A series of modified poly(arylene ether sulfone)s (PAES) incorporating hexafluoroisopropylidene units and co-monomers, bisphenol A (BA), 4,4′-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH), were synthesized using a polyetherification synthetic method. These thermoplastic PAES were copolymerized with the elastomer, polydimethylsiloxane (PDMS) to form segmented block copolymers. The segmented block copolymers with diverse PAES structures were studied and investigated for their thermal, tensile, and morphological properties. These multiphase segmented block copolymer materials have the potential to impart useful combinations of optical transparency, thermal stability, and enhanced tensile properties, and enhanced environmentally resistant properties for various high impact, high performance applications. In Chapter 2, hexafluoroisopropylidene bisphenol PAES (BAF PAES) segmented block copolymers containing various volume fraction of PDMS were synthesized. Analysis of the segmented block copolymer films by atomic force microscopy (AFM) and small angle x-ray scattering (SAXS) show the materials are microphase separated. Further analysis of the BAF PAES segmented block copolymers by transmission electron microscopy (TEM) show an increased morphological order with decreasing PDMS content, with lamellar morphologies formed at higher or near equal PAES and PDMS volume fractions. Comparatively, the morphological properties of the BAF PAES segmented block copolymers are considerably different from the isopropylidene bisphenol PAES (BA PAES) segmented block copolymer of similar PDMS volume percents. In this document, segmented block copolymers prepared from BA PAES incorporating 4,4′-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH) co-monomers were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). Films of these materials, prepared from THF solution, were tested for thermal and tensile properties. These materials provide higher thermal stabilities over the BA PAES segmented block copolymers with thermal degradation ranging 380–435 °C under nitrogen at 5%-wt. loss. Similarly, the PAES incorporating co-monomers gave higher Tg (200 °C) than the BA PAES (183 °C) synthesized in our labs. Previously synthesized BA PAES segmented block copolymers showed plastic to elastomeric tensile properties upon increasing addition of PDMS content. These new segmented block copolymers, incorporating co-monomers, provided comparable results with the reported BA PAES segmented block copolymers analogues. The last research topic discussed in this dissertation covers the preparation of blends from 5% of segmented block copolymer and 95% of Udel®, donated by Solvay Advanced Polymers. The preparation of blends from the segmented block copolymers containing random copolymers led to materials with higher moduli than Udel® as observed by dynamic mechanical analysis (DMA). Tensile measurements performed by Instron also show the blends have high moduli, though no changes in the tensile elongation comparable to Udel®. / Ph. D.

The potential success of a proton exchange membrane (PEM) fuel cell as an alternative energy source depends highly upon the development of high performance PEMs. Typically, state-of-the-art PEMs have been perfluorinated sulfonated ionomer membranes such as Nafion® by DuPont. Although these membranes demonstrate good mechanical and electrochemical properties under moderate operating conditions (e.g., < 80 ºC), their performance at high temperature (e.g., > 80 ºC) and low relative humidity (RH) drastically deteriorates. To overcome these problems, PEM materials with enhanced properties are essential. Recently, the McGrath group has shown that PEM materials with hydrophilic-hydrophobic segments can significantly improve proton conductivity under low RH by forming enhanced hydrophilic domain connectivity. In this dissultation, novel multiblock copolymers based on disulfonated hydrophilic-hydrophobic multiblocks were synthesized and investigated for their potential application as PEMs. The relationship between copolymer chemical composition and resulting properties was probed with a variety of hydrophilic and hydrophobic segments. Most multiblock copolymers in this research were developed with fully disulfonated poly(arylene ether sulfone) (BPS100) as the hydrophilic segment, and various high performance polymers including polyimides, poly(arylene ether sulfone)s, and poly(arylene ether ketone)s as the hydrophobic segment. Ionic groups on the hydrophilic blocks act as proton conducting sites, while the non-ionic hydrophobic segments provide mechanical and dimensional stability. The correlation between the fuel cell performances and the hydrophilic-hydrophobic sequences was also evaluated. The morphological structures of the multiblock copolymers were investigated using tapping mode atomic force microscopy (TM-AFM), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The experiments demonstrated a well-defined nanophase separated morphology. Moreover, changes in block length had a pronounced effect on the development of phase separated morphology of the system. Proton conductivity measurements elucidated the transport process in the system, with the multiblock copolymers demonstrating higher conductivities compared to Nafion and random copolymer systems with similar ion exchange capacity (IEC) values. The new materials are strong candidates for use in PEM systems. / Ph. D.

