The synthesis and physical characterization of various poly(1,4-phenylene vinylene) (PPVs) derivatives with electron withdrawing substituents on the phenyl rings and some additional PPV analogues are described. The synthetic routes used were a variation on the Wessling route to PPV which involves a processible precursor polymer. All polymers were characterized by IR, UV and elemental analysis. The effect of substitution on the phenyl ring and solvent effects on polymerization were also discussed. Para-xylylenes were generated by treatment of various 1,4-bis(dialkylsulfoniomethyl) arene dihalides in different solvents and detected by UV-VIS spectroscopy. The utility of studying the UV-VIS spectral behavior of para-xylylenes and analogues in the Wessling polyelectrolyte precursor process for synthesis of poly(arylene vinylene)s is demonstrated by several examples. Electronic spectral properties such as UV-VIS absorption and photoluminescence spectroscopy of PPV derivatives and analogues were investigated.

Aqueous reaction of $\alpha$,$\alpha\prime$-bis(dialkylsulfonium)-p-xylenes with base to obtain polyelectrolytes has been known since 1968, when two groups showed thermal annealing of the polymer would yield poly(p-phenylene vinylene) (PPV). Many recent papers have discussed conductive and optical properties of PPV made by this route, but until now, no comprehensive study of the polymerization events has been reported. In the previously accepted mechanism, reaction proceeds by (1) formation of ylides, (2) 1,6-elimination to the quinodimethanes (QDs), (3) generation of diradical initiatiors by tail-to-tail dimerization of QDs, and (4) radical chain propagation. No sulfonium-substituted olefins besides these QDs are known to homopolymerize. This dissertation reviews several areas: organic solid-state properties; history of PPV syntheses; science and technology of the precursor route to PPV; and chemistry of sulfonium compounds, QDs, and related species. UV-vis and NMR spectroscopy experiments gave the strongest evidence to date for the intermediacy of reversibly formed transient ylides and QDs. No equilibrium between QDs and products was detected in the presence of radical traps. Substituent effects on QD stability were pronounced. Exogenous pi-compounds exhibited concentration-dependent effects on QD consumption rates; formation of diradical adducts with the QDs is postulated. Faint UV irradiation caused two effects: accelerated formation of QDs, and acceleration of their reaction rates. Novel methods for converting the polyelectrolyte into analytes suitable for gel permeation chromatography were developed. These involved nucleophilic substitution by mono- or dibasic salts for they utilized counterion exchange; several of the new materials had not been previously described. Characterization of thiophenylated derivatives found large, highly polydisperse molecular weights. The decrease in chain size obtained when radical probes were present during polymerization was consistent with radical propagation. Electron spin resonance studies suggest that diminutive, spontaneously-formed radical populations develop during polymerization. Single electron transfer and nonradical reactions were disproved. Gas chromatograph/mass spectrometry analysis of products from dilute reactions suggest head-to-tail dimerization of QDs occurs; (2.2) paracyclophanes (cyclic dimers) could not be found.

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This dissertation reports a simple route to synthesis nanostructured composites by immobilizing colloidal crystals (CCs) of monodisperse SiO2 spheres in crosslinked polymer network. The resulting ordered nanocomposites exhibited the highest modulus reported yet, to the best of our knowledge, for similar materials. The ordered nanocomposites were optically active and the Bragg diffracted light in a NIR region and wavelength of the Bragg peak could be tuned simply by changing the silica concentration in the composite. They also exhibited intense angle dependent iridescence. / Chemistry

