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There is an increasing demand for robotics systems in production, inspection, and maintenance in the energy industry from offshore to onshore, to reduce operating costs and lower the risk of exposing humans to hazardous environments. However, a gap exists between existing workforce expertise and technologies that are developing rapidly. The deployment of robots requires the engineer to have rich experience in production and sufficient understanding of the robotic multidisciplinary system so they can identify and deploy the robot in the use case that can maximize the robot's efficiency. The nature of robotics and automation presents a challenge to the workforce since the existing workforce's background, in specific engineering disciplines or business, hinders them from adapting and then keeping up with the transition to robotic (not normally manned) operations. Directed by the University of Houston, the Subsea Systems Institute (SSI) is developing, in collaboration with Sprint Robotics, the National Robotarium (UK) and the Society of Underwater Technology (SUT), a robotic training program. The objective is to upskill and reskill the energy industry personnel (offshore and onshore) to meet the emerging industry demand for multidisciplinary robotics expertise. This group is collaborating to fill the gap between required knowledge and application in the energy industry by identifying the necessary knowledge and skillsets, and then developing an adaptable modular program with use cases to train the existing workforce. The SSI led effort will adjust to the differing needs that drive the adoption of this evolving technology, including engineers and scientists and other stakeholders such as managers, influencers, and the public.

Over the last 50 years, nuclear energy has reduced US energy-related CO2 emissions by over 30 gigatons compared to if the same electricity were produced by fossil fuels such as coal and natural gas. However, many kilotons of spent nuclear fuel have accumulated at different sites across the country, and sociopolitical factors have frustrated efforts to address the challenge of nuclear waste disposal. Presently, a consolidated interim storage facility in Andrews, Texas, provides a promising temporary solution. In this paper, we compare the technical and policy risks of the project to continued storage at independent spent fuel storage installations. Our results indicate that the cost of the radiological risk is low (

Summary Undetected gas kicks are at the root of many disastrous accidents in the oil industry. A major factor in these tragic outcomes is the suddenness with which oil and gas can be ejected from the top of the riser, which gives operators virtually no time for an adequate response. This aspect of the phenomenon is quantified by providing a physical explanation of its origin and suggesting simple, if approximate, guidelines to estimate its severity. Then a relatively straightforward and potentially practical way to detect the presence of dangerous gas volumes in a riser is described. The basic idea is to measure the pressure difference between sensors spaced along the riser. When gas occupies the space between sensors, the pressure difference undergoes large changes chiefly caused by the decreased hydrostatic head. It is shown that this difference can be enhanced by adequate signal processing and is robust in the presence of noise. The suggested detection method is supported by a set of laboratory experiments.

The mobility of polystyrene nanoparticles ranging in diameter from 300 nm to 2 μm was measured in dilute and semidilute solutions of partially hydrolyzed polyacrylamide. In this model system, the ratio of particle to polymer size controls the long-time diffusivity of nanoparticles. The particle dynamics transition from subdiffusive on short time scales to Fickian on long time scales, qualitatively similar to predictions for polymer dynamics using a Rouse model. The diffusivities extracted from the long-time Fickian regime, however, are larger than those predicted by the Stokes-Einstein equation and the bulk zero-shear viscosity and moreover do not collapse according to hydrodynamic models. The size-dependent deviations of the long-time particle diffusivities derive instead from the coupling between the dynamics of the particle and the polymer over the length scale of the particle. Although the long-time diffusivities collapse according to predictions, deviations of the short-time scaling exponents and the crossover time between subdiffusive and Fickian dynamics indicate that the particles are only partially coupled to the relaxation modes of the polymer.

