulk morphologies that dominate particular physical property responses and provide for interesting structure-permeability studies. The characterization of these copolymers to demonstrate their well-defined nature has been performed with a focus on the application of gas permeability as an especially sensitive morphological probe. A review of the relevant literature is followed by detailed experimental procedures, a summary and discussion of results, and descriptive appendices. The appendices include details concerning the design, fabrication, and automation of instrumentation to perform volumetric, equilibrium sorption experiments and computer programs for the acquisition and analysis of permeability data. / Ph. D.