Indiana University-Purdue University Indianapolis (IUPUI) / This investigation examined the relationships among light cured glass ionomer liner, light cured glass ionomer base, and composite resin material in the reattachment of fractured anterior tooth fragments. Seventy-five bovine incisor teeth were fractured and luted back together with three different materials (Universal Bonding Agent/TPH Composite Resin; VariGlass VLC Liner; VariGlass VLC Base, LD Caulk Div Dentsply Int Inc, Milford, DE) of equal number. The reattached fragments were subjected to thermocycling with a 40° C differential and then were loaded until the force required to detach the fragment was reached. The mean dislodgment strengths were 36.8 (± 25.6)kg for the composite resin, 36.4 (± 26.7)kg for the glass ionomer base, and 31.4 (± 29.S)kg for the glass ionomer liner. Analysis of variance demonstrated no significant difference between the three groups at p≤0.05. Also examined was the type of fracture after reattachment. Of the sixty-five teeth that were studied microscopically, 84.6 percent of the fractures were cohesive in nature, thus a breakdown occurred within the material itself.

Renewable energy applications (i.e. fuel cells, flow batteries, electrolyzers) have been at the forefront of green energy and environmental research over the past couple of decades and the research associated with them has skyrocketed due to changes in funding and incentives. The extensive research over the years have resulted in higher efficiency and longer lasting devices for renewable energy applications, but there is still a major bottleneck that all these devices share; the ion-exchange membrane (IEM). The development of polymer ion-exchange membranes has been very beneficial for these devices as they allow for higher working temperatures and increase the longevity and efficiency of said devices. IEM research can be summed up into two major types of membranes; proton- and anion-exchanging. Of these materials, proton-exchanging membrane (PEM) are well established and studied due to how long they have been manufactured and the ease of manufacturing. There has been a variety of different PEMs developed and tested, but none have been commercialized as heavily or used as universally as Nafion® (developed by DuPont in the 1960s) although it still suffers from setbacks like its high cost, low working temperatures and its low tolerance for fuel impurities. On the other hand, anion-exchange membranes (AEM) have become popular in this field of study as they boast a non-acidic substitute as well as more efficient oxygen reduction reactions allowing for operation without the use of expensive catalysts. AEMs are first in line to replace commercial PEMs like Nafion®, the major bottleneck being their ionic conductivities. Pairing the structural characteristics of PEMs with the efficient and more cost effective AEMs we sought out to design and synthesize new IEMs to compete with current commercial membranes. By using ring opening metatheses polymerization (ROMP) we have designed and developed numerous hydrocarbon polynorbornene derivative membranes with the intention of incorporating amino-phosphine ion exchange groups (IEG) to compete with current IEMs in both efficiency and cost with the major application of fuel cells and flow batteries in mind. We also performed different modifications to the initial membranes such as crosslinking and alkyl chain addition to increase the mechanical strength and mitigate the degradation of the membranes. Using results gathered from developing polynorbornene IEMs, we pivoted to another multitude of membranes, this time focusing on the PEM capabilities of fluorinated polymers instead of their hydrocarbon alternatives for use in redox flow batteries with the main goal of decreasing electrolyte crossover, therefore increasing the longevity of the devices. Several new IEMs were designed as composite membranes of Nafion® and aromatic organic IEGs and synthesized to compete with the current commercial IEMs while testing the effect of different aromatic IEGs on the salt permeability and mechanical strength of the membrane. Synthesis of a stable IEM with good electrolyte crossover and conductivity properties was achieved by combining a grafted Nafion® backbone with 2-phenylbenzimidazole side chains containing a long hydrocarbon chain to facilitate hydrophobicity and increase mechanical strength. These composite membranes take advantage of the imidazole’s highly stable chemical backbone and proton exchanging properties allowing it to withstand highly acidic and oxidative environments as well as relying on benzimidazoles tight packing to reduce electrolyte permeability throughout the membrane.