Grafting of high molecular weight polymers to graphitic nanoplatelets is a critical step toward the development of high performance graphene nanocomposites. However, designing such a grafting route has remained a major impediment. Herein, we report a “grafting to” synthetic pathway by which high molecular weight polymer, poly(e-caprolactone) (PCL), is tethered, at high grafting density, to highly anisotropic graphitic nanoplatelets. The efficacy of this tethering route and the resultant structural arrangements within the composite are confirmed by neutron and X-ray scattering measurements in the melt and solution phase. In the semicrystalline state, X-ray analysis indicates that chain tethering onto the graphitic nanoplatelets results in conformational changes of the polymer chains, which enhance the nucleation process and aid formation of PCL crystallites. This is corroborated by the superior thermal properties of the composite, manifested in accelerated crystallization kinetics and a significant increas...

Particle-polymer attractions in nanocomposites can cause significant heterogeneities in the polymer dynamics and remarkably impact the material properties. Dynamical perturbations are generally expected to be limited to interfacial polymer segments. However, composites with highly anisotropic nanoparticles usually exhibit very low percolation thresholds. In such systems, the overlapping interfacial regions could result in a complex polymer relaxation behavior that is unanticipated from dilute nanoparticle dispersions in polymer matrices. To understand this behavior, we examine a system of percolated single-wall carbon nanotubes (SWNT) in a polymer matrix, PMMA, which is known to have strong interfacial binding. Neutron spectroscopy measurements on the composites reveal not only an interfacial polymer layer that is transiently pinned to the SWNT surface, but suggest that the percolated network forms a kinetic cage that dramatically restricts both local and cooperative relaxations of noninterfacial polymer segments. These findings should help guide theories and simulations of hierarchical polymer dynamics in nanocomposites.

The direct capture of CO2 from ambient air presents a means of decelerating the growth of global atmospheric CO2 concentrations. Considerations relating to process engineering are the focus of this review and have received significantly less attention than those relating to the design of materials for direct air capture (DAC). We summarize minimum thermodynamic energy requirements, second law efficiencies, major unit operations and associated energy requirements, capital and operating expenses, and potential alternative process designs. We also highlight process designs applied toward more concentrated sources of CO2 that, if extended to lower concentrations, could help move DAC units closer to more economical continuous operation. Addressing shortcomings highlighted here could aid in the design of improved DAC processes that overcome trade-offs between capture performance and DAC cost.

Rising anthropogenic CO2 emissions and global temperatures are a technological, social, and political challenge. These necessitate deep decarbonization through carbon management strategies for sust...

Thermodynamic interactions in binary blends of a copolymer containing diene and olefin repeat units and a polyolefin were explored, through measurements of the effective binary Flory–Huggins intera...

Two matrix-free polystyrene-grafted silica nanocomposite samples with graft chain lengths of 35 and 112 kg/mol are characterized by calorimetry and rheometry, and results are compared to neat polys...

The upstream oil and gas industry's digital transformation over the last few years has accelerated because of the COVID-19 pandemic. Data analytics and machine learning are key components of this digital transformation and have become essential skills for experienced petrotechnical professionals (PTPs) and aspiring entrants into the field. The objective of our work was to design and deliver a practical, engaging, and online microcredential certification program in upstream energy data analytics for PTPs. The program was conceived as a collaboration between academia (University of Houston's UH Energy) and industry (NExT, a Schlumberger company). It was designed as three belt levels (Bronze, Silver, and Gold), each containing three stackable badges of 12 to 15 hours duration per badge. Key design points included Identifying an online platform for administration Delivering convenient, interactive, live online sessions Delivering hybrid classes blending lectures and hands-on laboratories Designing laboratories using upstream datasets across various stages of oilfield expertise Administering test and quizzes, Kaggle competitions, and team projects. The program contents were designed incorporating appropriate instructional design practices for effective online class delivery. The design and delivery of the laboratories using a code-free approach by leveraging visual programming offers PTPs and new entrants a unique opportunity to learn data analytics concepts without the traditional concern of learning to code. Additionally, the collaboration between academia and industry enables delivering a program that combines academic rigor with application of the skills and knowledge to solve problems facing the industry using the real-world datasets. As a pilot program, all three badges of the Bronze belt were scheduled and successfully delivered during July and August 2020, as six 2-hour sessions per badge. From a total of 26 students registered in badge 1, 24 completed it, resulting in a completion rate of 92%. Out of these students, 19 registered and completed badge 2 and badge 3, resulting in the completion rates of 100%. Based on the success of the pilot program, a second delivery of the Bronze belt with 18 participants was offered from October 2020 through January 2021. All 18 participants completed all three badges. Feedback from participants attests to the success of the pilot program as seen in the following excerpts: "A very good course and instructors. I have already recommended the course to a friend and I will continue to be an advocate for the course." "Teachers are very receptive to questions and it is a joy to hear their lectures." "I found the University of Houston course to be both highly engaging and incredibly informative. The course teaches basic principles of data science without being bogged down by the specific coding language."

