Styrene/acrylonitrile (SAN) copolymers with excellent chain-end fidelity and low polydispersity Mw/Mn (1.10 – 1.30) were synthesized by nitroxide mediated polymerization (NMP) in dimethylformamide (DMF) solution with a succinimidyl ester (NHS) terminal group from the so-called SG1 nitroxide residue. These copolymers were thermally stabilized by removing the N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl) nitroxide] (SG1), and then modified to form primary amine end-functional SAN (SAN-NH2). Homogeneous coupling reactions and Fourier-transform infrared spectroscopy (FTIR) indicated that the amine group was effectively placed at the chain end. SAN-NH2 was reactively blended with maleic anhydride grafted poly(ethylene) (PE) at 20 wt.% loading at 180 °C and the resulting morphology was compared against the non-reactive blend. Scanning electron microscopy (SEM) indicated finer SAN domains ~ 1 μm which were thermally stable upon annealing in the reactive case. The dispersed SAN domains were reoriented using a channel die to impart elongated domains with aspect ratios ~ 14, which would be desirable for barrier materials. / Les copolymères de styrène/acrylonitrile (SAN) avec des excellente fidélité en bout de chaîne et des faible polydispersité Mw/Mn (1,10 - 1,30) ont été synthétisés par polymérisation des nitroxydes (NMP) dans une solution de diméthylformamide (DMF) avec d'ester de succinimidyle (NHS) groupe terminal de l'soi-disant SG1 résidus nitroxyde. Ces copolymères ont été stabilisée thermiquement par élimination du groupe N-tert-butyl-N-[1-diéthylphosphono-(2,2-diméthylpropyl) nitroxyde] (SG1), et ensuite modifiée pour former une amine primaire à fonctionnalité en bout de chaine des copolymères (SAN-NH2) . Réactions de couplage homogènes et transformée de Fourier spectroscopie infrarouge (FTIR) a indiqué que le groupe amine a effectivement été placé en bout de chaîne. SAN-NH2 a été réactive mélangée avec l'anhydride maléique greffé poly(éthylène) (PE) au chargement de 20% en poids à 180 °C et la morphologie obtenue a été comparée à la mélange non réactif. Dans le cas réactif, microscopie électronique à balayage (MEB) ont indiqué plus fines domaines de SAN ~1 um qui étaient stables thermiquement après recuit. Les domaines dispersés SAN ont été réorientés en utilisant un dé canal pour donner domaines allongés avec des rapports d'aspect ~14, ce qui serait souhaitable pour des matériaux barrières.

There is a great need to develop new polymer foam systems that combine the advantages of polyurethane foams (low cost, ease of processing, desirable physical properties) with nonflammability and thermal stability which polyurethanes lack. In this project we address this need by synthesizing novel polymer networks with a substantial content of nonflammable elements. Specifically most of the pendant hydrogens have been eliminated (or replaced with fluorine), and a substantial fraction of the carbon atoms are replaced with oxygen, phosphorus, and nitrogen. Other elements such as Ca, Mg, Al, Sb, V, and B are also incorporated in the polymer network to enhance nonflammability. The selected phosphorus compounds are in their highest oxidation state (+5) and the nitrogen is present in the form of five or six-member heterocyclic rings. Following these guidelines, several rigid, semi-rigid, and flexible, foamed-in-place foams with outstanding nonflammability and thermal stability have been developed.

Measuring the zero-shear viscosity of a molten polymer is not at all straightforward. Available rheometers are unable to operate at shear rates low enough to measure this important property, especially for polymers that have a very broad molecular weight distribution or a high degree of long chain branching. A new falling ball viscometer, the Magnetoviscometer (MVM), has recently been developed in Austria for the measurement of melt viscosity at very low shear rates. The primary objective of the research was to evaluate this instrument as a tool for the routine measurement of the zero-shear viscosity. Another objective was to develop a reliable and convenient method to prepare samples. Experiments performed near the maximum allowable stresses for various resins are in good agreement with dynamic data obtained using a rotational rheometer. The MVM allows for the measurement of viscosity in a range of shear rates not accessible to most rheometers.

The thermolysis of mixtures of polyethylene and polystyrene was investigated. Overall liquid production for the mixture was above the values predicted from individual polymer reactions. No detrimental effects on the styrene production were evident, as over 50% of the initial polystyrene charge was converted to styrene for polystyrene and for mixtures. There were, however, some differences in the secondary products. No incorporation of one polymer onto another was observed, either in the liquid or the residue. / Different reaction conditions were examined. It was determined that using a single reaction temperature (445$ sp circ$C) was as effective at separating the aromatic and aliphatic products as using two different reaction temperatures. / Polystyrene was found to catalyze the thermolysis of polyethylene. Conventional catalysts (Mordenite and FCC zeolite) affected the overall production and product distributions for mixtures and polyethylene, while only changing the product distribution for polystyrene. Hydrogen in the purge gas only slightly decreased the ratio of 1-alkenes to n-alkanes. / Recycled plastics yielded results similar to virgin polymers, although overall liquid production was decreased (probably due to the additives present in the plastics).