Indiana University-Purdue University Indianapolis (IUPUI) / The search for an orthodontic bonding adhesive that has chemical adhesion to enamel and releases fluoride into the oral environment has led to experimentation with glass ionomer cements. This study compared the tensile bond strength of eight different orthodontic bracket base designs in vitro and assessed the amount of adhesive remaining on the bracket pad after debonding. Each bracket base design included in this study had unique characteristics warranting their inclusion. The groups contained brackets with 60, 80, and 100 gauge mesh pads; 100 gauge mesh sandblasted pads; perforated metal bases; Micro-Lock™ photo-etched bases; Dyna-Lock™ integral bracket/bases; and ceramic silane-coated bracket pads. Groups contained 20 to 22 specimens that were bonded to bovine incisor teeth embedded in a self-curing acrylic block that could be held in the testing machine. Pre-encapsulated glass ionomer cement (Ketac-Fil™) was the experimental adhesive. The adhesive was mixed according to the manufacturer's instructions in a dental amalgamator. The specimens were thermocycled between water oaths of 15°C and 55°C. The specimens spent 30 seconds in each bath for a total of 2,500 cycles and were stored in a humidor until debonding. After 14 days, the specimens were subjected to a tensile force using an Instron mechanical testing machine until failure occurred. The Micro-Loc™ photo-etched base had significantly higher mean tensile bond strength (p<0.05) than all other brackets tested. The ceramic brackets were unable to be tested due to the extremely weak bond strength which did not allow preparation of the samples for debonding. Following debonding, the percentage of adhesive remaining attached to the bracket base was determined using a grid in the ocular of a light microscope. In general, the site of bond failure involved the base/adhesive interface. The Dyna-Lock™ integral bracket/base and 80 gauge mesh base had a greater mean percent of adhesive remaining attached to the base. (Dyna-Lock™ 45 percent and 80 gauge mesh 43 percent vs. all other < 20 percent.) The results indicate that the bracket base design can influence the bond strength when GIC is used as an orthodontic adhesive and suggests that development of GIC with increased fracture toughness might increase bond strength.

No description available.

Ionic polymer transducers (IPT) are a class of electroactive polymer devices that exhibit electromechanical coupling through charge transport in ionomeric membranes that contain a charge mobilizing diluent and are interfaced with conducting electrodes. Applications of these active materials have been broadly developed in the field of actuators and sensors. Advances in fundamental understanding of IPT performance mechanisms and tuning of the device components has primarily focused on transducers constructed with the commercial ionomer Nafion® due to its overall stability, high ionic conductivity, and availability. The much smaller number of studies conducted with non-perfluorosulfonated ionomers concentrated on changes in chemical composition to address processability, price, ionic conductivity, and hydrated modulus of the final IPT. Also, nearly all ionic polymer transducers operated with water as the diluent until the recent successful development of IPTs with ionic liquids. The objective of this research is to increase the understanding of electromechanical transduction in ionic polymer transducers through the synthesis and characterization of novel branched ionomers. Controlled branching is achieved in sulfonated polysulfones (sBPS) through employment of an oligomeric A₂ + B₃ step-growth polymerization. Structure – property relationships are established for a series of linear and branched sulfonated polysulfones to resolve the effects of polymer topology and charge content on ionomer properties such as hydrated modulus and ionic conductivity. Furthermore, the variation of these parameters is investigated in the presence of ionic liquids as a function of ionic liquid uptake using two methods for introduction of the diluent. One of those methods, based on casting of IPT components in the presence of the ionic liquid, was applied to the Direct Application Process to produce a controlled set of IPT electrodes and transducers to investigate percolation effects of RuO₂ on the device's electrical properties and actuation characteristics. Equivalent circuit modeling of the component and transducer electrical impedance accurately modeled variations in contributing processes and material interfaces to estimate the evolution of effective capacitance based on the electrode composition. Combination of optimized electrode composition, ionic liquid uptake, and the series of linear and branched sulfonated polysulfones allowed for fabrication of a tailored set of novel ionic polymer transducers. Effects of the fabrication process on the ionic conductivity of the membranes and transducers are evaluated using electrical impedance spectroscopy, which also allowed for equivalent circuit modeling to calculate effective capacitance for the series of IPTs that varied in composition, topology, and uptake for both types of fabrication processes. The transducers described in this dissertation are the first IPTs to be designed and actuated with novel ionomers, specifically linear and branched sulfonated polysulfones, in the presence of ionic liquids. Use of sulfonated polysulfones allowed for realization of transducers with high uptakes of the ionic liquid diluent that retained significant hydrated modulus on the order of 2 GPa. Characterization of electromechanical transduction for the series of sBPS – IPTs was demonstrated in cantilever bending through frequency response analysis and step responses in the time domain to low input voltages. Both the ion content and polymer topology of the sBPS ionomeric matrix demonstrated a significant effect on the final actuation performance in relation to variations in charge transport. Also, IPTs constructed with a co-diluent swelling method which emphasized the formation and stability of the ionomer's charge transport pathway demonstrated the greatest actuation responses, up to a peak-to-peak strain of ~0.45 % and strain rates on the order of 0.1 % / s while producing significant blocked force (180 N/Vm). Combination of these actuation performance metrics resulted in maximum energy densities of 1150 mJ/kg and 2.23 mJ/mm³ for the corresponding IPT. / Ph. D.