The work described here originated from the tragic and ultimately environmentally catastrophic event at the Macondo well in April 2010. The first part of the paper addresses the causes for the sudden and often destructive ejection of hydrocarbons from a riser when a gas kick escapes timely detection. The approach differs from previous work on the subject and provides a realistic understanding of the sequence of events responsible for the phenomenon. The focus is on the crucial few minutes and seconds prior to the sudden eruption of gas and provides a quantitative illustration of the extreme rapidity of the ejection which leaves no time for a drill crew to adopt mitigation measures. It is shown that, in many cases, a back-pressure applied at the top of the well can be beneficial. The second part of the paper describes a novel method for the detection of gas which relies on the measurement of pressure differences along sections of the riser. These data are sensitive to the mean density of the fluid in the section and can therefore detect the presence of free gas. Laboratory experiments supporting the idea are described. Proper signal processing can be developed which may be able to allow for automatic mitigation measures to be taken in the event of an otherwise undetected gas influx approaching the surface.

Blends of thermoset polymers offer an avenue to combine the mechanical properties of complementary high glass transition temperature systems. An epoxy resin with high tensile strength and modulus, composed of the diglycidyl ether of bisphenol A cured with an anhydride, was combined with polydicyclopentadiene, cured via ring-opening metathesis polymerization, to improve the toughness. An amphiphilic block copolymer, poly(1,4-butadiene-b-ethylene oxide), where 1,4-polybutadiene has a strong affinity for polydicyclopentadiene and poly(ethylene oxide) has a strong affinity for the epoxy resin, was added to control phase separation and manipulate the morphology of the thermoset blend, analogous to compatibilization in thermoplastic blends. A systematic study of the influence of block copolymer loading and blend composition on the structural morphology was performed, using a combination of ultrasmall-angle X-ray scattering (USAXS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM)....

The morphology of a block copolymer of a near symmetric strongly-segregating poly(n-butyl acrylate) and poly(methyl methacrylate) tethered to a ∼15 nm silica nanoparticles is examined using a combination of microscopy techniques and small angle x-ray and neutron scattering. The copolymer components are strongly segregated and form a disordered structure that is possibly a combination of coexisting individual randomly placed core-shell structures and worm-like cylinders with 3–5 silica nanoparticles forming the core. With increasing temperature, the cylinders become shorter because of the improved thermodynamic compatibility between the two copolymer segments.

Economic crises, such as the one induced by the COVID-19 pandemic, and resulting widespread corporate cost-cutting, drastically alter the nature of work. Job insecurity represents a critical intermediate between the economic ramifications of an economic crisis and work and stress outcomes, however, the underlying cognitive consequences of job insecurity and how to buffer those effects are not well understood. We examine how corporate cost-cutting announcements indirectly relate to employees’ attention through their relationship with employee job insecurity and investigate supervisor support as a potential buffer of these relationships. We used multi-source data to test our research model, combining data on cost-cutting announcements (budget cuts, layoffs, and furloughs) in news articles for 165 organizations with survey data from 421 full-time employees from these organizations between March 26, 2020 and April 8, 2020. Cost-cutting announcements are positively related to job insecurity, which is related to employee’s attention with supervisor support mitigating the effects of job insecurity on attention. Grounded in self-regulation theories, we contribute to and extend the theoretical understanding of the organizational context for job insecurity and cognitive outcomes. We discuss the implications for organizations to manage and prepare for future economic crises, specifically on organizational communication and supervisor interventions.

