A primary concern in the geologic storage of anthropogenic carbon dioxide is the leakage of buoyant CO₂ plumes into shallower formations, aquifers, or the surface. Man-made wells drilled through these formations present a potential leakage pathway for this CO₂ as the cement binding the well to the earth develops fractures or debonded microannuli form over time. Typically, wells with poor cementing or suspected leaks are subject to a cement-squeeze, in which new cement is injected to eliminate the leakage pathway. However, small fractures or leakage pathways are often difficult for oilfield cement to repair, as the cement dispersion is potentially screened out from dispersing fluid and cannot enter the fracture. Therefore a low-viscosity sealant is desired that can enter these leakage pathways easily and provide a robust seal. A class of poly(acrylic acid) polymers known commercially as Carbopol® are pH-sensitive microgels and swell/thicken upon neutralization with alkali cement components. These polymer dispersions are tested for ease of placement into cement fractures and subsequent development of resistance to displacement. Laboratory experiments involved injecting various unswollen polymer microgel dispersion into constructed cement fractures while measuring injection pressure and the pH of the polymer effluent to quantify the chemical reactions taking place and the induced viscosity changes. Fractures were constructed in order to allow for visual inspection of the polymer microgel swelling during and after injection, qualitatively useful in determining the polymer’s efficiency at blocking cement fractures. It was determined that polymer microgels undergo syneresis in the presence of calcium cations that are dissolved from minerals present in cement. The syneresis causes the polymer to collapse onto the cement fracture face and expelled water is left to fill the rest of the fracture, providing little to no resistance to subsequent flow. However, the syneresed polymer does show some potential in blocking or partially blocking small aperture fractures and is not entirely detrimental to fracture blockage in small amounts. An acid pre-flush prior to polymer injection has been seen to favorably reduce the amount of calcium and therefore extent of syneresis, allowing swollen polymer microgels to remain intact and block fluid flow. / text

Synthetic polymers intended for use in biomedical applications require the additional criteria of biocompatibility and sometimes biodegradability included within the design parameters along with mechanical properties, manufacturability, and other properties depending on the specific application in mind. The composition of the monomer and the type of linker within the main chain polymer as well as the chemical reactivity of these chemical entities will define the degradation rates and the conditions under which degradation will or will not occur. However, biocompatibility is usually a built-in characteristic related to the polymer (and monomer) composition and is not easily engineered into an existing polymer by conversion from a non-biocompatible to a biocompatible polymer. Consequently, a majority of the biocompatible polymers used in medical devices or evaluated for biomedical uses are composed of substances that are natural metabolites or known to be biocompatible and nontoxic. Using this design principle, a number of successful examples of biocompatible polymers have been reported such as poly(lactic acid), poly(glycolic acid), and their copolymers, and today, all of these polymers are used in US and EU approved devices. For similar reasons, glycerol-based polymers are attracting increasingly more attention for both fundamental studies and practical applications. Various glycerol polymer architectures from linear to dendritic have been reported for pure polyglycerol ethers and carbonates as well as copolymers with hydroxyacids, for example, to give polyether esters or polycarbonate esters. Herein, the design and synthesis of glycerol-based polycarbonates via copolymerization of epoxide and carbon dioxide is described. The underlying chemistry that affords these glycerol-based polycarbonates will be discussed. Their structural characteristics, their chemical, physical, and rheological properties, and as well as their applications with a focus on drug carrier will also be covered.

A co-polymer made from Polyvinyl Alcohol and Polyacrylic Acid (PVA-PAA) has been synthesized to form new robotic actuation systems which use the contractile and variable compliance properties of this material. The stimulation of these fibres is studied (particularly chemical activation using acetone and water), as are the factors which influence the response, especially those relating to its performance as an artificial muscle. Mathematical models and simulations of the dynamics of the polymeric strips have been developed, permitting a thorough analysis of the performance determining parameters. Using these models a control strategy has been designed and implemented, with experimental results being obtained for a gripper powered by a flexor/extensor pair formed using these polymeric actuators. An investigation of a second property of the polymer, its variable compliance is alsoincluded. Use of this feature has lead to the design, construction and testing of a multi degree-of-freedom dextrous hand, which despite having only a single actuator, can exercise independent control over each joint.