Recent efforts toward the commercialization of hydrogen fuel cells, a sustainable energy technology, have led to interest in the effects of industrial processing parameters on the morphology and properties of fuel cell ionomers. The ionomer functions as a solid electrolyte membrane on the order of microns thick and as a thin film on the order of tens of nanometers in the catalyst layer. Industrial manufacture of the membrane and catalyst layer is typically a roll-to-roll process that involves casting a colloidal dispersion of the fuel cell ionomer in predominantly mixed alcohol/water solvent systems onto a backing film or substrate, followed by evaporation of the solvent and annealing of the ionomer at elevated temperatures. The current benchmark fuel cell ionomers are a class of polymers with pendant perfluorinated side chains terminating in sulfonic acid groups, called perflurosulfonic acid ionomers (PFSAs). The purpose of this dissertation is to investigate the effects of industrial processing parameters such as dispersion solvent composition, solvent evaporation temperature, and annealing temperature on fuel cell-relevant properties of PFSA solid electrolyte membranes and model thin films. Particular focus is given to newer-generation PFSAs and the effect of their different chemical structures on the morphology and properties of dispersions, membranes, and thin films. Dipole-dipole interactions between colloidal aggregates modulated by solvent composition were found to significantly influence the viscosity of PFSA dispersions. A framework of PFSA-solvent interactions is developed to predict the onset of dipole-dipole interactions as a function of PFSA chemical structure and solvent composition. Increased steric hindrance of shorter PFSA side chain chemical structures is found to inhibit morphological development, resulting in membranes with poorer wet and dry mechanical properties. A shorter side-chain PFSA is suggested to require higher processing temperatures to achieve performance equivalent to a PFSA with slightly longer side chain. The morphology and properties of model PFSA thin films are demonstrated to decay to quasi-equilibrium values upon physical aging at both low and high relative humidity (RH). Thin film swelling curves are demonstrated to be superposable by implementing an aging time-RH shift factor, allowing for prediction of quasi-equilibration times under given fuel cell operating conditions. / Doctor of Philosophy / Interest in environmentally friendly, sustainable energy sources has led to significant industrial, academic, and governmental efforts to commercialize hydrogen fuel cells. Hydrogen gas is split into protons and electrons in the anode catalyst layer. The electrons flow through an external circuit to produce electricity, while the protons are transported from the catalyst layer through a solid electrolyte membrane to the anode to react with oxygen to form water. A key component of hydrogen fuel cells is an ion-containing polymer called an ionomer that is required for the transport of (1) protons in the solid electrolyte membrane and (2) protons and reactant gases in the catalyst layer. The solid electrolyte membrane and catalyst layer can be industrially produced by a continuous process that involves dispersing the ionomer in a mixed alcohol/water solvent and coating it onto a backing film, followed by evaporation of the solvent and annealing of the ionomer. The present work is an investigation of the effect of industrially-relevant processing parameters on the morphology and properties of a class of ionomers called perfluorosulfonic acid ionomers (PFSAs), which phase separate into hydrophilic domains that serve as transport pathways and hydrophobic domains that impart thermomechanical stability. Practical aspects of the processing and function of PFSAs, including viscosity of the PFSA dispersion, minimum processing temperature to achieve solvent stability, and physical aging of the PFSA during fuel cell operation are shown to be fundamentally related to the PFSA chemical structure and morphology.