Production of efficiently synthesizable, strongly associating crown ether-based cryptands is desired for pseudorotaxane complexation of bipyridinium guests to produce suprapolymers and supramolecularly-linked block copolymers. Cryptands based on bis(meta-phenylene)-32-crown-10 (BMP32C10) were synthesized. The functionality of phenylenemethanol-BMP32C10 cryptand III-3 (Ka = 2.0 x 104 M-1) did not negatively affect binding strength, although the strength of complexation is marginal to achieve the desired suprapolymers. The cryptand dimethylpyridyl-BMP32C10 IV-2 was synthesized in an attempt to improve over the binding ability of the pyridyl-BMP32C10 cryptand IV-1; instead, interesting host design insights were discovered as binding strengths were reduced over 1000-fold. The crystal structure of IV-2 shows acyl-aryl conjugation which limits the host's ability to accept guests. Synthesis of larger cis-di(carbomethoxybenzo)-3n-crown-n crown ethers was explored using the high concentration, template technique previously reported for cDB24C8 diester. cDB30C10 diester (V-1c) was produced in 93% yield; the desired pyridyl-cDB30C10 cryptand V-12 binds paraquat strongly (Ka = 1-2x105 M-1) and diquat stronger than any other host (Ka = 1.9x106 M-1), both in 1:1 fashions; association constants were measured by ITC. X-ray crystallography of the complexes shows the cryptand's para arm is too far away to interact with paraquat and the host has numerous bifurcated interactions with diquat, explaining the difference in binding strengths. Syntheses of the regioisomers of cDB27C9 diester was also explored; the cyclization yields (cDB27C9S, VI-2: 59% and cDB27C9L, VI-3: 44%) are lower, likely due to poor attack angles due to mismatched arm length in cyclization, than the equivalent length ethyleneoxy-armed cDB24C8 and cDB30C10. Modeling of the cryptand isomers, pyridyl-cDB27C9S and pyridyl-cDB27C9L, showed that the former should improve para arm interaction with paraquat, but should be sterically hindered for diquat and the latter should have a highly flexible, poorly preorganized interaction with either type of guest. ITC, MS, and crystallography data supported the predictions. Derivatization of the pyridyl-cDB30C10 cryptand V-12 was explored using chelidamic acid (VII-1). Schemes yielding alcohol, alkyl halide, alkyne, and TEMPO functionality were followed, but failed. Currently, functionalized cryptand derivatives have not been achieved, future directions are proposed. / Ph. D.