This is an investigation of the response of a double fixed-ended pultruded fiberglass tube subjected to large lateral displacements, in both quasi-static and dynamic conditions. The experiments yield a two-mode response of the tubing to loading. The first mode, referred to as the local mode, is dominated by crushing of the cross-section. The second mode, referred to as the global mode, consists of beam flexure and shear components. An analytical model, based on deformed geometry, has been developed to predict the response of the tubing under quasi-static loading conditions. Model results compare well with experiments and minimal computation time is required. Dynamic tests demonstrate a significant rate dependency, which is more pronounced in the globally-dominated portion of the behavior. The model has been used to demonstrate that steel tubing, commonly used as beams or energy absorbers, may successfully be replaced by fiberglass tubing produced by pultrusion or filament winding.

The effect of pressure on the viscosity of polyethylenes was studied using a newly developed high-pressure, sliding-plate rheometer. The rheometer subjects the sample to a homogeneous pressure and temperature at levels up to 70 MPa and 225°C. Simple shear is generated in the sample, and the resulting shear stress is measured locally in the center of the sample by means of a shear stress transducer. Viscosity curves were generated at four pressures from 0.1 to 70 MPa, and it was found that the pressure data could be shifted onto the ambient pressure curves by means of a pressure shift factor. The viscosity increases exponentially with pressure. Long chain branching increases the pressure sensitivity, but the polydispersity has little effect. / The effect of pressure on the creep behavior of polyethylenes was also studied. It was observed that pressure decreases the creep compliance. Careful tuning the controller is required to obtain reliable data when operating the rheometer in the creep mode.

The micellization of polystyrene based block copolymers was investigated in aqueous and in organic media. Micelles formed from polystyrene-b-poly(sodium acrylate) (PS-b-PANa) in sodium chloride solutions were investigated by static light scattering (SLS). The aggregation numbers (N$ rm sb{agg})$ were influenced by low salt concentrations ($<$0.10 M) and they were essentially independent of the soluble block lengths. The core radii ($ rm sb{e}$ agreed well with previous solid state results on similar samples studied by small-angle X-ray scattering (SAXS). It was thus concluded that no supermicellar aggregates were present and that the cores were solvent free. / A method to evaluate the critical micelle concentrations (cmc's) of block copolymer micelles by SLS was developed to account for the effects of polydispersity on the cmc. It was found that for block copolymers which have a significant dependence of the cmc on the insoluble block length and which are polydisperse only the present approach was able to evaluate the cmc. / The micellization of PS-b-PANa and PS-b-poly(acrylic acid) (PS-b-PAA) block copolymers were investigated in organic solvents. The cmc's were found to range from $1 times10 sp{-7} { rm to} 5 times10 sp{-9}$ M for insoluble block lengths ranging from 2.6 to 18 units. The N$ rm sb{agg}$ and R$ rm sb{e}$ values for four PS-b-PANa series in tetrahydrofuran, were found to be a function of the length of both blocks. The effect of the degree of neutralization of the PAA block on micellization was probed by SLS and SAXS; micelle formation was found to commence at 5% neutralization. The distribution of water between toluene and the polar cores of block ionomer and sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles was investigated by proton chemical shift measurements as a function of temperature. The amount of water solubilized and the thermodynamic parameters of transfer were found to be a function of the core nature.

