Polyaromatic hydrocarbons (PAH) are useful molecules for supramolecular assemblies and nanoscale electronics materials. Due to their high degree of symmetry and lack of heteroatoms characterization is fairly simple and calculated properties very closely match experimental values. By utilizing a controlled, stepwise synthesis, which enables the regioselective incorporation of solubilizing side chains and electron donating or withdrawing groups, we were able to access many novel PAHs of various shapes and sizes. Using an unprecedented asymmetric protected alcohol-benzyl bromide Collman coupling strategy we have accessed linear oligocyclopentadienones and oligophenylenes not accessible through current methodology. Monomers of these two classes were studied both spectroscopically and computationally in order to fully characterize their electronic structure and see how perturbation of the PAH scaffold affected their respective molecular orbitals. Using a harsher unsymmetrical carbonylative coupling of α,α'-dibromoxylene we were able to access the two previously unknown low molecular weight polymers: Poly(para-phenylene)(2-isocyano-2-tosylpropane-1,3-diyl) (PPIT), and Poly(paraphenylene)( 2-oxopropane-1,3-diyl) (PPOD). PPIT and PPOD were demonstrated to be possible precursors of high molecular weight polycyclopentadienones and polyphenylenes. Small macrocycles of these polymers were also produced through the same methodology at high dilution. Conversion of the polymers and oligomers to linear and cyclic polycyclopentadienones and polyphenylenes has been demonstrated in two prototypic examples. While universal methodology for larger oligomers and polymers is still under study, we believe the ultimate goal of discrete isomer carbon nanotubes and linear graphite to be possible due in part by the work reported in this thesis.

Diels-Alder polyphenylenes (DAPPs) are chemically and thermally stable polymers, used for dielectric resins, gas separation membranes, and fuel cell proton exchange membranes. Highly fluorinated DAPPs are expected to have better thermal stability and chemical resistance, higher glass transition temperatures, improved compatibility with other fluorinated polymers (like NafionTM), and better adhesion to certain surfaces such as some metals. This thesis proposes a synthesis of highly fluorinated DAPPs by reacting novel, fluorinated bis-cyclopentadienone (CPD) monomers with known aromatic dialkynes. This thesis starts with an introduction to DAPP synthesis, properties, and applications. The second chapter focuses on the synthesis of 4,4′-bis[1,2,4-tris(perfluoro-4-tolyl)cyclopentadien-5-one-3-yl]octafluorobiphenyl (CPD monomer). In the first step, disodiumbis(cyclopentadieny)octafluorobiphenyl was combined with 6 equivalents of octafluorotoluene in HMPA to give 4,4′-bis[1,2,4-tris(perfluoro-4-tolyl)cyclopentadiene-3-yl]octafluorobiphenyl. Oxidation to the corresponding diketone was effected using selenium dioxide. The synthesis of CPD monomer presented several unexpected challenges that were ultimately overcome. The third chapter describes a series of initial polymerization experiments as well as some model reactions that were carried out to understand monomer reactivity. Finally the future research plan of synthesizing different polymers by Diels-Alder reaction and nucleophilic substitution reaction has been discussed. / Master of Science

The first chapter of this dissertation reports the synthesis of highly fluorinated Diels-Alder polyphenylenes. The first section of this chapter describes the three-pot synthesis of a perfluoroarylated bis(cyclopentadienone) monomer. The synthesis begins with the previously reported substitution reaction of decafluorobiphenyl and sodium cyclopentadienide. To the resulting 4,4'-octafluorobiphenylene-linked bis(cyclopentadiene), six perfluoro-4-tolyl groups (three on each of the two cyclopentadienyl moieties) are attached by nucleophilic aromatic substitution (SNAr) reactions. The remaining ring methylenes are subjected to a selenium dioxide-catalyzed oxidation to obtain the desired bis(cyclopentadienone) monomer. The next part of this chapter describes the polymerization of the perfluoroarylated bis-(cyclopentadienone) monomer and bis(4-ethynylphenyl) ether. The reaction affords an oligomer (Mn ~ 14,000 g/mol according to size-exclusion chromatographic analysis) that is soluble in several solvents and that decomposes above about 300°C according to thermogravimetric analysis. The second chapter of this dissertation describes a novel method to oxidize per-fluoroarylated cyclopentadiene compounds to the corresponding ketones using catalytic selenium dioxide and stoichiometric hydrogen peroxide. The first part of this chapter shows the synthesis of some perfluoroarylated cyclopentadiene substrates, while the second part of the chapter explores the oxidation of these compounds along with other perfluoroarylated cyclopentadienes already available within our research group. This chapter also explains how the reactivity of the perfluoroarylated cyclopentadienes under the oxidation conditions depends on their structure. Generally more electron-deficient cyclopentadienes react more readily, while sterically crowded cyclopentadienes react more reluctantly. This third chapter of this dissertation describes the synthesis and characterization of a reversible Diels-Alder polymer from an octafluorobiphenylene-linked bis(cyclopentadiene). In the first section, the synthesis of a reversible homopolymer of the bis(cyclopentadiene) monomer is described. The polymer reaches an optimized molecular weight of 11,000 g/mol (degree of polymerization is 20) under the reaction conditions because there is an equilibrium between polymerization and depolymerization even at the mild polymerization temperature (65°C). The TGA trace of the polymer shows that chain degradation takes place beyond 300°C. The thermal reversibility of the polymer was examined by bulk thermolysis, and flash-vacuum thermolysis. The second section describes the synthesis of a methylated bis(cyclopentadiene) that does not undergo self-polymerization at comparatively lower temperature but instead reacts with a second bis(maleimide) monomer. The resulting polymer typically shows a number-average molecular weight of 15,400 g/mol. This polymerization also is limited by the attainment of steady-state end group concentrations. The reversibility of the polymerization is demonstrated by solution thermolysis experiments in which unmasked cyclopentadiene groups are trapped by a monofunctional maleimide. / Ph. D.