Water and ion transport critically determine the performance of many functional materials and devices, from fuel cells to lithium ion batteries to soft mechanical actuators. This dissertation aims to address some fundamental issues regarding transport and anisotropy, structural heterogeneity and molecular interactions inside ionic polymers. I first discuss a main deficiency of a standard protocol for calibrating high pulsed-field-gradient NMR. I show that high gradient calibration using low γ nuclei is not amenable to measurements on slow diffusing high γ nuclei. Then I employ NMR diffusometry to investigate transport and anisotropy for a series of ionic polymers, from poly(arylene ether sulfone) hydrophilic-hydrophobic multi-block copolymers to polymer blends to perfluorosulfonate random copolymers. For the multi-block copolymers, NMR diffusion measurements yield diffusion anisotropy as a function of water uptake and block lengths. ²H NMR spectroscopy on absorbed D₂O probes membrane alignment modes. These measurements also provide insights into average defect distributions. For the blend membranes, we examine the impact of compatibilizer on their transport properties. An increase in compatibilizer significantly improves the membrane phase homogeneity confirmed by SEM and transport studies. Theories of diffusion in porous media yield changes in domain size and tortuosity that correspond to drastic changes in local restrictions to water diffusion among different blend membranes. NMR relaxometry studies yield multi-component T₁ values, which further probe structural heterogeneities on smaller scales than diffusion experiments. For the random copolymer, the exploration of ion transport reveals inter-ionic associations of ionic liquids (ILs) modulated by hydration level and ionic medium. When ILs diffuse inside ionic polymers, isolated anions diffuse faster (≥ 4X) than cations at high hydration whereas ion associations result in substantially faster cation diffusion (≤ 3X) at low hydration inside membranes, revealing prevalent anionic aggregates. Finally, I present the strategy and analytical protocol for studying ionomer membranes using ILs. The normal cation diffusion contrasts to the anomalous anion diffusion caused by local confinement structures inside the membranes, which vary drastically with temperature and hydration level. These structures correspond to a density variation of SO₃⁻ groups, which define a distribution of local electrical potentials that fluctuate with temperature and nature of ionic media. / Ph. D.

Polymers containing less than 10 mol % of ions (ionomers) have been studied in depth for their potential in producing polymers with tailored properties for specific applications. A small molar percentage of ions can be incorporated into a polymer to drastically enhance the properties of the polymer. An ionomer that has been studied is that of isoprene copolymerized with sodium styrene sulfonate (poly(I-co-NaSS)). Research has been performed relating to the synthesis and chemical characterization of the copolymers. However, an in depth study of the way the physical properties are affected by a change in ion concentration has not been presented. Thus, it is the goal of this thesis to synthesize a series of poly(I-co-NaSS) copolymers with varying levels of sulfonated styrene and characterize their physical properties. The poly(I-co-NaSS) polymers, containing a range of 1.15 to 4.74 mol % NaSS, were polymerized using free radical emulsion polymerization. The copolymer compositions were confirmed using combustion sulfur analysis. Dynamic light scattering indicated that large aggregates were present in solution. These aggregates were large enough that capillary intrinsic viscosities could not be measured. Small angle x-ray scattering (SAXS) and thermal analysis showed little change as the ion concentration was increased, while tensile, stress relaxation and adhesion properties were improved. The absence of changes in the SAXS patterns indicated that there was an absence of a well-defined ionic aggregate, while the mechanical properties showed evidence of electrostatic interactions. This can be at least partially attributed to ionic interactions on a smaller scale (doublets, triplets). / Master of Science / This research pertains to the creation of a series of polymers containing small amounts of ionic groups that allow tailoring the properties of the materials. The main component of the polymer is polyisoprene, which is also referred to as “natural rubber”. This material is elastic and can be used as a rubber (gloves) or can be manipulated to create a strong adhesive through addition of ionic groups. The polymers were synthesized with varying levels of ionic groups, creating a series of six polymers. These polymers were tested for their chemical composition (the chemical make-up of the polymers), morphological properties (their phase structure and self-assembly of the polymers on a nanometer to micron scale), and their mechanical properties (the strength, elasticity, and adhesive properties of the polymer). It was determined that in terms of the morphology, the polymer remained mostly unchanged as the ion content was increased, but the mechanical properties improved dramatically. As the concentration of ionic groups increased, the strength of the polymer as well as the adhesive properties of the polymer, also increased. Understanding the structure-property relationships of these copolymers can allow researchers to tailor their structures to fit a desired application.