Part I: Single sized, pure arylene ether macrocycles ranging from 30 to 60 atom ring sizes were synthesized in good yields (up to 83%) by the two component method under high dilution conditions. These macrocycles have unsymmetric structures containing sulfone/ketone or sulfone/phosphine oxide functional groups and have relatively low melting points. The melt ROP of the single sized macrocycles to form poly(arylene ether)s exhibits two stage characteristics: the first stage is very fast, driven by the large entropy difference between cyclics and linears; the second stage is very slow and is diffusion controlled due to the high viscosity created in the first stage reaction. The latter stage leads to incomplete polymerization at the low initiator concentrations (1-3 mol%). At high initiator concentrations (5-7 mol%), 100% conversion is reached due to improved initiator distribution in macrocycles; however, this reduces molecular weights of the polymers. The molecular weight is found to build up very rapidly, independent of conversion, reaction time and type of initiator. The ROP is initiated by CsF and alkali phenoxides. The efficiency of the alkali counterion is generally in the order of Cs+>K+>Na+, while a phenoxide initiator is more efficient than a fluoride initiator. It is also found that the Cs counterion leads to highest degree of crosslinking. The ROP of cyclic oligomeric mixtures is also reported for comparison; the study shows that the molecular weight depends on time and conversion, and that the conversion is sensitive to the content of linear impurities and the average ring size of cyclic mixtures. Part II: Polyrotaxanes are novel polymeric materials comprised of linear polymer molecules and threaded macrocycles with no covalent bond between the two components. With potential movements of the cyclic component and judicious combinations of the two components of different properties, these materials have brought interesting changes of physical properties, such as morphology, crystallinity, solubility, viscosity, etc. In this part of the dissertation, a new family of polyrotaxanes with poly(arylene ether)s as backbones and crown ethers as cyclic components are described. These include linear poly(arylene ether) based polyrotaxanes and hyperbranched poly(ether ether ketone) based polyrotaxanes; both are synthesized via aromatic nucleophilic substitution reactions. Preliminary studies show that these polymers exhibit great enhancement of solubility. The polymers form emulsions in water and methanol which are normally non-solvents for the poly(arylene ether) backbones. In some cases, they are even soluble in water to form a clear solution. The attempted syntheses of polyrotaxanes using aromatic macrocycles described in Part I was not successful, with no indication of threading. / Ph. D.

This work is concerned with the production of high performance polymer foams via a benign foaming process. The first goal of this project was to develop a process and the conditions necessary to produce a low density (>80% density reduction) foam from poly(arylene ether sulfone) (PAES). Water and supercritical carbon dioxide (scCO2) were used as the blowing agents in a one-step batch foaming process. Both water and scCO2 plasticize the PAES, allowing for precise control on both the foam morphology and the foam density. To optimize the foaming conditions, both thermogravimetric analysis and differential scanning calorimetery (DSC) were used to determine the solubility and the reduced glass transition temperature (Tg) due to plasticization of the polymer. It was determined that 2 hours was sufficient time to saturate the PAES with water and scCO2 when subjected to a temperature of 220 oC and 10.3 MPa of pressure. Under these conditions, a combination of 7.5% of water and scCO2 were able to diffuse into the PAES specimen, correlating to ~60 oC reduction in the Tg of the PAES. The combination of water and scCO2 produced foam with up to an 80% reduction in density. The compressive properties, tensile modulus, and impact strength of the foam were measured. The relative compressive properties were slightly lower than the commercially available structural foam made of poly(methacrylimide). The second objective of the dissertation was to enhance the compressive properties of the PAES foam, without concern for the foam density. Foam was produced over a range of density, by controlling the cell size, in order to optimize the compressive properties. Carbon nanofibers (CNFs) were also added to the PAES matrix prior to foaming to both induce heterogeneous nucleation, which leads to smaller cell size, and to reinforce the cell walls. Dynamic mechanical thermal analysis (DMTA), on saturated CNF-PAES, was used to determine the reduced Tg due to plasticization and establish the temperature for pressure release during foaming. DMTA proved to be more effective than DSC in establishing quantitative results on the reduction in the Tg. The CNF-PAES foam produced had compressive properties up to 1.5 times the compressive properties of the PAES foam. / Ph. D.

