Current Perspective on the Study of Liquid-Fluid Interfaces: From Fundamentals to Innovative Applications

Fluid interfaces are promising candidates for confining different types of materials - e.g., polymers, surfactants, colloids, and even small molecules - and for designing new functional materials with reduced dimensionality. The development of such materials requires a deepening of the Physico-chemical bases underlying the formation of layers at fluid interfaces, as well as on the characterization of their structures and properties. This is of particular importance because the constraints associated with the assembly of materials at the interface lead to the emergence of equilibrium and dynamics features in the interfacial systems, which are far from those conventionally found in the traditional materials. This Special Issue is devoted to studies on fundamental and applied aspects of fluid interfaces, trying to provide a comprehensive perspective on the current status of the research field

New Methods To Assess Protein Folding And Conformational Dynamics

A protein’s folding and conformational energy landscape depends on a large number of molecular degrees of freedom and interactions. As a result, different proteins can follow different sequences of events moving toward the native state along the course of folding. For example, the underlying structural organization and ordering can occur locally first and then globally, or vice versa. In addition, the associated conformational transitions can take place over a wide range of timescales. Because of these complexities, arriving at a detailed assessment and understanding of the folding dynamics and mechanism of any protein via a single type of experiment is challenging, and sometimes impossible. As such, over the past two decades, many different experimental methods have been employed to study how proteins fold among which, the laser-induced temperature-jump (T-jump) technique has emerged as a powerful tool to measure protein folding kinetics occurring on the nanosecond and microsecond timescales. Herein, we further expand the utility of the T-jump technique. First, we introduce a new form of the T-jump technique (referred to as VIPT-jump) that can be used to distinguish between different folding mechanisms. Second, we apply the VIPT-jump concept to better understand the folding dynamics of an alanine-based -helix, and, in conjunction with theoretical modeling, we are able to determine the long-sought microscopic rate constants of the helical nucleation and propagation processes. Third, we develop a new method to extend the time window of observation in a T-jump experiment to the millisecond timescale. In a parallel effort, we demonstrate that quenching the fluorescence of a dye molecule by a tryptophan residue via photoinduced electron transfer mechanism can be used to interrogate the conformational dynamics of proteins that are crucial for function. Applying this method to the M2 proton channel of the Influenza A virus allow us to determine, for the first time, the gating dynamics of the tryptophan tetrad in this membrane protein

Multi-scale Computational Studies of Waterborne Coatings.

In this thesis, we apply multi-scale molecular dynamics (MD) simulations to enhance understanding of the molecular-level structure and interactions in waterborne coatings that is needed to go beyond the current trial-and-error methods of formulating them. We use atomistic simulations reveal the properties of the latex binder/water interface including the persistence of hydrogen bonds formation and interfacial water dynamics. We also develop a new method using a weighted histogram analysis method (WHAM) to calculate the free energy differences between of micelles of various sizes, and use this to determine the size distribution of the flower-like micelles formed by model hydrophobically modified ethoxylated urethane (HEUR) polymer rheology modifiers, containing an alkane hydrophobe at each end of the chain. We also use WHAM and first passage time analysis to determine the times required for hydrophobes to escape from micelles and from the latex surfaces. We find, for example, that these escape times from a latex surface are more than an order of magntidue larger than for the same hydrophobe from a micelle. This implies that a direct bridge of a latex particle to another latex particle via a HEUR molecule will persist longer than a bridge of a particle to a HEUR micelle, and that these direct particle-to-particle bridges likely dominate the important rheological time sclaes of the latex suspension. These results help reveal the molecular structures of waterborne coatings that are responsible for the rheological properties of the coatings, such as their modulus, relaxation times, and shear thinning.PHDChemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113399/1/fangyuan_1.pd

Doctor of Philosophy

dissertationThe air pollution inversions in the mountain west are a societal problem that require a large-scale solution. With the more stringent Environmental Protection Agency (EPA) regulations established in 2010, and the recent discovery of the photocatalytic pollution reduction capabilities of titanium dioxide (TiO2), interest has developed to create pollution-reducing construction materials. Over the last decade, a number of laboratory studies have been performed and a few field studies have occurred around the world. There are commercially available photocatalytic materials that can be used in concrete construction; however, the materials are often cost prohibitive. This study investigated both practical application techniques and the effects of the climatic environment around the specimens. When concrete specimens were exposed to the weather for 120-days, the specimen's photocatalytic efficiency decreased significantly. Rejuvenation methods were investigated; however, no methods tested were able to increase the photocatalytic efficiency of the specimens to preweathered condition. The final element of this study focused on identifying practical and cost-effective methods of adding TiO2 to current production methods by working with a local precast manufacturer. This research is a stepping stone to develop methodologies to minimize the decline of photocatalytic efficiency due to the exposure to the environment. This element is critical in understanding this complex technology and identifying problems that need to be addressed before products are ready for widespread use

