<p>Atom transfer radical polymerization (ATRP) has proven to be a powerful technique to obtain polymers with narrow polydispersities and controlled molecular weight. It also offers control over chain-ends. The technique is the most studied and utilized of thecontrolled/”living” radical polymerization techniques since a large number of monomerscan be polymerized under simple conditions. ATRP can be used to obtain polymer graftsfrom multifunctional substrates. The substrates can be either soluble (i. e. based ondendritic molecules) or insoluble (such as gold or silicon surfaces). The large number ofgrowing chains from the multifunctional substrates increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems, andsuppress side-reactions such as termination, the concentration of propagating radicalsmust be kept low. To elaborate such a system a soluble multifunctional substrate, based on 3-ethyl-3-(hydroxymethyl)oxetane, was synthesized. It was used as a macroinitiatorfor the atom transfer radical polymerisation of methyl acrylate (MA) mediated byCu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. Since mostsolid substrates are sensitive to the temperatures at which most ATRP polymerisations are performed, lowering the polymerization temperatures are preferred. ATRP at ambienttemperature is always more desirable since it also suppresses the formation of thermally formed polymer. The macroinitiator contained approximately 25 initiating sites, which well mimicked the conditions on a solid substrate. The polymers had low polydispersity and conversions as high as 65% were reached without loss of control. The solid substrateof choice was cellulose fibers that prior to this study not had been grafted through ATRP.As cellulose fibers a filter paper, Whatman 1, was used due to its high cellulose content.The hydroxyl groups on the surface was first reacted with 2-bromoisobutyryl bromidefollowed by grafting of MA. Essentially the same reaction conditions were used that hadbeen elaborated from the soluble substrate. The grafting yielded fibers that were very hydrophobic (contact angles>100°). By altering the sacrificial initiator-to-monomer ratiothe amount of polymer that was attached to the surface could be tailor. PMA with degreesof polymerization (DP’s) of 100, 200 and 300 were aimed. In order to control that thepolymerizations from the surface was indeed “living” a second layer of a hydrophilicmonomer, 2-hydroxymethyl methacrylate (HEMA), was grafted onto the surface. Thisdramatically changed the hydrophobic behavior of the fibers.</p> / QC 20100524

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$\sp2$H-NMR is a powerful spectroscopic technique for investigating dynamics in solids. to extend the range of motional rates that can be quantitatively investigated, a new approach for measuring the quadrupolar spin-lattice relaxation time $T\sb{1Q}$ was developed. This uses a Broadband Jeener-Broekaert (BBJB) sequence with echo-detection, which avoids the frequency-discriminated excitation profile and spectral baseline distortion intrinsic to the conventional Jeener-Broekaert (JB) experiment. By combining the BBJB experiment with an Inversion-Recovery sequence with Quadrupole-Echo detection (IRQE), two independent longitudinal relaxation times, $T\sb{1Q}$ and $T\sb{1Z}$, can be measured. Spectral densities of motion $J\sb1(\omega\sb{o}$) and $J\sb2(2\omega\sb{o}$) are extracted from these relaxation times. The new approach was demonstrated on a nematic liquid crystal binary mixture of 4-methyl-4$\sp\prime$-cyanobiphenyl-d$\sb{11}$ (1CB) and 4-n-pentyl-4$\sp\prime$-cyanobiphenyl-d$\sb6$ (5CB). Measurements on mixtures containing 10 and 25 mol% 1CB revealed that rotational motion can be described by the third rate model and the correlation times and activation energies of 1CB and 5CB are concentration independent. In hexamethylbenzene, it was demonstrated that the orientation dependence of spectral densities provides geometric and kinetic information. This technique works well for motions which are in the fast regime ($k\ge10\sp7 s\sp{-1}$) and contribute to relaxation. at ambient temperature, the experimental data were fit by a simulation which included simultaneous threefold and sixfold rotations, with geometric distortions of the electric field gradient tensors of the methyl group. The best-fit jump rates for threefold methyl rotation was $k\sb3 = 5.0\times10\sp{11} s\sp{-1}$ and sixfold aromatic rotation was $k\sb6 = 3.85\times10\sp8 s\sp{-1}$, with out-of-plane and in-plane distortions of 2.5$\sp\circ$ and 1.2$\sp\circ$ respectively. Relaxation times of the bisphenol-A polycarbonate (BPA-PC) and its monomer (BPA) were measured between 250K to 400K. The data were fit to several dynamic models. Simple threefold methyl rotation accounts for the spectral density anisotropies of BPA but not those of the polymer BPA-PC. Inclusion of a semilogarithmic distribution of jump rates, $k\sb3$, improved the agreement qualitatively but not quantitatively. Modulation of threefold methyl jumps by libration of the $C\sb{3V}$ axis was treated with the Stochastic Liouville formalism. Best agreement is found if the two motions are correlated. Activation energies for methyl group rotation are 19.2 $\pm$ 2.0 kJ/mol and 13.0 $\pm$ 0.8 kJ/mol in monomer and polymer respectively.