We study employee perspectives on return to physical workspaces to ultimately inform employers' and policy makers' decision making around the return to work during COVID-19.We tested the three-component conceptual model using survey data collected in the United States in May 2020 from samples of energy workers (N = 333).Women, non-Caucasians, and employees living in multi-generational households were less willing to return. Concerns about childcare were negatively related to willingness to return, whereas organizational strategies for mitigating COVID-19 transmission at work were positively related to willingness to return. COVID-19 infections in an employees' network were also negatively related to employees' willingness to return.Blanket policies may miss the nuanced needs of different employee groups. Employers and policy makers should adopt flexible approaches to ensure a return to workspaces that addresses employee concerns and needs.

Objective: We study employee perspectives on return to physical workspaces to ultimately inform employers’ and policy makers’ decision making around the return to work during COVID-19.Methods: We tested the three-component conceptual model using survey data collected in the United States in May 2020 from samples of energy workers (N = 333). Results: Females, non-Caucasians, and employees living in multi-generational households were less willing to return. Concerns about childcare were negatively related to willingness to return, whereas organizational strategies for mitigating COVID-19 transmission at work were positively related to willingness to return. COVID-19 infections in an employees’ network were also negatively related to employees’ willingness to return. Conclusions: Blanket policies may miss the nuanced needs of different employee groups. Employers and policy makers should adopt flexible approaches to ensure a return to workspaces that addresses employee concerns and needs.

Thermodynamic interactions in polydiene/polyolefin blends composed of 1,2-polybutadiene (1,2-PBD) and fully saturated (with deuterium) 1,2-PBD were explored with small-angle neutron scattering (SANS). Two methods were employed to extract the temperature dependence of the Flory–Huggins interaction parameter, χ, from SANS data obtained in the single-phase region. First, Zimm analysis was conducted employing data obtained at low scattering angles, providing a model-independent method of characterizing χ. Next, the random phase approximation was fit to the full angle-dependent absolute scattering intensity. The χ parameter for 1,2-PBD/saturated 1,2-PBD was found to be large in magnitude at low temperatures and exhibited a strong temperature dependence. The experimentally measured χ, at high temperatures, was in agreement with predictions of solubility parameter theory based on PVT properties of the individual components. The large and strongly temperature-dependent χ parameter of the 1,2-PBD/saturated 1,2-PBD...

We measure the dynamics of high molecular weight polystyrene grafted to silica nanoparticles dispersed in semidilute solutions of linear polymer. Structurally, the linear free chains do not penetrate the grafted corona but increase the osmotic pressure of the solution, collapsing the grafted polymer and leading to eventual aggregation of the grafted particles at high matrix concentrations. Dynamically, the relaxations of the grafted polymer are controlled by the solvent viscosity according to the Zimm model on short time scales. On longer time scales, the grafted chains are confined by neighboring grafted chains, preventing full relaxation over the experimental time scale. Adding free linear polymer to the solution does not affect the initial Zimm relaxations of the grafted polymer but does increase the confinement of the grafted chains. Our results elucidate the physics underlying the slow relaxations of grafted polymer.

