Zugl.: Erlangen, Nürnberg, University, Diss., 2003.

Cette thèse porte sur la réalisation et l’étude de mélanges amidon plastifié/ionomère. L’étude cherche à relier les propriétés thermomécaniques de ces mélanges à leurs morphologies et aux interactions susceptibles d’exister entre les deux matériaux. Le type d’ionomère retenu dérive du poly(éthylène-co-acide méthacrylique). L’amidon de blé plastifié (TPS) est obtenu par déstructuration du granule à l’aide d’un mélangeur interne. Cet instrument permet à la fois de rationnaliser le choix des candidats par un processus de criblage qui repose sur la mesure du ratio des viscosités p des matériaux et de procéder aux mélanges. Dans les conditions où p est proche de l’unité, le nombre capillaire critique est minimal, la morphologie est la plus fine et les interactions sont maximisées. L’étude des propriétés thermiques révèle l’existence d’une interface et la modification de la cristallinité des ionomères par la présence de l’amidon plastifié. Le comportement mécanique des formulations est intermédiaire entre celui d’un composite et celui d’un mélange de polymères. Les modèles montrent une inversion aux forts pourcentages d’amidon plastifié. La morphologie est multimodale, ce qui explique le comportement mécaniques. Elle indique l’existence d’une inversion de phase entre 70% et 90% d’amidon plastifié en masse. Enfin, les interactions font intervenir à la fois la partie polaire et la partie apolaire des ionomères. / This thesis deals with the preparation and the study of plasticized starch/ionomer blends. The study aims to link the thermomechanical properties of these materials with their morphology and the interactions that may exist between the two components. The type of ionomer is derived from poly (ethylene-co-methacrylic acid). The plasticized wheat starch (TPS) is obtained by destructuring the granule using an internal mixer. It makes it possible both to rationalize the choice of candidates by a screening process based on the measurement of the viscosity ratio p of the materials and to carry out the mixtures. Under the conditions where p is close to unity, the critical capillary number is minimal, the morphology is the finest and interactions are maximized. The study of the thermal properties reveals the existence of an interface and the modification of the crystallinity of ionomer due to the presence of TPS. The mechanical behavior of formulations is intermediate between that of a composite and that of a polymers blend. Models show an inversion to high percentages of plasticized starch. The morphology is multimodal, which explains the mechanical behavior. It indicates the existence of a phase inversion between 65% and 90% of weight plasticized starch,. Finally, the interactions involve both the polar and the apolar parts of ionomers.