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Polyamide-11 (PA11) is a polymer of the Nylon family whose monomer is obtained from the castor bean, a renewable resource. It is widely used in offshore oil and gas production as a non-rigid flexible pipe liner, allowing for oil and gas transport from the wellhead to floating platforms for processing. The degradation of PA11 over time may lead to the pipe's failure, with possibly catastrophic results which include loss of life. Until now, the characterization of the degredative process has been limited to laboratory studies of the effects of water and temperature on the rate and degree of hydrolysis. In this dissertation, a more exact model than those proposed in the literature thus far is defined and used to quantify the effects of temperature on the rate and degree of PA11 hydrolysis. This is performed using accelerated aging experiments in the lab which are evaluated by a primary means of molecular weight determination, size exclusion chromatography---multiple angle laser light scattering (SEC-MALLS). The effects of methanol and ethanol, used in the industry to control solid hydrate formation, are then characterized with respect to concentration and temperature, a topic which has not yet been addressed in the literature. Also novel to this work is the discovery of the effects of acetic acid, valeric acid, and 3-cyclopropionic acid on the rate and degree of PA11 hydrolysis. While these acids are present in the offshore oil and gas environment, acetic acid is the most common, and has been identified as a serious factor affecting degradation. The effects of acetic acid on rate and degree of hydrolysis are incorporated into the temperature dependence described above, and adapted to a model well suited for characterizing the degradation of PA11 in the changing temperature environments found in the field. By characterizing coupons removed from PA11 pipes in oil production fields in various parts of the world, the model is tested and used to predict aging of PA11 pipe. The model is shown to be effective at predicting degredation for times greater than ten years, which has never before been described. The effects of annealing coupled with decline in molecular weight on PA11 mechanical properties in accelerated aging experiments versus aging in the field environment is discussed. These contributions to understand and predict the aging of PA11 flexible pipes are central to increasing the safety of offshore oil and gas production, a topic that today is vastly important.

Carbon-13 NMR spectroscopy was used to investigate the microstructures of poly(vinyl acetate) prepared by solution polymerization in benzene. A series of aromatic compounds was synthesized in order to model the structures formed via chain transfer to solvent. The peaks near 126.5 and 128.5 ppm in the spectra of the polymer samples were assigned to a 1-phenyl-(2n + 1)-multi-acetoxyalkane (where n = 1, 2, 3, etc.) microstructure. The concentration of that structure obtained from NMR spectra was correlated with the concentration calculated from reported kinetic data.;Chain transfer to benzene was shown to occur by addition of the macroradical to benzene, followed by rearomatization involving loss of a hydrogen atom. No evidence was obtained for a transfer mechanism involving hydrogen abstraction from benzene, and the copolymerization of benzene with vinyl acetate also was shown to be absent. The transfer mechanism actually established accounts for the unexpectedly large transfer constant of benzene in vinyl acetate polymerization. General mechanisms are proposed for the solution polymerization of vinyl acetate in aromatic solvents.

Cyclophanes are a family of bridged cyclic aromatic compounds that have found extensive applications in host-guest chemistry, molecular recognition, biomimetics and most recently as precursors in ring-opening polymerizations.;This research presents the synthesis of several novel cyclic arylene ether oligomers, based on 1,3-bis(4-fluorobenzoyl) benzene and 3,3{dollar}\sp\prime{dollar}-methylene diphenol and 3,3{dollar}\sp\prime{dollar}-(ethylene dioxy) diphenol, and their characterization by LC-MS/MS, 1-D {dollar}\sp1{dollar}H-NMR and x-ray crystallography. Electrospray ionization (ES) along with MS/MS was used to characterize cyclic oligomers of molecular weight up to 1600 Da. The thermal properties of these cyclic oligomers were studied by differential scanning calorimetery (DSC) and thermal gravimetric analysis (TGA).;These cyclic oligomers were synthesized in high yield by regulating the reaction time, concentration, temperature and solvent systems. The relevance of reaction conditions was investigated by selected reaction monitoring (SRM).;Molecular dynamics and potential energy calculations were also carried out to understand the molecular characteristics of the bisphenols that lead to the formation of these cyclic species. Furthermore, the molecular modeling studies assisted in predicting the conformations of the small macrocyclic rings. The predicted structures indicted the cavity size and the relative orientation of the oxygen atoms.