Non-isothermal ultra-fast cooling crystallization tests were conducted on three blown film grade bimodal high density polyethylene (HDPE) resins using a fast differential scanning calorimeter, the Flash DSC. Non-isothermal tests were performed at cooling rates between 50 and 4000°K/s, and the data were analyzed using the modified Avrami model by Jeziorny (Polymer, 1978, 19, 1142). Non-isothermal data were used to propose a new method named crystallization–time–temperature–superposition, and the two activation energies were obtained for each of the resins. This is very useful for obtaining theoretical crystallization kinetics data at different cooling rates, allowing its use in ultra-fast cooling polymer processes such as blown film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

A facile but efficient spray-coating method was recently developed to manufacture thin, flexible, and transparent epoxy films reinforced with well-exfoliated and highly-aligned α-zirconium phosphate (ZrP) nanoplatelets in smectic liquid crystalline order. Here, we investigate the scratch resistance of ZrP/epoxy nanocomposites prepared following the same spray-coating process. Comparison was made with neat epoxy coating to determine the impact of ZrP nanofillers. Tests were conducted with accordance to ASTM D7027 /ISO 19252 scratch standard and scratch mechanisms were studied using different experimental tools. Results show that scratch resistance is considerably improved after introducing ZrP nanofillers to the epoxy coating. This was reflected by the delay in microcracking and plowing damages and the decrease of scratch coefficient of friction. This result is attributed to the significant role of exfoliated and aligned ZrP nanofillers in enhancing the mechanical properties of the epoxy matrix. The usefulness of the current study in developing new coating systems for high-performance applications is discussed.

We investigate the transport and localization of tracer probes in a glassy matrix as a function of relative size using dynamic X-ray scattering experiments and molecular dynamics simulations. The quiescent relaxations of tracer particles evolve with increasing waiting time, tw. The corresponding relaxation times increase exponentially at small tw and then transition to a power-law behavior at longer tw. As tracer size decreases, the aging behavior weakens and the particles become less localized within the matrix until they delocalize at a critical size ratio δ0 ≈ 0.38. Localization does not vary with sample age even as the relaxations slow by approximately an order of magnitude, suggesting that matrix structure controls tracer localization.

We examine the dynamics of silica particles grafted with high molecular weight polystyrene suspended in semidilute solutions of chemically similar linear polymer using X-ray photon correlation spectroscopy. The particle dynamics decouple from the bulk viscosity despite their large hydrodynamic size and instead experience an effective viscosity that depends on the molecular weight of the free polymer chains. Unlike for hard-sphere nanoparticles in semidilute polymer solutions, the diffusivities of the polymer-grafted nanoparticles do not collapse onto a master curve solely as a function of normalized length scales. Instead, the diffusivities can be collapsed across two orders of magnitude in free polymer molecular weight and concentration and one order of magnitude in grafted molecular weight by incorporating the ratio of free to grafted polymer molecular weights. These results suggest that the soft interaction potential between polymer-grafted nanoparticles and free polymer allows polymer-grafted nanoparticles to diffuse faster than predicted based on bulk rheology and modifies the coupling between grafted particle dynamics and the relaxations of the surrounding free polymer.

The mechanical properties of two chemically distinct and complementary thermoset polymers were manipulated through development of thermoset blends. The thermoset blend system was composed of an anhydride-cured diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin, contributing high tensile strength and modulus, and polydicyclopentadiene (PDCPD), which has a higher toughness and impact strength as compared to other thermoset polymers. Ultra-small-angle and small-angle X-ray scattering analysis explored the morphology of concurrently cured thermoset blends, revealing a macroscopically phase separated system with a surface fractal structure across blended systems of varying composition. The epoxy resin rich and PDCPD rich phases exhibited distinct glass transitions (Tg’s): the Tg observed at higher temperature was associated with the epoxy resin rich phase and was largely unaffected by the presence of PDCPD, whereas the PDCPD rich phase Tg systematically decreased with increasing epoxy resin content due ...

Isothermal ultra-cooling crystallization tests were conducted on three blown film grade bimodal HDPE resins using an ultrafast scanning calorimeter, the Flash DSC. Isothermal tests were performed to study the regime transition, the thermal nucleation and the spherulitical growth using the Hoffman-Lauritzen theory in a range between 90 °C and 116 °C. Temperature profile estimations using such data were in good agreement with actual blown film process data. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016.