Novel proton exchange membranes (PEMs) were investigated that show potential for operating at higher temperatures in both direct methanol (DMFC) and H2/air PEM fuel cells. The need for thermally stable polymers immediately suggests the possibility of heterocyclic polymers bearing appropriate ion conducting sites. Accordingly, monomers and random disulfonated poly(arylene ether) copolymers containing either naphthalimide, benzoxazole or benzimidazole moieties were synthesized via direct copolymerization. The ion exchange capacity (IEC) was varied by simply changing the ratio of disulfonated monomer to nonsulfonated monomer in the copolymerization step. Water uptake and proton conductivity of cast membranes increased with IEC. The water uptake of these heterocyclic copolymers was lower than that of comparable disulfonated poly(arylene ether) systems, which is a desirable improvement for PEMs. Membrane electrode assemblies were prepared and the initial fuel cell performance of the disulfonated polyimide and polybenzoxazole (PBO) copolymers was very promising at 80 C compared to the state-of-the-art PEM (Nafion®); nevertheless these membranes became brittle under operating conditions. Several series of poly(arylene ether)s based on disodium-3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (S-DCDPS) and a benzimidazole-containing bisphenol were synthesized and afforded copolymers with enhanced stability. Selected properties of these membranes were compared to separately prepared miscible blends of disulfonated poly(arylene ether sulfone) copolymers and polybenzimidazole (PBI). Complexation of the sulfonic acid groups with the PBI structure reduced water swelling and proton conductivity. The enhanced proton conductivity of Nafion® membranes has been proposed to be due to the aggregation of the highly acidic side-chain sulfonic acid sites to form ion channels. A series of side-chain sulfonated poly(arylene ether sulfone) copolymers based on methoxyhydroquinone was synthesized in order to investigate this possible advantage and to couple this with the excellent hydrolytic stability of poly(arylene ether)s. The methoxy groups were deprotected to afford reactive phenolic sites and nucleophilic substitution reactions with functional aryl sulfonates were used to prepare simple aryl or highly acidic fluorinated sulfonated copolymers. The proton conductivity and water sorption of the resulting copolymers increased with the ion exchange capacity, but changing the acidity of the sulfonic acid had no apparent effect. / Ph. D.

A designed series of directly copolymerized homo- and disulfonated copolymers containing controlled degrees of pendant sulfonic acid groups have been synthesized via nucleophilic step polymerization. Novel sulfonated poly (arylene ether sulfone) copolymers using 4,4'-bisphenol A, 4,4'-biphenol, hexafluorinated (6F) bisphenol AF, and hydroquinone, respectively, with dichlorodiphenyl sulfone (DCDPS) and 3,3'-disodiumsulfonyl-4,4'-dichlorodiphenylsulfone (SDCDPS) were investigated. Molar ratios of DCDPS and SDCDPS were systematically varied to produce copolymers of controlled compositions, which contained up to 70 mol% of disulfonic acid moiety. The goal is to identify thermally, hydrolytically, and oxidatively stable high molecular weight, film-forming, ductile ion conducting copolymers, which had properties desirable for proton exchange membranes (PEM) in fuel cells. Commercially available bisphenols were selected to produce cost effective alternative PEMs. Partially aliphatic bisphenol A and hexafluorinated (6F) bisphenol AF produced amorphous copolymers with different thermal oxidative and surface properties. Biphenol and hydroquinone was utilized to produce wholly aromatic copolymers. The sulfonated copolymers were prepared in the sodium-salt form and converted to the acid moiety via two different methodologies and subsequently investigated as proton exchange membranes for fuel cells. Hydrophilicity increased with the level of disulfonation, as expected. Moreover, water sorption increased with increasing mole percent incorporation of SDCDPS. The copolymers' water uptake was a function of both bisphenol structure and degree of disulfonation. Furthermore, the acidification procedures were shown to influence the Tg values, water uptake, and conductivity of the copolymers. Atomic force microscopy (AFM) in the tapping mode confirmed that the morphology of the copolymers could be designed to display nanophase separation in the hydrophobic and hydrophilic (sulfonated) regions. Morphology with either co-continuous hydrophobic or hydrophilic domains could be attained for all the sulfonated copolymers. The degree of disulfonation required for continuity of the hydrophilic phase varied with biphenol structure. Proton conductivity values for the sulfonated copolymers, under fully hydrated conditions, were a function of bisphenol and degree of sulfonation. However, at equivalent ion exchange capacities the proton conductivities were comparable. A careful balance of copolymer composition and acidification method was necessary to afford a morphology that produced ductile films, which were also sufficiently proton conductive. The copolymers of optimum design produced values of 0.1 S/cm or higher, which were comparable to the commercial polyperfluorosulfonic acid material Nafion™ control. / Ph. D.