>Magister Scientiae - MSc / Introduction: Together with bonding to both enamel and dentine, an ideal restorative material would display physical properties similar to that of natural tooth tissue and would not be prone to degradation as a result of the oral environment. This includes changes in colour. Glass ionomer technology has undergone many changes to its original chemistry since it was developed in the early 1970’s. In 1988 resin-modified glass ionomers were introduced and in 2008, nano-ionomers were introduced. As a result of the progression in material sciences and the use of more sophisticated techniques and methods in restorative dentistry, it is possible to accomplish much improved aesthetics and functional durability of a restoration, both anteriorly and posteriorly. However, for as long as aesthetic restorations have been available, and in spite of advances in material structure and performance, one of the greatest challenges facing clinicians still remains that aesthetic restorations have to be replaced relatively frequently as staining and discolouration is a common problem. Aim of the study: The aim of this study was to determine the stainability of four resin-modified glass ionomers and one glass ionomer cement when exposed to a staining broth. Objectives: To record any change in colour before and after exposing the sample with the staining broth using a spectrophotometer, to compare the stainability, to examine the depth of staining using a light microscope and to observe the particle size of the powder and the surface texture using Scanning Electron Microscopy of the four resin- modified glass ionomer cements and one glass ionomer cement. Materials and Methods: Four resin-modified glass ionomers (one nano-ionomer) and one glass ionomer (zinc-reinforced ionomer) were selected. All were shade A2, except for Vitremer™ which was not available in A2. 15 discs of each material were prepared. The discs were 15 mm in diameter and 2 mm in thickness. All the materials were handled and cured according to the manufacturers’ instructions. After curing, only one side of each disc was polished using Sof-Lex™ discs (3M ESPE, USA). The unpolished side of each disc was designated as a matrix finish. The specimens were all immersed in distilled water at 37 °C for one week. They were then immersed in a staining broth for a period of one week and readings were taken after a period of 2 hours, 4 hours, 8 hours, 24 hours and one week. Colour was read on each side of each disc at the indicated intervals with a spectrophotometer. The colour difference was calculated using the CIELAB colour co-ordinates. Sample discs were then sectioned to determine the depth of staining. An additional sample disc of each material was made for observation with the SEM and was therefore not stained. Also, an unmixed sample of each material was prepared for examination with the SEM. Results: In general, for all materials there was an increase in staining when assessed with the colour difference between the baseline colour and the 7 day reading. Ketac™ N100, showed the highest total colour change of 43.84 for the unpolished surface followed by Riva™ which showed the total colour change of 28.55 for the unpolished surface. This was similar to Fuji II LC® which had a total colour change of 28.16 for the unpolished surface. For Vitremer™, the total colour change increased to 18.07 for the unpolished surface. For the unpolished surfaces, ChemFil™ Rock showed the least colour difference from baseline to 7 days (ΔE*ab = 10.45), followed by Vitremer™ (ΔE*ab = 18.07). Both Fuji II LC® and Riva™ Light Cure showed similar colour change from baseline to 7 days for unpolished surfaces (ΔE*ab of 28.16 and 28.55 respectively). Ketac™ N100 showed the highest staining after 7 days in the staining broth with a colour difference of 43.84. For the polished surfaces, the colour change for Fuji II LC® was 25.72 which was similar to Riva™ Light Cure which was 22.44 and Ketac™ N100 which showed a colour change of 22.79 on the polished surface. ChemFil™ Rock showed the least colour change of 17.69 for the polished surface followed by Vitremer™ which showed a colour change of 23.63 for the polished surface. Thus, for both the unpolished and polished surfaces there was a similar staining pattern. Conclusion: In this study it was demonstrated that all products evaluated in this study showed some degree of staining when exposed to a staining broth when evaluated using the ΔE*ab CIELAB colour evaluation. Ketac™ N100 showed the highest colour change compared to the other materials, but the reason for this was not explored. Both Vitremer™ and ChemFil™ Rock showed similar patterns of staining. / 2020-09-01

Thesis (M.S.)--University of Michigan, 1983.

Thesis (M.S.)--University of Michigan, 1996. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1983.

Indiana University-Purdue University Indianapolis (IUPUI) / The functional quaternary ammonium salts (QAS) and their constructed polyQAS or PQAS were synthesized, characterized and formulated into a novel antibacterial glass-ionomer cement. Compressive strength (CS) and Streptococcus mutans (S. mutans) viability were used to evaluate the mechanical strength and antibacterial activity of the cements. Fuji II LC cement was used as control. The specimens were conditioned in distilled water at 37 oC for 24 h prior to testing. The effects of the substitute chain length, loading as well as grafting ratio of the QAS and aging on CS and S. mutans viability were investigated. Chapter 2 describes how we studied and evaluated the formulated antibacterial glass-ionomer cement by incorporating QAS chloride-containing polymer into the formulation. The results show that with PQAS addition, the studied cements showed a reduction in CS with 25-95% for Fuji II LC and 13-78% for the experimental cement and a reduction in S. mutans viability with 40-79% for Fuji II LC and 40-91% for the experimental cement. The experimental cement showed less CS reduction and higher antibacterial activity as compared to Fuji II LC. The long-term aging study indicates that the cements are permanently antibacterial with no PQAS leaching. Chapter 3 describes how we studied and evaluated the formulated antibacterial cements by changing chain length, type of halide, loading, grafting ratio and aging time. The results show that the effects of the chain length, loading and grafting ratio of the QAS were significant. Increasing chain length, loading, grafting ratio significantly enhanced antibacterial activity but reduced CS. The experimental cement showed less CS reduction and higher antibacterial activity as compared to Fuji II LC. The long-term aging study indicates that the cements are permanently antibacterial with no PQAS leaching. There was no significant difference between QAS bromide and QAS chloride, suggesting that we can use QAS bromide directly without converting bromide to chloride. In summary, we have developed a novel PQAS-containing antibacterial glass-ionomer cement. The cement has demonstrated significant antibacterial activities. Our experimental cement is a promising system because the reduced strength of the cement with addition of PQAS is still above those demonstrated by original commercial cement Fuji II LC without any PQAS addition. It appears that the experimental cement is a clinically attractive dental restorative that can be potentially used for long-lasting restorations due to its high mechanical strength and permanent antibacterial function.