Nanosized metal particles have become an important class of materials in the field of catalysis, optical, electronic, magnetic and biological devices due to the unique physical and chemical properties. This research deals with the synthesis of structured bimetallic nanoparticles for the dechlorination of toxic organics. Nanoparticle synthesis in aqueous phase for dechlorination studies has been reported. However, in the absence of polymers or surfactants particles can easily aggregate into large particles with wide size distribution. In this study, we report a novel in-situ synthesis method of bimetallic nanoparticles embedded in polyacrylic acid (PAA) functionalized microfiltration membranes by chemical reduction of metal ions bound to the carboxylic acid groups. Membrane-based nanoparticle synthesis offers many advantages: reduction of particle loss, prevention of particle agglomeration, application of convective flow, and recapture of dissolved metal ions. The objective of this research is to synthesize and characterize nanostructured bimetallic particles in membranes, understand and quantify the catalytic hydrodechlorination mechanism, and develop a membrane reactor model to predict and simulate reactions under various conditions. In this study, the PAA functionalization was achieved by filling the porous PVDF membranes with acrylic acid and subsequent in-situ free radical polymerization. Target metal cations (iron in this case) were then introduced into the membranes by ion exchange process. Subsequent reduction resulted in the formation of metal nanoparticles (around 30 nm). Bimetallic nanoparticles can be formed by post deposition of secondary appropriate metal such as Pd or Ni. The membranes and bimetallic nanoparticles were characterized by: SEM, TEM, TGA, and FTIR. A specimen-drift-free X-ray energy dispersive spectroscopy (EDS) mapping system was used to determine the two-dimensional element distribution inside the membrane matrix at the nano scale. This high resolution mapping allows for the correlation and understanding the nanoparticle structure, second metal composition in terms of nanoparticle reactivity. Chlorinated aliphatics such as trichloroethylene and conjugated aromatics such as polychlorinated biphenyls (PCBs) were chosen as the model compounds to investigate the catalytic properties of bimetallic nanoparticles and the reaction mechanism and kinetics. Effects of second metal coating, particle size and structure and temperature were studied on the performance of bimetallic system. In order to predict reaction at different conditions, a two-dimensional steady state model was developed to correlate and simulate mass transfer and reaction in the membrane pores under convective flow mode. The 2-D equations were solved by COMSOL (Femlab). The influence of changing parameters such as reactor geometry (i.e. membrane pore size) and Pd coating composition were evaluated by the model and compared well with the experimental data.

No description available.

Conventional glass ionomer cements (GICs), which continue to gain acceptance as superbly biocompatible dental materials, were first released in the early 1970s as a result of research into combining the advantages of silicate cements and polyalkenate cements. The chemistry of GICs is based upon the aqueous reaction between an ion-leachable fluoride glass and polyacid which yields the final cross-linked insoluble ionomer (ionic polymer). The significant advantages of GICs include direct adhesion to tooth structures, fluoride release, minimal dimensional change on curing, significant ease of use and superb biocompatibility, to the extent that affected proximal tooth structures may be retained, remineralised , and strengthened against further caries. GICs have, however, been unfavourably compared with other restorative materials in their mechanical properties and setting characteristics, in particular their relative weakness, the time limitations for the acid-base reaction to proceed to acceptable maturity, and the susceptibility of the immature cement to water sorption or desiccation.

Conventional glass ionomer cements (GICs), which continue to gain acceptance as superbly biocompatible dental materials, were first released in the early 1970s as a result of research into combining the advantages of silicate cements and polyalkenate cements. The chemistry of GICs is based upon the aqueous reaction between an ion-leachable fluoride glass and polyacid which yields the final cross-linked insoluble ionomer (ionic polymer). The significant advantages of GICs include direct adhesion to tooth structures, fluoride release, minimal dimensional change on curing, significant ease of use and superb biocompatibility, to the extent that affected proximal tooth structures may be retained, remineralised , and strengthened against further caries. GICs have, however, been unfavourably compared with other restorative materials in their mechanical properties and setting characteristics, in particular their relative weakness, the time limitations for the acid-base reaction to proceed to acceptable maturity, and the susceptibility of the immature cement to water sorption or desiccation.