Novel proton exchange (PEM) and reverse osmosis (RO) membranes for application in fuel cell and water purification respectively were developed by synthesis and crosslinking of disulfonated biphenol-based poly (arylene ether sulfone)s (BPS). Crosslinking is a prospective option to reduce the water swelling and improve the dimensional stability of hydrophilic BPS copolymers. Several series of controlled molecular weight, phenoxide-endcapped BPS copolymers were synthesized via direct copolymerization of disulfonated activated aromatic halide monomers. The degree of disulfonation was controlled by varying the molar ratio of sulfonated to non-sulfonated dihalide monomers. The molecular weights of the copolymers were controlled by offsetting the stoichiometry between biphenol and the dihalides. Biphenol was utilized in excess to endcap the copolymers with phenoxide groups, so that the phenoxide groups could be further reacted with a suitable crosslinker. Several crosslinking reagents such as methacrylate, multifunctional epoxy, phthalonitrile and phenylethynyls were investigated. A wide range of crosslinking chemistries i.e. free radical (methacrylate), step growth (epoxy), heterocyclic (phthalonitrile) and acetylenic (phenylethynyl) was explored. The effects of crosslinking on network properties as functions of molecular weight and degree of disulfonation of copolymers, crosslinking time and concentration of crosslinker were studied. The crosslinked membranes were characterized in terms of gel fraction, water uptake, swelling, self-diffusion coefficients of water, proton conductivity, methanol permeability, water permeability and salt rejection. In general, all of the crosslinked membranes had lower water uptake and swelling relative to their uncrosslinked counterparts, and less water uptake and volume swelling were correlated with increasing gel fractions. It was possible to shift the percolation threshold for water absorption of BPS copolymers to a higher ion exchange capacity (IEC) value compared to that of the uncrosslinked copolymers by means of crosslinking. This reduced water uptake increased the dimensional stability of higher IEC materials and extended their application for potential PEM or RO membranes. The reduction in water uptake and swelling also increased the effective proton concentration, resulting in no significant change in proton conductivity of the membranes after crosslinking. The self-diffusion coefficients of water and methanol permeability decreased with crosslinking, indicating restricted water and methanol transport. Therefore an improvement in the selectivity (ratio of proton conductivity to water swelling or methanol permeability) of PEMs for application in either H2/air or direct methanol fuel cells was achieved by crosslinking. The epoxy crosslinked BPS copolymers also had significantly enhanced salt rejection with high water permeability when tested in for RO applications. Reductions in salt permeability with increasing crosslinking density suggested that crosslinking inhibited salt transport through the membrane. In addition to the random copolymers, two series of multiblocks endcapped with either a phenoxide-terminated hydrophilic unit or a hydrophobic unit were synthesized and crosslinked with a multifunctional epoxy. Besides the crosslinking study, the effect of sequence distributions of the hydrophilic and hydrophobic blocks in the multiblock copolymers was also investigated. Similar to randoms, crosslinked multiblocks had lower water uptake and swelling but comparable proton conductivities relative to their uncrosslinked analogues. / Ph. D.

