Design of Polymeric Materials: Novel Functionalized Polymers for Enhanced Oil Recovery & Gas Sorption Applications

As material requirements for particular applications become more specific and strict, using a targeted approach to design polymeric materials becomes a necessity. Following a general design framework prevents researchers from using trial-and-error approaches or shoehorning materials into applications for which they are non-optimal. To obtain polymer products with desirable properties (both fundamental characteristics and for a specific application), one must always begin with an awareness of existing materials and methods. This background knowledge informs preliminary design of experiments, which in turn provides insight for additional experiments to synthesize (and characterize) optimally designed materials. A general framework for the design of polymeric materials has been developed in this thesis, and the specific aspects are grounded in two independent case studies. These two distinct (yet related) case studies have been selected to demonstrate that the framework is not limited to a particular industry or application, nor to a specific type of polymeric material. In Case Study #1, water-soluble terpolymers (and related polymerization kinetics) are investigated for use in polymer flooding during enhanced oil recovery (EOR). In contrast, Case Study #2 examines a variety of polymeric materials that have the potential to be used for acetone gas sensing (for diabetic applications). Both case studies use the same general design framework in a sequential, iterative manner to move towards optimally designed materials for each target application. Polymers are already used in EOR; the most common synthetic material used for polymer flooding is partially hydrolyzed polyacrylamide (HPAM). In many cases, polymers for EOR are exposed to high temperatures, high shear rates, and high concentrations of salt in the reservoir. The shortcomings of HPAM include poor thermal stability, poor shear stability, and poor brine compatibility. As a result, HPAM can degrade during EOR, thus lowering molecular weight averages and reducing oil recovery efficiency. Therefore, the target for Case Study #1 is to build on existing knowledge to improve acrylamide-based polymers for enhanced oil recovery. Important characteristics of polymeric materials for EOR include good viscosity modification (achieved through water solubility, high molecular weight averages and the incorporation of carboxylate ions), reasonable chemical stability (achieved by incorporating high levels of amide groups into the polymer), and a good distribution of ions along the polymer backbone (that is, a targeted sequence length distribution). HPAM (a copolymer of acrylamide (AAm) and acrylic acid (AAc)) meets these requirements, but the thermal and shear stability concerns described above have not been considered. Therefore, a third comonomer, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) can be added to the polymer formulation, as the bulky sulfonic acid groups are expected to improve thermal stability and protect the main chain from shear degradation. When a multi-component polymer like AMPS/AAm/AAc is being considered for any application, understanding and manipulating ternary reactivity ratios (which are related to both the cumulative terpolymer composition and the sequence length distribution) is essential. Therefore, once the AMPS/AAm/AAc terpolymer is selected for enhanced oil recovery, relationships between (experimental) synthesis conditions and polymer properties can be researched, verified and exploited. First, a comprehensive study (involving both an examination of the literature and a series of designed screening experiments) is performed to establish the effect of synthesis conditions (like pH, ionic strength, monomer concentration and feed composition) on the terpolymerization kinetics and product terpolymer properties. Deliberate design of screening experiments (designed considering the ‘rule-of-thumb’ for ternary reactivity ratio estimation) makes it possible to establish that the key factors within the experimental range studied are ionic strength (which affects cumulative terpolymer composition and sequence length distribution), monomer concentration (which affects molecular weight averages) and feed composition (which, of course, impacts the cumulative composition of the terpolymer product). Given the results of the screening experiments, two optimal terpolymers of AMPS/AAm/AAc are designed, synthesized, characterized and tested. The designed terpolymers have polymer properties that agree with model predictions, but (more importantly) show excellent EOR performance. In a series of sand-pack flooding experiments (simulating enhanced oil recovery in a reservoir), the designed terpolymers perform much better than reference materials. The newly synthesized terpolymers achieve an overall oil recovery of (on average) 78.0% for one optimal material and 88.7% for the second optimal material. In contrast, the commercially available reference material allows for an overall oil recovery of 59.8%. Therefore, the design framework has allowed us to converge upon optimal terpolymer formulations with excellent EOR application performance. The same general framework is applied to inform the design, synthesis and characterization of polymeric sensing materials for acetone detection. Highly concentrated breath acetone measurements are correlated with high levels of blood glucose, so detecting acetone gas could be useful in a non-invasive breath sensor for diabetic applications. In this case, key design considerations (to inform potential backbone selection) include operational temperature (and the glass transition temperature of candidate polymeric materials), surface morphology, and the chemical behaviour of the target analyte. Solubility parameters, for example, can be used to provide insight about the compatibility of the target analyte (acetone) and potential sensing materials. For polymeric sensing materials, the most important characteristics are sensitivity and selectivity. Sensitivity studies provide information about how well the target analyte sorbs onto the polymeric material (that is, whether there is a strong affinity towards acetone), and selectivity measures how well the target analyte sorbs in the presence of other interferent gases. After preliminary screening (based on a detailed literature review), three polymer backbones and three metal oxide dopants are selected as promising candidates for acetone sensing. Polyaniline, polypyrrole and poly(methyl methacrylate) are doped with varying quantities of SnO2, WO3 and ZnO nanoparticles. In a series of screening experiments, 30 materials are synthesized and evaluated in terms of acetone sorption (using a uniquely designed gas sensing set-up and a highly specialized gas chromatograph). The most promising materials are evaluated further, both in terms of surface morphology and in terms of selectivity (measurement of acetone sorption in the presence of acetaldehyde, ethanol and benzene). In general, pure polyaniline and pure polypyrrole show the most promise of the materials studied; poly(methyl methacrylate) does not sorb acetone at all, and metal oxide doping (using these dopants and up to 20 wt% doping) does not improve application performance. In the customized experiments, adjustments are made to polymer synthesis steps in an attempt to improve the properties of the polymeric sensing materials (especially in terms of selectivity). One customization option that is investigated is the acid-doping of polyaniline (synthesis in an aqueous oxalic acid solution) to change the backbone charge, thereby taking advantage of the polarity of acetone. Another customization option involves the synthesis of copolymers of polyaniline and polypyrrole (both in water and in oxalic acid solution) by combining the two monomers in a single formulation. Product characterization shows some improvement over the original (screening) materials, but further improvement is still possible. Therefore, this target application can continue to benefit from sequential, iterative steps towards optimality. Ultimately, both case studies overlap when the general design framework is considered. An awareness of existing materials and methods can inform statistically designed preliminary experiments, which eventually lead to optimally designed materials for specific (targeted) applications. The contents of this thesis (especially the two major case studies) and several related publications demonstrate that this framework is useful and relevant for design of polymeric materials. The effectiveness is visible throughout the research process, but it is especially evident in the application performance of the final (optimal) product, along with the flexibility of the design approach with respect to expanding into new areas, at the same time by minimizing time and effort