Ionomers bearing reactive ion-pair functionality are a novel class of materials that have been prepared. The N-alkylation of N-vinylimidazole by poly(isobutylene-co-isoprene) produced the reactive ionomer product in good yield, through a solvent-borne process. Solvent-free conditions can also be used to produce reactive ionomers by the N-alkylation of N-vinylimidazole by poly(isobutylene-co-para-methylstyrene). Characterization of these derivatives was carried out with the assistance of model compounds, and showed excellent agreement with 1H NMR spectra. These reactive ionomers readily crosslink with peroxide at elevated temperatures and in the absence of peroxide they have excellent thermal stability. The amount of crosslinking can be altered based on the vinyl content of the material, to target various applications. N-alkylation of N-vinylimidazole can be carried out concurrently with a non-reactive N-alkylimidazole to achieve desired vinyl contents and tailor the physical properties of these materials. These materials contain both ionic and covalent crosslink networks, and this hybrid network structure provides these materials with unique crosslink structures and stress relaxation properties. Conventional rubber fillers are compatible with these novel reactive ionomers. Carbon black and precipitated silica have no adverse effects on the peroxide crosslinking of the elastomers and a constant peroxide loading can be used regardless of the filler loading. Payne analysis shows good filler dispersion at low filler loading; however, there is some evidence of reticulate filler network formation at high filler loadings. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-03-31 21:12:46.618