Novel, highly functional rod-like copolymers have been synthesized by alternating copolymerization of N, N, Nâ , Nâ -tetraalkyl-4, 4â -diaminostilbenes (TDAS) with maleic anhydride. Dynamic light scattering, 2H solid state NMR and persistence length measurement reveal high chain rigidity of the polymer backbone. Double quantum heteronuclear local field solid state NMR spectroscopy (2Q-HLF Solid State NMR) has been employed to investigate the chain structure of ¹³C labelled copolymer. The torsional angle of the H-13C-13C-H part of the anhydride ring was zero degrees, indicating an all cis configuration of the H-13C-13C-H moiety of the anhydride ring. Rod-coil block copolymers containing rigid polyampholyte blocks were designed and synthesized by addition-fragmentation chain transfer (RAFT) copolymerization. The rigid polyampholytes blocks were formed by hydrolysis of alternating copolymers and the flexible coil block consists of poly(oligo(ethylene glycol) methacrylate). The rod-coil block copolymers form polyion complex (PIC) aggregates even when the polyampholyte blocks are charge imbalanced. The aggregates did not dissociate upon the addition of high concentrations of NaCl unlike the dissociation of flexible polyampholytes in NaCl solution. These unique solution properties are induced by 'like-charge attractions' of the rigid polyampholytic alternating copolymer chains. An example, of what is birefringent to be a novel class of material, has been prepared which enables the control of the birefringence of a polymer film by controlling the rotation of aromatic groups pendant to the polymer backbone. A linear rigid bisphenol monomer, 4,4′-dihydroxyterphenyl (DHTP), has been incorporated into poly(aryl ether sulfone)s (PAES) in a study to impart crystallization to these amorphous polymers. Three bisphenols, 4, 4′-isopropylidenediphenol, 4, 4′-(hexafluoroisopropylidene)diphenol and 4,4′-dihydroxybiphenyl have been copolymerized with DHTP and dichlorodiphenylsulfone. Only the segmented polysulfone containing 50% BP and 50% DHTP was semi-crystalline. This PAES had a melting temperature (Tm) 320°C in the first heating cycle of a DSC measurement and the presence of crystallites was confirmed by wide angle X-ray diffraction (WAXS). / Ph. D.

Two novel classes of siloxane containing, organic-inorganic block copolymers were prepared using different synthetic approaches. The first copolymers were alternating poly(arylene ether phosphine oxide)-poly(dimethylsiloxane) systems, prepared via oligomeric silylamine-hydroxyl reactions. Secondly, segmented nylon 6,6-poly(dimethylsiloxane) block copolymers were synthesized via a non-aqueous adaptation of the "nylon 6,6 salt" hydrolytic polyamidization, using bis(aminopropyl) dimethylsiloxane oligomer as a co-reactant. Three series of "perfectly" alternating block copolymers were produced from well characterized hydroxyl-terminated poly(arylene ether phosphine oxide) and dimethylamine-terminated poly(dimethylsiloxane) oligomers, in order to investigate both block length and chemical composition effects. Copolymerization in chlorobenzene resulted in high molecular weight materials capable of forming optically clear, nanophase separated films, which displayed unusual morphologies and good mechanical strength. Thermal gravimetric analysis showed high thermo-oxidative stability and increasing char yield with increasing siloxane content. Additional thermal and mechanical investigations provided evidence of selective phase mixing, particularly at shorter block lengths. Surface analysis showed an enrichment of the siloxane blocks at the air-polymer interface in comparison to the bulk state. This behavior increased in proportion to the length of the parent siloxane oligomers. Evaluation of selected optical properties, e.g., refractive indices, revealed linear trends resulting in values of compositionally weighted averages. Conversely, a series of nylon 6,6-siloxane copolymers were produced from the polycondensation of preformed propylamine-terminated poly(dimethylsiloxane)s, solid nylon 6,6 salt and a corresponding amount of adipic acid to afford siloxane-amide semi-crystalline copolymers with siloxane content ranging from 10 to ~45 wt%. The characterization of high molecular weight and covalent siloxane-amide linkages was hindered by insolubility. For example, crystallinity of the nylon 6,6 precluded the use of common solution techniques, while the susceptibility of the siloxane blocks towards ionic redistribution prevented the use of strongly acidic solvents. However, development of a novel analytical technique using solid state 13C NMR and liquid-solid extraction provided evidence for the presence of covalent bonding between the dissimilar oligomer chains. Thermal gravimetric analysis of resultant copolymers revealed an increase in char yield with increasing siloxane content, a preliminary indicator of increased fire resistance, which was supported by subsequent qualitative Bunsen burner observations. Differential scanning calorimetry showed retention of the polyamide crystalline melt with levels of siloxane incorporation of up to 45 weight %. In conclusion, two novel classes of polydimethylsiloxane containing block copolymers have been successfully synthesized, despite the complications created as a result of the polar/non-polar interactions developed between a semi-inorganic polydimethylsiloxane and the hydrocarbon based polyarylene ethers and nylon 6,6. / Ph. D.