Effect of solution properties on the terpolymerization of 2-acrylamido-2- methylpropane sulfonic acid, acrylamide and acrylic acid

The water-soluble terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm) and acrylic acid (AAc) is an interesting and largely unstudied system. This new terpolymer has only recently appeared in the literature, with applications ranging from enhanced oil recovery [1] to controlled drug delivery [2]. Typically, existing studies focus on the final properties of the material (swelling behavior, thermal and mechanical stability, etc.), but investigating the terpolymerization kinetics is equally important [3]. The bulk polymer properties (and, by extension, properties relevant to the final application) depend on the terpolymer microstructure, therefore a clear understanding of the terpolymerization kinetics is invaluable. Please download the file below for full content

Nocturnal pollination: An overlooked ecosystem service vulnerable to environmental change

© 2020 The Author(s). This is an open access article published by Portland Press Limited on behalf of the Biochemical Society and the Royal Society of Biology and distributed under the Creative Commons Attribution License 4.0 (CC BY). Existing assessments of the ecosystem service of pollination have been largely restricted to diurnal insects, with a particular focus on generalist foragers such as wild and honey bees. As knowledge of how these plant-pollinator systems function, their relevance to food security and biodiversity, and the fragility of these mutually beneficial interactions increases, attention is diverting to other, less well-studied pollinator groups. One such group are those that forage at night. In this review, we document evidence that nocturnal species are providers of pollination services (including pollination of economically valuable and culturally important crops, as well as wild plants of conservation concern), but highlight how little is known about the scale of such services. We discuss the primary mechanisms involved in night-time communication between plants and insect pollen-vectors, including floral scent, visual cues (and associated specialized visual systems), and thermogenic sensitivity (associated with thermogenic flowers). We highlight that these mechanisms are vulnerable to direct and indirect disruption by a range of anthropogenic drivers of environmental change, including air and soil pollution, artificial light at night, and climate change. Lastly, we highlight a number of directions for future research that will be important if nocturnal pollination services are to be fully understood and ultimately conserved

Negative emotional reactivity as a marker of vulnerability in the development of borderline personality disorder symptoms

Negative emotionality is a distinguishing feature of borderline personality disorder (BPD). However, this person-level characteristic has not been examined as a marker of vulnerability in the development of this disorder. The current study utilized a multi-method approach to examine the interplay between negative emotional reactivity and cumulative exposure to family adversity on the development of BPD symptoms across three years (ages 16–18) in a diverse, at-risk sample of adolescent girls (N=113). A latent variable of negative emotional reactivity was created from multiple assessments at age 16: (1) self-report, (2) emotion ratings to stressors from ecological assessments across one week, and (3) observer-rated negative affectivity during a mother-daughter conflict discussion task. Exposure to family adversity was measured cumulatively between ages 5 and 16 from annual assessments of family poverty, single parent household, and difficult life circumstances. Results from latent growth curve models demonstrated a significant interaction between negative emotional reactivity and family adversity, such that exposure to adversity strengthened the association between negative emotional reactivity and BPD symptoms. Additionally, family adversity predicted increasing BPD symptoms during late adolescence. These findings highlight negative emotional reactivity as a marker of vulnerability that ultimately increases risk for the development of BPD symptoms