Natural Montmorillonite was modified with thermally stable phosphonium surfactants to produce new organoclays for the production of polymer nanocomposites. The organoclays were characterized to determine thermal stability, basal spacing, and the surface energy at room temperature and at the processing temperature. Polystyrene (PS)/organoclay nanocomposites were prepared by melt compounding, using three different PS resins. Experimental data were obtained to elucidate the influences of temperature and molecular weight and structure of the surfactant on the surface energy of the organoclays. The phosphonium-based organoclays exhibited better thermal stability than commercially available ammonium-based organoclays. The basal spacing was similar to that found in commercially available organoclays. Transmission electron microscopy (TEM) showed that the degree of dispersion of the various organoclays in nanocomposites was related to the Hamaker constant of the organoclay at the processing temperature. Significant improvement in the degree of dispersion was realized, when blends of polystyrene with a styrene- maleic anhydride (SMA) copolymer were used. It appeared that delamination in the SMA systems was achieved directly without undergoing an intermediate intercalated structure. The influence of organoclay concentration on flexural modulus of PS- organoclay nanocomposites was determined, using the Halpin-Tsai and Hui-Shai models. The predictions were in good agreement with experimental results. The modulus of PS nanocomposites correlated well with the work adhesion at room temperature, in agreement with the equation of Shang. Barrier properties showed reasonable agreement with the predictions of models reported in literature. However, the values of aspect ratios predicted by the models were quite different from those observed experimentally. The permeability of nanocomposites to oxygen correlated with both the Hamaker constant A131 at the processing temperature / De la montmorillonite naturelle a été modifiée avec des surfactants de phosphonium qui sont thermiquement stables pour objectif de produire de nouvelles organoargiles pour la production de nanocomposites polymériques. Les organoargiles ont été caractérisées pour déterminer la stabilité thermique, l'espacement basal et l'énergie superficielle à température ambiante et à la température de préparation. Des nanocomposites de polystyrène (PS) et organoargile ont été préparés en fondant le PS, avec trois différentes résines de PS. On a évalué l'influence de la température, de la masse molaire et de la structure des surfactants sur l'énergie superficielle des organoargiles. Les organoargiles préparées avec des surfactants de phosphonium ont démontré une meilleure stabilité thermique que les organoargiles commerciales préparées avec des surfactants d'ammonium. L'espacement basal a été similaire à celui des organoargiles commerciales. La microscopie électronique en transmission a démontré que le degré de dispersion des organoargiles dans les nanocomposites est en relation avec la constante de Hamaker de l'organoargile à la température de préparation. Le degré de dispersion de l'argile a été amélioré quand un mélange de polystyrène avec un copolymère de styrène et d'anhydride maléique (SAM) a été employé. Apparemment, la delamination dans les systèmes de SAM a été réussie directement sans avoir une structure intercalée intermédiaire. On a déterminé l'influence de la concentration d'argile sur les propriétés mécaniques des nanocomposites de PS en utilisant les modèles de Halpin-Tsai et Hui-Shai. Les prédictions ont été en accord avec les résultats expérimentaux. Les modules des nanocomposites de PS sont bien corrélés avec le travail d'adhésion à la température ambiante, selon l'équation de Shang. Les propriétés de barrière ont été mesurées et sont en accord avec les prédictions des$

A number of concentrated high molecular weight narrow distribution polystyrene solutions were investigated using a sliding plate rheometer. An in-depth study of the wall slip of these solutions had to be conducted to determine the range of conditions where this phenomenon occurred. It was found that the critical stress for the onset of slip depends on the surface of the substrate. Step strain experiments allowed the determination of the ratio of the second to the first normal stress difference, which was found to have values of up to $-$2. Gradients in the normal stress differences are believed to be the cause of an observed secondary flow. Large amplitude oscillatory shear experiments were carried out over a wide range of frequency and strain rate amplitude making it possible to construct response surfaces. All three solutions revealed a linear plateau that extended to higher strain rate amplitudes as the frequency increased. It was also found that the loss modulus has a maximum at the onset of nonlinear behavior. The higher harmonics describe the solutions' nonlinearity, and it was found that their qualitative behavior mirrors that of the first harmonic. The effect of molecular weight was assessed for the tricresylphosphate solutions. It was found that the principal harmonic exhibits the expected behavior; as the molecular weight increases, the elasticity of the solution increases. The higher harmonics followed no clear trend. / The Doi-Edwards theory and Wagner model were compared to experimental data for all solutions, and both models fell short in quantitative predictions, the Doi-Edwards theory being worse due to its relaxation spectrum. Optical measurements on the tricresylphosphate solutions allowed the determination of the third normal stress difference in LAOS. It was found that the magnitude was independent of molecular weight. However, the "higher" harmonics were found to be dependent on molecular weight. As molecular weight increases, they extend to higher frequencies.

Interfacial tension is one of the most important parameters that influence the morphology of polymer blends. However, few data are available regarding interfacial tension between polymers due to experimental difficulties. / Two devices, one based on the pendant drop method and another based on the spinning drop method, were constructed in this work to conduct an experimental study of interfacial tension between polymers. With both instruments, it was possible to view the drop in real time and to calculate the interfacial tension on-line. The following aspects were considered: special syringe design, the necking and capillary effects, in the pendant drop method, and sealing of the rotating tubes and density measurement in the spinning drop method. The two devices were shown to be reliable and complementary. A method to infer interfacial tension from transient measurements was suggested. / Interfacial tension was measured for different polymer pairs. The effects of temperature, molecular weight, bimodal blending and molecular weight distribution were evaluated. The effect of adding compatibilizers was also studied. Surface analysis of the interfaces was performed using E.S.CA. to explain the experimental results. / The experimental results were compared with the predictions of lattice theories and the square gradient theory. A strategy to evaluate the Flory-Huggins interaction parameter between polymers was developed. When this strategy was employed, theoretical predictions and experimental data showed good agreement for the influence of temperature and molecular weight on interfacial tension. However, the theory could not predict the effect of polydispersity on interfacial tension.