No description available.

Neue nanoporöse Materialien mit niedrigen Dielektrizitätskonstanten werden in der Mikroelektronik dringend benötigt. Eine Methode, die Dielektrizitätskonstante eines gegebenen Materials weiter zu reduzieren, ist die Einführung von geschlossenen und luftgefüllten Poren im Nanometerbereich. Die Porosität wird durch die Verwendung eines Zweikomponentensystems bestehend aus einer stabilen Matrix und einem labilen Porenbildner eingeführt; aus diesen wird ein Blend hergestellt, und durch anschließende Zersetzung des Porenbildners entsteht ein poröses Matrixpolymer mit stabilen Aushöhlungen. Im Vordergrund dieser Arbeit stand die Synthese und Charakterisierung hochverzweigter Polyphenylene über die Diels-Alder-Reaktion von phenylierten Cyclopentadienonen mit phenylierten Alkinen zur Verwendung als Matrixmaterialien in nanoporösen Isolatorsystemen. Dabei wurde sowohl von A2- und B3-Monomeren als auch von AB2- und AB-Monomeren ausgegangen. Die hochverzweigten Polyphenylene sind vielversprechende Materialien mit hervorragenden isolierenden und chemischen Eigenschaften wie hohen thermischen Stabilitäten und guten Löslichkeiten in organischen Lösungsmitteln, was eine wichtige Voraussetzung für die Verwendung der Polymere in der Mikroelektronik darstellt. Die verschiedenen Syntheseansätze erlauben dabei eine Kontrolle über die Endgruppen und die Verzweigung. Daneben wurden thermolabile hochverzweigte Polycarbonate und Polytriazenester als Porenbildner synthetisiert und mit Silylether-Endgruppen modifiziert, wobei mit der tert-Butyldiphenylsilyl-Gruppe die besten Ergebnisse bezüglich der Mischbarkeit mit der Polyphenylenmatrix erhalten wurden. Außerdem wurden Blends in Form von dünnen Schichten aus den hochverzweigten Polyphenylenen mit den Porenbildnern im Hinblick auf die potentielle Anwendung der Materialien als nanoporöse Isolatoren charakterisiert.

Neue nanoporöse Materialien mit niedrigen Dielektrizitätskonstanten werden in der Mikroelektronik dringend benötigt. Eine Methode, die Dielektrizitätskonstante eines gegebenen Materials weiter zu reduzieren, ist die Einführung von geschlossenen und luftgefüllten Poren im Nanometerbereich. Die Porosität wird durch die Verwendung eines Zweikomponentensystems bestehend aus einer stabilen Matrix und einem labilen Porenbildner eingeführt; aus diesen wird ein Blend hergestellt, und durch anschließende Zersetzung des Porenbildners entsteht ein poröses Matrixpolymer mit stabilen Aushöhlungen. Im Vordergrund dieser Arbeit stand die Synthese und Charakterisierung hochverzweigter Polyphenylene über die Diels-Alder-Reaktion von phenylierten Cyclopentadienonen mit phenylierten Alkinen zur Verwendung als Matrixmaterialien in nanoporösen Isolatorsystemen. Dabei wurde sowohl von A2- und B3-Monomeren als auch von AB2- und AB-Monomeren ausgegangen. Die hochverzweigten Polyphenylene sind vielversprechende Materialien mit hervorragenden isolierenden und chemischen Eigenschaften wie hohen thermischen Stabilitäten und guten Löslichkeiten in organischen Lösungsmitteln, was eine wichtige Voraussetzung für die Verwendung der Polymere in der Mikroelektronik darstellt. Die verschiedenen Syntheseansätze erlauben dabei eine Kontrolle über die Endgruppen und die Verzweigung. Daneben wurden thermolabile hochverzweigte Polycarbonate und Polytriazenester als Porenbildner synthetisiert und mit Silylether-Endgruppen modifiziert, wobei mit der tert-Butyldiphenylsilyl-Gruppe die besten Ergebnisse bezüglich der Mischbarkeit mit der Polyphenylenmatrix erhalten wurden. Außerdem wurden Blends in Form von dünnen Schichten aus den hochverzweigten Polyphenylenen mit den Porenbildnern im Hinblick auf die potentielle Anwendung der Materialien als nanoporöse Isolatoren charakterisiert.

Proton conducting membranes are a key component in fuel cell designs. Properties like proton conductivity, water uptake, ion exchange capacity and physiochemical stability dictate the performance and longevity of the complete fuel cell system. Designing a proton conductiting membrane takes several factors, such as monomer choice and their respective functionalization into account. Besides that, economically favourable reactions as well as environmental compability have to be considered. This work demonstrates the development of a fuel cell membrane material starting from broadly available, cost-efficient educts. Few reaction steps, also including cost-efficient reagents, have been employed in order to obtain a doubly sulfonated monomer based on naphthalene-1,5-disulfonic acid (Armstrong´s acid) suitable for polymerizations. Suzuki polycondensation of the given monomer partly yielded processable films for further investigation. A cost-efficient, atom-economic deprotection stategy was developed for sulfonated polyphenylenes, yielding proton conducting membranes. Further modification of the backbone structure, by incorporating an excess of hydrophobic meta,meta,meta-terphenylene units, led towards balanced properties of the material. The impact of polymer constitution, was investigated and discussed via the implementation of para,meta,para-substituted instead of meta,meta,meta-substituted terphenylene. Alternating and statistical copolymers including para,meta,para-substituted terphenylene were developed and investigated. The reported proton conducting membranes pose suitable and promising candidates for fuel cell applications.