A number of nitroxide adducts and N-acyloxytrialkylammonium salts were prepared, isolated, characterized and evaluated as initiators for the controlled and living free radical polymerization of methacrylate and dimethacrylate monomers under mildly thermal and photochemical conditions. The initiators and polymerization methods that were developed could potentially be used for improving resins employed in dental applications. Using very easy synthesis strategies, the following nitroxide initiators were prepared in high purity, isolated and characterized: 1-Benzoylperoxy-2,2,6,6-tetramethyl-piperidine (BPO/TEMPO), 1-(2'-Cyano-2'-propoxy)-2,2,6,6-tetramethylpiperidine (AIBN/TEMPO), 1,1-ditertbutyl-1-(1-methyl-1-cyanoethoxy)-amine (AIBN/DBN), 1,1-ditertbutyl-1-(benzoylperoxy)-amine (BPO/DBN) and 2,2,6,6,-tetramethyl-4-oxo-1-(1-methyl-1-cyanoethoxy)-piperidine (AIBN/4-OXO-TEMPO). Using H2SO4 additive and an improved unimolecular initiation in nitroxide mediated polymerization, living and controlled polymerization of methyl methacrylate (MMA), tri-ethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA) were accomplished, for the first time ever for most of the initiators. Linear polymers (PMMA) were produced in high yield (93 %) under mildly thermal conditions (T = 70 oC) and with excellent attributes: (PDI = 1.04-1.26), Mn (87000), Tg (122-128 oC), Td (290-410 oC). Highly crosslinked polymers, poly(TEGDMA) and poly(EBPADMA), were produced in high yield (100 %) with Td (350-400 oC). The initiators were stable for a year and half at 0 oC. Two routes were investigated for the preparation of N-acyloxytrialkylammonium salts. The more efficient of these routes was used to make several novel analogs of the salts. The salts were evaluated for the free radical polymerization of MMA, TEGDMA and EBPADMA under mildly thermal (T = 60 oC) conditions with and without H2SO4 additive. Polymerization rate, yield and polymer attributes all improved upon application of H2SO4 additive. PMMA was produced with excellent attributes (PDI = 1.01-1.06), Mn (96,000-122000), Td (330-385) and Tg (127-134). Highly crosslinked poly(TEGDMA) and poly(EBPADMA) were produced with Td ranges of 300-374 oC and 375-411 oC respectively. / Chemistry

Model compound were synthesized and their photochemical behavior studied to better understand polymer systems. Synthesis of poly(4$\sp\prime$vinyl-2,4,6-tri-tert-butyl-diphenyloxalate), its 65: 35 and 19: 81 copolymers with styrene, and poly (3,5-di-tert-butyl-4- ((2,4,6-tri-tert-butyl-phenyl)oxalato) -phenylacetylene) are described. Rigid phase broad-band photolysis of both saturated and unsaturated polymers with a quartz filtered xenon arc at 77 K resulted in production of up to 25% of the theoretical number of spins/mol expected for quantitative production of pendant phenoxyl radicals, and showed no major loss of radical signal in the ESR at temperatures below 100 K. Curie law analyses of the temperature dependence of the ESR radical signal intensity for neat photolyzed samples of saturated homopolymer 78 and unsaturated polymer 92 show curvature consistent with antiferromagnetic pairing of radicals spins and nearly paramagnetic behavior, respectively, at low temperatures. Since through-bond conjugation of radical spins is not possible in 78, the antiferromagnetic interaction is interpreted in terms of intrachain and/or interchain through-space exchange interactions. We tentatively ascribe the nearly paramagnetic behavior observed for 92, instead of the expected antiferromagnetic interaction, to conformational and/or morphological factors.

This thesis describes the preliminary work conducted in the design and synthesis of polymeric materials that exhibit temperature dependent molecular weights. ABA (hard-soft-hard) tri-block oligomers were synthesized possessing hydrogen bonding groups at their termini. These oligomers were designed such that, upon microphase separation and subsequent crystallization, the dynamic hydrogen bonding interactions become "locked" within crystallization, the dynamic hydrogen bonding interactions become "locked" within crystalline domains. As at result of this association and crystallization the oligomers become virtually chain extended and cross-linked, and exhibit high molecular weight thermoplastic network characteristics. Poly(tetramethylene oxide) glycol of molecular weights varying from 650 to 2900 were end capped with either 1, 2 or 3 ring aryl-ester hard segments. The chain end functionality of the oligomers is either benzyl ester or carboxylic acid. The thermal and physical properties of these oligomers were analyzed by DSC, POM and rheology. The differences between the benzyl ester terminated series, which are incapable of associating, and the carboxylic acid terminated series are dramatic and suggest that the hydrogen bonding imparts a profound effect on the physical properties. Variations in soft segment length also show considerable effects on the thermal and physical properties of the oligomers. The hydrogen bonding and morphology of the materials were further studied by variable temperature infrared and solid state $\sp{13}$C NMR. The later section of this thesis addresses the effects of varying the nature and properties of both the hard and soft segments with the aim of optimizing the degree of phase separation and the structural integrity of the crystalline domains to produce materials with enhanced mechanical properties.