Recent advancements in supramolecular chemistry have given a wealth of strongly binding host-guest combinations. However, the deployment of these systems into meaningful constructs has been hindered due to difficulty of synthesis or to the lack of functionality in one or both components. Systems caught in this trap were the pyridyl cryptands of dibenzo-30-crown-10 and bis(m-phenylene)-32-crown-10 paired with paraquat. Exceptionally high association constants in the range of 105 to 106 have been observed for these systems, but their applications have been hindered. Easing the implementation of pyridyl cryptands based on dibenzo-30-crown-10 was made a priority. An efficient method for the synthesis of pyridyl cryptands based on dibenzo-30-crown-10 and bis(m-phenylene)-32-crown-10 made use of the salt pyridinium bis(trifluoromethane)sulfonamide (TFSI) as a template. Optimization of the pyridinium TFSI template allowed for cyclization yields as high as 89%, as well as without the use of a syringe pump. Addressing the concern of functionality, for pyridyl cryptands, chelidamic acid was targeted as a way to build in functionality. Using a chelidamic isopropyl ester, 20 new chelidamic precursors of varying functionality were synthesized. The chelidamic derivatives fell into six groups: potential covalent monomers, initiators, chain terminators, leaving groups, aryl halides and host-guest monomers. In an attempt to boost the association constants of pyridyl cryptands based on dibenzo-30-crown-10 with paraquat, alterations to the paraquat guest were explored. It was found that the association constants could be increased by nearly an order of magnitude. Tweaks to the paraquat included changing the counterion to TFSI, methyl groups to benzyl and allowing for access to more nonpolar solvents that were previously inaccessible, such as solvent change from DCM to acetone. Two new biscryptands and two new bisparaquat TFSI monomers were synthesized. Using these monomers supramolecular polymers were synthesized and characterized. Fibers of these polymers drawn from concentrated solutions were found to be flexible and one such polymer solution was found to have an upper log / log specific viscosity–concentration slope of 3.55, which is the theoretical maximum. Additionally, a biscryptand was used to produce a chain extended polymer. Using a fundamental understanding of host-guest chemistry, work was conducted on the synthesis of norbornene monomers and polymers with pendant imidazolium tethered by ethyleneoxy linkages to aid in the stabilization of the imidazolium cation. Through the use of ethyleneoxy linkages, the free anion content and conductivity was increased. Imidazolium monomer and polymer conductivities ranged up to nearly 10-4 S/cm. Furthermore, it was determined that as long as the ethyleneoxy spacer between the norbornene and imidazolium was two units or greater, similar properties were obtained for both the monomer and corresponding polymer. Expanding the work further, the imidazolium monomers were incorporated as a soft segment into a triblock copolymer to produce a single direction mechanical actuator. / Ph. D.

Indiana University-Purdue University Indianapolis (IUPUI) / Objectives: Repair of crown margins may extend the functional life of existing crowns. However, the longevity of such treatment is unknown. This study determined the survival time of crown margin repairs (CMR) with glass-ionomer (GI) and resin-modified glass-ionomer cements. Methods: We queried axiUm (Exan Group, Coquitlam, BC, Canada) database for permanent teeth that underwent CMR in the Graduate Operative Dentistry Clinic, Indiana University School of Dentistry (IUSD), Indianapolis, Ind., USA, from January 1, 2006 through January 1, 2018. Since there is no CDT code for the CMR procedure, CDT codes for resin-composite and GI restorations (D23XX) were queried; these patients also had treatment notes that indicated CMR. The final data set included patient ID, birth date, gender, dates of treatments, CDT codes, tooth type, tooth surface and existing findings. Two examiners developed guidelines for record review and manually reviewed the clinical notes of patient records to confirm CMR. Only records that were confirmed with the presence of CMR were retained in the final dataset for survival analysis. Survival time was calculated by Kaplan-Meier statistics and a Cox Proportional Hazards model was performed to assess the influence of selected variables (p < 0.05). Results: 214 teeth (115 patients) with CMR were evaluated. Patient average age was 69.4  11.7 years old. Posterior teeth accounted for 78.5 percent (n = 168) of teeth treated. CMRs using GI had a projected 5-year survival rate of 62.9 percent (K-M Analysis) and an 8.9 percent annual failure rate. Cox Proportional Hazards Regression analysis revealed that none of the factors examined (age, gender, tooth type) affected time to failure. Conclusion: CMRs may extend the longevity of crowns with defective margins. Larger EHR studies or case control studies are needed to investigate other variables, such as the caries risk status or the severity of defects that may affect the survival rate of CMRs.