We investigate the structure and dynamics of silica nanoparticles and polymer chains in semidilute solutions of high molecular weight polystyrene in 2-butanone to determine the effect of long-range interparticle interactions on the coupling between particle and polymer dynamics. Particles at concentrations of 1–10 wt % are well dispersed in the semidilute polymer solutions and exhibit long-range electrostatic repulsions between particles. Because the particles are comparably sized to the radius of gyration of the polymer, the particle dynamics is predicted to couple to that of the polymer. We verify that the polymer structure and dynamics are not significantly affected by the particles, indicating that the particle–polymer coupling does not change with increasing particle loading. We find that the coupling between the dynamics of comparably sized particles and polymer results in subdiffusive particle dynamics, as expected. Over the interparticle distance, however, the particle dynamics is hindered and not...

The structural transitions occurring with change in pH for aqueous mixtures of a cationic surfactant (cetyltrimethylammonium bromide, CTAB) and a hydrotrope (sodium salicylate, NaSal) were investigated at various temperatures using dynamic light scattering and small-angle neutron scattering. Direct structural studies show a transition from rigid cylindrical micelles at neutral pH to spherical micelles at ∼ pH 2 upon protonation of salicylate molecules; however, an unanticipated reversion to flexible cylindrical micelles with further decrease in pH was observed. We also observed these microstructure transitions from cylinders at high pH to spherical micelles at intermediate pH to flexible cylindrical micelles at low pH were highly sensitive to temperature. Our results suggest that, in addition to the well-described electrostatic and hydrophobic interactions in cationic surfactant-hydrotrope mixtures, the pH-induced microstructural changes are potentially governed by complementary cation-π and hydrogen bonding interactions.

The structure of aqueous dispersions of poly(oligo(ethylene oxide) monomethyl methacrylate)-grafted silica nanoparticles was characterized using contrast variation small-angle neutron scattering studies. Modeling the low hybrid concentration dispersion scattering data using a fuzzy sphere and a polydisperse core–shell model, demonstrated that the polymer chains are highly swollen in the dispersions as compared to the dimensions of the free polymer chains in dilute solution. At higher hybrid concentrations, the dispersions were well described using a Percus–Yevick approximation to describe the structure factor. These structural characterization tools are excellent starting points for effective molecular level descriptors of dewetting and macroscopic phase transitions for polymer tethered hybrid nanoparticle systems.

We determine the conformational change of polystyrene chains grafted to silica nanoparticles dispersed in deuterated cyclohexane using small-angle neutron scattering. The cyclohexane/polystyrene system exhibits an upper-critical solution temperature below which the system phase separates. By grafting the polystyrene chains to a nano-sized spherical silica particle, we observe a significant suppression in the Θ-temperature, decreasing from ≈38 °C for free polystyrene chains in d12-cyclohexane to ≈34 °C for the polystyrene-grafted nanoparticles. Above this temperature, the grafted chains are swollen and extended from the particle surface, resulting in well-dispersed grafted nanoparticles. Below this temperature, the grafted chains fully expel the solvent and collapse on the particle surface, destabilizing the nanoparticle suspension and leading to aggregation. We attribute the suppression of the Θ-temperature to a competition between entropic and enthalpic energies arising from the structure of the polymer-grafted nanoparticle in which the enthalpic terms appear to dominate.

Simulations and experiments are conducted on mixtures containing polymer grafted nanoparticles in a chemically distinct polymer matrix, where the graft and matrix polymers exhibit attractive enthalpic interactions at low temperatures that become progressively repulsive as temperature is increased. Both coarse-grained molecular dynamics simulations, and X-ray scattering and neutron scattering experiments with deuterated polystyrene (dPS) grafted silica and poly(vinyl methyl ether) PVME matrix show that the sharp phase transition from (mixed) dispersed to (demixed) aggregated morphologies due to the increasingly repulsive effective interactions between the blend components is distinct from the continuous wetting-dewetting transition. Strikingly, this is unlike the extensively studied chemically identical graft-matrix composites, where the two transitions have been considered to be synonymous, and is also unlike the free (ungrafted) blends of the same graft and matrix homopolymers, where the wetting-dewetting is a sharp transition coinciding with the macrophase separation.