As atmospheric carbon dioxide (CO2) levels continue to rise due to anthropogenic fossil fuel utilization, the need to develop and employ alternative energy carriers becomes more and more critical. In recent years, interest in hydrogen (H2) has significantly increased as it is a clean and sustainable, alternative fuel, which can be both produced and utilized without greenhouse gas emissions; H2 can be produced via water electrolysis powered by renewable energy sources (RES), such as wind and solar energy, then, H2 can be utilized as a fuel in a hydrogen fuel cell, emitting only water as a by-product. Not only is H2 a clean alternative fuel, but it also provides an economically feasible way of storing renewable energy so that RES supply can be better regulated according to demand. Of the existing water electrolysis technologies, not many offer the ability to produce hydrogen both efficiently and at low cost. The alkaline environment of the more commonly employed traditional alkaline electrolyser allows for the use of non-noble metal electrocatalysts, as well as inexpensive cell materials. This process however suffers from an inefficient cell design. Conversely, the proton exchange membrane water electrolyser (PEMWE) utilizes a solid polymer electrolyte membrane, which allows for a compact, low resistance cell design. However, the harsh acidic environment of this device requires expensive platinum group metal (PGM) catalysts and expensive cell components. Anion exchange membrane water electrolysis (AEMWE) is a promising technology for low-cost, efficient H2 production as it combines the compact cell design of the PEMWE with the favourable alkaline environment of the traditional alkaline electrolyser. The electrochemical water splitting process is limited by the kinetically unfavourable oxygen evolution half-cell reaction (OER), which requires expensive rare catalysts such as iridium, to efficiently carry out the reaction. Nickel (Ni) is a promising inexpensive and abundant catalyst for the OER in alkaline media, due to its high activity and corrosion resistance. A significant increase in OER activity can be achieved by iron (Fe) incorporation into Ni catalysts. The addition of ceria (CeO2), a mixed ionic-electronic conductor with favourable oxygen storage and release properties, can also have a positive effect on catalytic performance. While developing electrocatalysts for improved OER performance is important, evaluating the studied materials as anodes in practical AEMWE devices is imperative as it accounts for the efficiency of the catalysts in electrode layers formed using an anion exchange ionomer (AEI). An AEI is a solid polymer electrolyte that serves as a binder for the particles as well as a hydroxide ion conductor in a catalytic layer of an AEMWE. The main objectives of this thesis are to (i) develop highly active NiFe-based nanoparticle (NP) catalysts with and without CeO2 for the promotion of the OER in AEMWE devices, and (ii) study the effects of commercial AEI type and amount on the efficiency of the produced NiFe-based particles in AEMWE anodes. These objectives will help further understand the behaviour of Ni-based catalysts in AEMWE systems, as well as the effects that catalyst-ionomer interactions can have on anode efficiency in carrying out the OER. The nanoparticles developed in this work were synthesized by an easily scalable chemical reduction method in ethanol using sodium borohydride. Results show that Ni NPs, which are around 4-6 nm in size, with 10 and 20 at% Fe, provide the highest OER performance. Incorporating small amounts of CeO2 into the NiFe materials results in better charge and mass transfer of the catalysts, however it introduces an additional ohmic resistance, which prevails over any OER-promoting interactions between NiFe and CeO2. The best NiFe-based catalysts with and without CeO2 were evaluated as anodes in a single cell AEMWE in combination with the commercial Fumatech Fumion® ionomer as well as the commercial Ionomr Innovations AemionTM ionomer. The single-cell AEMWE analysis of the various catalytic layers shows that Ni90Fe10 with 15 wt% Fumion® shows the best catalytic performance of 1.72 V at 0.8 A cm-2 in 1 M potassium hydroxide (KOH) at 50°C. Ni90Fe10 is also the most stable under operating conditions in comparison to the other tested Ni-based materials. While it was found that using 7 wt% AemionTM provided similar catalytic activity to 15 wt% Fumion®, results show that the AemionTM ionomer interacts with NiFe to inhibit the formation of NiOOH, the OER active phase. The results of this work highlight the complex interactions between Ni-based nanoparticles and anion exchange ionomers towards the OER and provide possible directions for future research and development in high performing Ni-based anodes for AEMWE.

Semicrystalline ionomers are an important class of polymers that are utilized in a wide range of applications. The particular end-use applications of these materials are determined by their chemical, physical, and thermomechanical properties which are directly related to their crystallization behavior. It is therefore critical to identify structure-property relationships for these materials. Sulfonated syndiotactic polystyrene (SsPS) is used as a model semicrystalline ionomer and two approaches are utilized to control the rate of crystallization of the SsPS ionomer in the presence of ionic aggregates. The first approach investigates the effect of the incorporation of nanoscale particles, montmorillonite clay, on the crystallization behavior of SsPS. The morphology of the ionomer clay hybrids were studies via TEM and WAXD while the crystallization behavior of SsPS in the presence of the clay was evaluated using DSC. It was found that the SsPS matrix containing 5 wt.% organically-modified clay crystallized more rapidly than the sPS homopolymer containing the same clay content. This behavior is attributed to the presence of homogenously dispersed nanoscale clay platelets that act as nucleation sites distributed throughout the ionomer matrix. The second approach that employed involved the manipulation of SsPS ionomer architecture via a controlled placement of the ionic sulfonate groups along the polymer backbone. A post-polymerization sulfonation technique was developed to place the sulfonate groups along the homopolymer backbone in a non-random fashion leading to a pseudo-block ionomer architecture. The crystallization behavior of the non-randomly sulfonated SsPS ionomer is compared to randomly sulfonated SsPS using differential scanning calorimetry. The morphologies of the two ionomers were studied using SALLS and SAXS. We have found that the non-randomly sulfonated SsPS ionomer crystallizes much more rapidly than the randomly sulfonated ionomer. The more rapid crystallization behavior of the non-random ionomer to the presence of longer sequences of unsulfonated homopolymer that are able to readily organize into crystalline structures than the random SsPS ionomer containing the same ionic content. / Ph. D.