Some aspects of transport properties at high pressures (Modern aspects of physical chemistry at high pressure : the 50th commemorative volume)

We present a review of transport properties i.e., self-diffusion, viscosity and thermal coductivity coefficients at high pressure. The pressure range of experimental results covered by this analysis will depend on the property or the effect which is studied. As the density is the relevant parameter, the density range includes moderately dense gases, dense gases, liquids, and solids. Particular attention is given to some regions of the phase diagram, as the liquid-solid transition or the critical region, where large variations of some of the transport properties are observed. Finally experimental data are compared with theoretical predictions based on Enskog's theory, modified Enskog's theory and computer simulations

Development of sensors and non-destructive techniques to determine the performance of coatings in construction

The primary objective of this work was to examine and develop techniques for monitoring the degradation of Organically Coated Steel (OCS) in-situ. This included the detection of changes associated with the weathering to both the organic coating and metallic substrate. Initially, a review of current promising techniques was carried out however many were found to be unsuitable for this application and the adaptation of current techniques and the development of new techniques was considered. A brief concept investigation, based on initial testing and considerations, was used to determine a number of sensing techniques to examine. These included embedded, Resonant Frequency Identification (RFID), Magnetic Flux Leakage (MFL) and dielectric sensing. Each of these techniques were assessed for the application, prototyped, and tested against a range of samples to determine the accuracy and sensitivity of degradation detection provided. A range of poorly and highly durable coated samples were used in conjunction with accelerated weathering testing for this aim. Track based electronic printed sensors were presented as both a cut edge corrosion tracking and coating capacitance measurement method. While suffering somewhat from electrical paint compatibility issues both concepts showed merit in initial trials however the capacitive sensor ultimately proved insufficiently responsive to coating changes. The embedded, progressive failure-based, cut edge corrosion sensor was produced and tested in modern coating systems with moderate success. Novel applications of RFID and MLF techniques were considered and proved capable of detecting large changes in substrate condition due to significant corrosion. However, there was a lack of sufficient sensitivity when considering early-stage corrosion of durable modern OCS products. Finally, it was shown that a chipless antenna could be designed and optimised for novelly monitoring the changes to the dielectric properties of a paint layer due to degradation. However, ultimately this test, due to equipment requirements, lent itself more to lab testing than in-situ. Due to some of these limitations a different approach was considered in which the environmental factors influencing degradation were examined with the aim of relating these to performance across a building. It was observed that a combination of high humidity and the build-up of aggressive natural deposits contributed to high degradation rates in sheltered regions, such as building eaves, where microclimates were created. The build-up of deposits and their effect was presented as a key degradation accelerant during in-use service. A unique numerical simulation approach was developed to predict the natural washing, via rain impact and characteristics of the building analysed. This approach showed promise for determining areas unlikely to be naturally washed, and therefore subjected to a degradation accelerating, build-up of deposits. Given these understandings coated wetness sensors were considered as a realistic live-monitoring device capable of determining deposit build up and ultimately OCS lifetime

Solid state NMR of acid anhydride/hydroxyl crosslinking systems

This thesis is concerned with the study by solid-state NMR of the polymers formed by acid anhydride/hydroxyl cross-linking systems. The polymers studied in this thesis are based on a copolymer containing either itaconic or maleic anhydride which cross-Jinks with a polyester tipped with triethanolamine. The mobility of the polyester chains in the cross-linked films is probed by solid-state NMR, and the kinetics of the cure between acid anhydride/hydroxyi systems is discussed. The degradation of the cross-Jinked films is studied by (^13)C solid-state NMR. The films are shown to undergo hydrolysis when subjected to their exposure environment. The theory behind transient nuclear Overhauser effects in the solid state is discussed, and comparisons are made between the theoretical simulations and the experimented data for the cross—linked films. Lastly, a solid-state heteronuclear NOESY experiment is presented for a (^13)C(_2)-enriched acid anhydride/hydroxyl cross-linked film

Aspects on Fundaments and Applications of Conducting Polymers

Since the establishment of the conductive properties of intrinsic conductive polymers, a huge variety of basic and applied research has been carried out, involving different polymers, copolymers, blends, mixtures and composites. Thus, fundamental understanding of physical and chemical properties of these materials has been sought, while the applied aspects have advanced very rapidly, crossing the boundaries between disciplines. Today, the applications of conducting polymers in various fields such as neuroscience, nanotechnology and green chemistry, are easily found. This development is dynamic and it needs to be updated and hence the motivation for the set of results presented in this book; which provides information about the development of fundamentals, and about some applications of conductive polymers