The development of interpenetrating polymer networks provides a route to create tough materials that maintain high strength and stiffness, suitable for meeting the demands of an off-shore wind turbine environment. This work has focused on a system composed of diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin, contributing high tensile strength and modulus, and polydicyclopentadiene (polyDCPD), which has a higher toughness and impact strength as compared to other thermoset polymers. In situ Fourier transform infrared spectroscopy was used to explore the reaction kinetics in neat, diluted and sequentially cured mixtures of epoxy resin and polyDCPD. There were significant differences in the rate of network formation in the two neat systems, as the rate of anhydride curing of the epoxy was extremely slow at the temperatures required for reasonably measurable dicyclopentadiene (DCPD) ring-opening metathesis polymerization. The dissimilar kinetics of these two systems were leveraged in the design of a sequential curing protocol in which the DCPD was first cured in the presence of the epoxy resin components, followed by curing of the epoxy resin at an elevated temperature. The curing kinetics of the macroscopically phase separated domains of the epoxy resin components in the presence of the polyDCPD network behaved as expected for a diluted epoxy resin. These results provide the kinetic basis for future studies to prepare interpenetrating polymer networks which employ thermodynamic control of phase separation such as through the addition of compatibilizing molecules.

The interfacial behavior of water-soluble poly[oligo(ethylene oxide) monomethyl ether methacrylate], grafted from 15-nm-diameter silica nanoparticles using a living atom-transfer radical polymerization technique, was examined for hexane and water interfaces. The polymer-grafted nanoparticles reduced the hexane–water interfacial tension from ∼50 to ∼20 mN/m at concentrations of silica in the range of 1–10 ppm. The hydrodynamic size of the dispersed hybrid nanoparticle, a function of the molecular weight of the polymer and grafting density, was the dominant variable in determining the critical particle concentration and efficacy of the hybrid nanoparticles in reducing the hexane–water interfacial tension. A simple phenomenological model is used to explain the strong dependence of the critical particle concentration on the effective hydrodynamic size of the nanoparticles. Water–hexane and water–squalene emulsions formed using 1000 ppm of hybrid nanoparticles were stable for more than 60 days.

Heteroatom polymeric precursor with an aromatic substituent (polyurethane acrylate) was designed and found to generate nitrogen-doped graphene at 1000 °C. Upon thermal degradation, a nitrogenous fragment was liberated in situ. As a consequence, nitrogen-doped graphene was formed in a single step. Further, this methodology was extended for studying the effect of annealing nonheteroatom polymer with an aromatic substituent (styrene butadiene random copolymer) under similar conditions. The isolated product demonstrated undoped graphene-like structure. The mechanism of nitrogen-doped graphitization was studied by annealing different heteroatom polymer units with an aliphatic and aromatic framework in a chemical vapor deposition reactor. The effect of precursor heteroatom polymer structure and annealing temperature in the presence of copper catalyst on the efficacy of formation of nitrogen-doped graphene was examined. The nitrogen-doped graphene exhibited semiconducting behavior over semimetallic behavior of t...

We investigate the effects of geometric order and fluid rheology on the dispersion of micron-sized particles in two-dimensional microfluidic porous media. Particles suspended in a mixture of glycerol and water or in solutions of partially hydrolyzed polyacrylamide (HPAM) polymers were imaged as they flowed through arrays of microscale posts. From the trajectories of the particles, we calculated the velocity distributions and thereafter obtained the longitudinal and transverse dispersion coefficients. Particles flowed in the shear-thinning HPAM solution through periodic arrays of microposts were more likely to switch between streamlines, due to elastic instabilities. As a result, the distributions of particle velocity were broader in HPAM solutions than in glycerol-water mixtures for ordered geometries. In a disordered array of microposts, however, there was little difference between the velocity distributions obtained in glycerol-water and in HPAM solutions. Correspondingly, particles flowed through ordered post arrays in HPAM solutions exhibited enhanced transverse dispersion. This result suggests that periodic geometric order amplifies the effects of the elasticity-induced velocity fluctuations, whereas geometric disorder of barriers effectively averages out the fluctuations.