The application of Cerium oxide nanoparticles (CNPs) for therapeutic purposes requires a stable dispersion of nanoparticles in biological environment. The objective of this study is to tailor the properties of polyelectrolyte coated CNPs as a function of molecular weight to achieve a stable and catalytic active dispersion. This was achieved by coating CNPs with polyacrylic acid (PAA) which increased the dispersion stability of CNPs and enhanced the catalytic ability. The stability of PAA coating was analysed using the change in the Gibbs free energy computed by Langmuir adsorption model. The adsorption isotherms were determined using soft particle electrokinetics which overcomes the challenges presented by other techniques. The Gibbs free energy was highest for PAA coated CNPs by 250 kg/mole indicating the most stable coating. The free energy for PAA 100 kg/mole coated CNPs is 85% lower than the PAA250 coated CNPs. This significant difference is caused by the strong adsorption of PAA100 on CNPs. Catalytic activity of PAA-CNPs is accessed by the catalase enzymatic activity of nanoparticles. The catalase activity was higher for PAA coated CNPs as compared to bare CNPs which indicated preferential adsorption of hydrogen peroxide induced by coating. Apart from PAA coating the catalase activity is also affected by the structure of the coating layer.

The antioxidant activity of novel drugs has been of increasing interest in recent years. Free radicals are linked as a cause to many diseases such as atherosclerosis and cancer,1 so development of drugs that can scavenge and break down free radicals is needed. One such potential solution is using dopamine, which is water-soluble and an antioxidant. However, the tendency of antioxidant drugs reacting undesirably with proteins and other biochemical compounds is a big issue for the drugs' antioxidant potential. One solution is by encapsulating the antioxidant compound in biocompatible polymer nanoparticles. In this project, dopamine is bound to the polymer polyacrylic acid (PAA) and spherical PAA-dopamine nanoparticles were synthesized. Following their synthesis, the nanoparticles were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscope (TEM), and Fourier-Transform Infrared (FT-IR) spectroscopy and were shown to have an average size of 90 nm after dialysis cleaning. Finally, their hydroxyl radical (OH·) scavenging ability was tested through pH changes and fluorescence, and the data acquired suggests possible radical scavenging potential.

Aircraft are not allowed to take off prior to cleaning of snow and ice deposits that form on their surfaces under winter conditions to refrain from compromising flight safety. Water based solutions containing mainly ethylene or propylene glycol, or both, are employed either to remove the snow/ice layers or to provide protection against deposition of these layers. The first group of solutions, i.e. de-icing fluids, are Newtonian and have generally low viscosity so that right after their application they fall off the aircraft surfaces, providing little or no further protection against precipitation. Therefore, various anti-icing solutions have then been developed to provide the prolonged protection due to their non-Newtonian and high viscosity characteristics. Although the appropriate ranges of viscosity and surface tension have been determined in a number of studies, actual compositions of these solutions are proprietary. The main objective of this study is to determine the basic interactions between the chemical species in de/anti-icing fluids and their effects on the physical properties of the solutions, especially viscosity, surface tension,freezing point and corrosive effect which enable the design of the de/anti icing fluid composition. A number of polymers and surfactants were dissolved in water-glycol solutions and used in different compositions to get the desired viscosity and surface properties. The dependence of viscosity on polymer concentration, pH of the solutions, glycol content, surfactant concentration, temperature and shear rate were investigated and reported in detail. Among various chemicals, slightly crosslinked and hydrophobically modified polyacrylic acid was utilized as a thickener, sodium oleate and tributyl amine were used as surface agents in the de/anti-icing solutions whose physical properties satisfied the desired requirements. In addition to the studies about de/anti icing solutions, synthesis of a new polymer namely poly (DADMAC-co-vinyl pyyrolidone) was made and its characterization and performance tests were performed. High swelling ratios (up to 360) were attained with 0.5 % crosslinker in 2-3 minutes. Moreover, swellings of the gels were demonstrated to be independent of pH. It was also thought that such a copolymer having anti-bacterial effect induced by DADMAC (Diallyldimethyl ammonium chloride) segments and biocompatability of NVP (N-vinyl pyyrolidone) component would be of interest in biorelated areas.