The Maluridae: Inferring Avian Biology and Evolutionary History from DNA Sequences

The Australo-Papuan fairy-wrens, emu-wrens and grasswrens comprise the passerine family Maluridae. They have long been known for their spectacular plumages, remarkable behavioural ecology and intriguing biogeography. The family has provided an ideal model with which to explore how phylogenetic and phylogeographic analyses of DNA-sequence data can inform understanding of evolutionary history and present-day biology. We review what has been learned of the phylogeny of the group and the phylogeographic history of individual species. We conclude that there is now a strong framework within which to pursue the remaining species-level taxonomic issues, and to extend ecological and behavioural studies into a new era of more detailed genetic questions such as the role of gene–environment interactions in adaptation. We highlight some remaining examples of such questions and discuss how they might be addressed.Organismic and Evolutionary Biolog

Investigation of Reactivity Ratios for the AMPS/AAm/AAc Terpolymer and Associated Copolymers

Water-soluble polymers of acrylamide (AAm) and acrylic acid (AAc) have significant potential in enhanced oil recovery, as well as in other specialty applications. However, to improve the shear strength of the polymer, it may be beneficial to add a third comonomer to the pre-polymerization mixture. Homopolymerization kinetics of acrylamide and acrylic acid have been studied previously, as have the copolymerization kinetics of these two comonomers. Therefore, in the current study, the kinetics of three additional systems are investigated: copolymerization of AMPS/AAm and AMPS/AAc and terpolymerization of AMPS/AAm/AAc. Copolymerization experiments for both AMPS/AAm and AMPS/AAc were designed using two optimal techniques (Tidwell-Mortimer and the error-in-variables-model (EVM)) and terpolymerization experiments for AMPS/AAm/AAc were optimally designed using EVM. From these optimally designed experiments, accurate reactivity ratio estimates were determined for AMPS/AAm, AMPS/AAc and AMPS/AAm/AAc. To better understand the error associated with each system, reactivity ratio point estimates for both the binary and ternary systems were presented using joint confidence regions (JCRs). The estimates were evaluated by comparing model predictions to experimental data, and the effect of experimental error was studied using sensitivity analyses. Finally, a direct comparison of binary and ternary reactivity ratios (for similar systems under the same experimental conditions) was possible for the first time

Impaction of spray droplets on leaves: influence of formulation and leaf character on shatter, bounce and adhesion

This paper combines experimental data with simple mathematical models to investigate the influence of spray formulation type and leaf character (wettability) on shatter, bounce and adhesion of droplets impacting with cotton, rice and wheat leaves. Impaction criteria that allow for different angles of the leaf surface and the droplet impact trajectory are presented; their predictions are based on whether combinations of droplet size and velocity lie above or below bounce and shatter boundaries. In the experimental component, real leaves are used, with all their inherent natural variability. Further, commercial agricultural spray nozzles are employed, resulting in a range of droplet characteristics. Given this natural variability, there is broad agreement between the data and predictions. As predicted, the shatter of droplets was found to increase as droplet size and velocity increased, and the surface became harder to wet. Bouncing of droplets occurred most frequently on hard to wet surfaces with high surface tension mixtures. On the other hand, a number of small droplets with low impact velocity were observed to bounce when predicted to lie well within the adhering regime. We believe this discrepancy between the predictions and experimental data could be due to air layer effects that were not taken into account in the current bounce equations. Other discrepancies between experiment and theory are thought to be due to the current assumption of a dry impact surface, whereas, in practice, the leaf surfaces became increasingly covered with fluid throughout the spray test runs.Comment: 19 pages, 6 figures, accepted for publication by Experiments in Fluid

Management Forecasts, Analyst Revisions, and Investor Reactions: The Effect of CEO Gender

In this study, we examine whether CEO gender affects the likelihood of management forecast issuance, forecast properties, and subsequent reactions from analysts and investors. We use a panel data set of CEO transitions between 2000 and 2015 to test our hypotheses. We find that while women CEOs are more likely to issue earnings forecasts after a CEO transition, the characteristics of forecasts issued by women and men CEOs do not differ. Furthermore, we find that CEO gender significantly affects analyst and investor reactions. In particular, we find that analysts and investors demonstrate a more tempered reaction to good news forecasts issued by women CEOs compared to men CEOs. Overall, our findings suggest that analysts and investors find management forecasts issued by women CEOs to be less credible than forecasts issued by men CEOs despite no apparent differences in their forecast properties