Gold nanorods grafted with short chain polymers are assembled into controlled open structures using polymer-induced depletion interactions and structurally characterized using small angle x-ray scattering. When the nanorod diameter is smaller than the radius of gyration of the depletant polymer, the depletion interaction depends solely on the correlation length of the polymer solution and not directly on the polymer molecular weight. As the polymer concentration increases, the stronger depletion interactions increasingly compress the grafted chains and push the gold nanorods closer together. By contrast, other structural characteristics such as the number of nearest neighbors and fractal dimension exhibit a non-monotonic dependence on polymer concentration. These parameters are maximal at intermediate concentrations, which are attributed to a crossover from reaction-limited to diffusion-limited aggregation. The control over structural properties of anisotropic nanoscale building blocks demonstrated here will be beneficial to designing and producing materials \emph{in situ} with specific direction-dependent nanoscale properties and provides a crucial route for advances in additive manufacturing.

A "grafting to" methodology for the attachment of a silane based polymer (SG) onto functionalized graphitic platelets is demonstrated. The siloxy end groups of the modifier were further cross-linked without addition of any external curative. These sterically stabilized nanoplatelets with a high grafting density ensured complete screening of the attractive interparticle interactions. As a result, a better dispersion of platelets was observed compared to the physically mixed platelets in the polymer matrix (SUG). The larger size of the polymer tethered graphitic particles and the greater extent of heat liberated due to grafting resulted in a higher enthalpic contribution in the case of SG compared to SUG. This makes the formation of SG thermodynamically more favorable compared to SUG. Presence of a hierarchical spatial arrangement with a good dispersion of graphitic platelets was observed within the siloxane matrix in the case of SG compared to SUG. The nanoparticle tethered composite generated exhibited an "instant" conducting adhesive behavior. The adhesive properties of the SG were found to be increased due to grafting of graphitic platelets when compared with the neat polymer. Further, SG exhibited a conductive character whereas the neat polymer and SUG demonstrated an insulating character.

We measure the mobility of nanoparticles at low concentrations in non-Newtonian semidilute aqueous solutions of high-molecular-weight polyelectrolyte polymers. Using optical microscopy and particle tracking algorithms, we image and track hydrophilic polystyrene nanoparticles of diameter 400 nm moving in aqueous solutions of partially hydrolyzed polyacrylamide of molecular weight 8 000 000 Da and concentration of 0.042—4.2 g/L. The effective diffusivity of the nanoparticles in the semidilute polymer solutions, extracted from the long-time limit of the mean-squared displacement using the Stokes–Einstein relation, is greater than that calculated from the zero-shear-rate viscosity measured using bulk rheology. For concentrations c > 0.42 g/L, the mean-square displacements (MSD) of particles measured as a function of lag time revealed that the particle dynamics are subdiffusive at short time scales and are Fickian on long time scales. The time scale for the crossover from subdiffusive to Fickian dynamics incre...

The generation of stress in expanded graphite (E-GPT) due to covalent attachment of bulky side groups connected via a hetero atom is reported. Specifically, E-GPT is modified at different levels of grafting using "click" chemistry to graft 1-ethynyl-4-fluoro benzene onto graphene sheets via a triazole ring. In the range of grafting densitites examined, Raman spectroscopy indicates that the stress generated in graphene is linearly dependent on the extent of grafting. The functionalized graphene platelets with 6% functionalization transform from semi-metal behavior of the pristine material to semi-conductor behavior and indicates the ability of functionalization to change optical and electronic properties of graphene platelets similar to the deposition of thin layers of top gate oxides onto graphene.