Download or read book Sum Frequency Generation SFG Surface Vibrational Spectroscopy and Atomi Force Microscopy AFM Studies of the Composition Structure and Mechanical Behavior of Polymers at Interfaces written by Aric Martin Opdahl and published by . This book was released on 2003 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of the Molecular Structure and Mechanical Properties Polymer Surfaces and Protein polymer Interfaces by Sum Frequency Generation Vibrational Spectroscopy and Atomic Force Microscopy written by Telly Stelianos Koffas and published by . This book was released on 2004 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gels Genes Grafts and Giants written by Stuart Cooper and published by CRC Press. This book was released on 2005-04-15 with total page 931 pages. Available in PDF, EPUB and Kindle. Book excerpt: In celebration of Allan Hoffman’s 70th birthday, a symposium entitled Gels, Genes, Grafts and Giants was held in Maui in December 2002. This symposium, organized by The University of Washington Engineered Biomaterials (UWEB) NSF Engineering Research Center, was a great success, with many excellent papers presented by scientists from all over the world. All those who made oral or poster presentations at the symposium, but also those who worked with Allan Hoffman in the past or worked in similar research areas were invited to submit articles for special issues of the Journal of Biomaterials Science, Polymer Edition. The papers from these special issues of the journal have now been published in one hardcover book.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of the Molecular Structure and Mechanical Properties of Polymer Surfaces and Protein written by and published by . This book was released on 2004 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and other complementary surface-sensitive techniques have been used to study the surface molecular structure and surface mechanical behavior of biologically-relevant polymer systems. SFG and AFM have emerged as powerful analytical tools to deduce structure/property relationships, in situ, for polymers at air, liquid and solid interfaces. The experiments described in this dissertation have been performed to understand how polymer surface properties are linked to polymer bulk composition, substrate hydrophobicity, changes in the ambient environment (e.g., humidity and temperature), or the adsorption of macromolecules. The correlation of spectroscopic and mechanical data by SFG and AFM can become a powerful methodology to study and engineer materials with tailored surface properties. The overarching theme of this research is the interrogation of systems of increasing structural complexity, which allows us to extend conclusions made on simpler model systems. We begin by systematically describing the surface molecular composition and mechanical properties of polymers, copolymers, and blends having simple linear architectures. Subsequent chapters focus on networked hydrogel materials used as soft contact lenses and the adsorption of protein and surfactant at the polymer/liquid interface. The power of SFG is immediately demonstrated in experiments which identify the chemical parameters that influence the molecular composition and ordering of a polymer chain's side groups at the polymer/air and polymer/liquid interfaces. In general, side groups with increasingly greater hydrophobic character will be more surface active in air. Larger side groups impose steric restrictions, thus they will tend to be more randomly ordered than smaller hydrophobic groups. If exposed to a hydrophilic environment, such as water, the polymer chain will attempt to orient more of its hydrophilic groups to the surface in order to minimize the total surface energy. With an understanding of the structural and environmental parameters which govern polymer surface structure, SFG is then used to explore the effects of surface hydrophobicity and solvent polarity on the orientation and ordering of amphiphilic neutral polymers adsorbed at the solid/liquid interface. SFG spectra show that poly(propylene glycol) (PPG) and poly(ethylene glycol) (PEG) adsorb with their hydrophobic moieties preferentially oriented toward hydrophobic polystyrene surfaces. These same moieties, however, disorder when adsorbed onto a hydrophilic silica/water interface. Water is identified as a critical factor for mediating the orientation and ordering of hydrophobic moieties in polymers adsorbed at hydrophobic interfaces. The role of bulk water content and water vapor, as they influence hydrogel surface structure and mechanics, continues to be explored in the next series of experiments. A method was developed to probe the surface viscoelastic properties of hydroxylethyl methacrylate (HEMA) based contact lens materials by analyzing AFM force-distance curves. AFM analysis indicates that the interfacial region is dehydrated, relative to the bulk. Experiments performed on poly(HEMA+MA) (MA = methacrylic acid), a more hydrophilic copolymer with greater bulk water content, show even greater water depletion at the surface. SFG spectra, as well as surface energy arguments, suggest that the more hydrophilic polymer component (such as MA) is not favored at the air interface; this may explain anomalies in water retention at the hydrogel surface. Adsorption of lysozyme onto poly(HEMA+MA) was found to further reduce near-surface viscous behavior, suggesting lower surface water content. Lastly, protein adsorption is studied using a model polymer system of polystyrene covalently bound with a monolayer of bovine serum albumin. SFG results indicate that some amino acid residues in proteins adopt preferred orientations. SFG spectra also show that the phenyl rings of the bare polystyrene substrate in contact with air or liquid are ordered, with a dipole component directed along the surface normal, but slightly disorder after protein adsorption. Differences in AFM friction values suggest that protein interacts more strongly with the polystyrene substrate at the air/solid interface. The molecular orientation and ordering of surface phenyl groups are also shown to affect substrate hydrophobicity.
Download or read book Low Energy Electron Diffraction LEED and Sum Frequency Generation SFG Vibrational Spectroscopy Studies of Solid vacuum Solid air and Solid liquid Interfaces written by Saskia Hoffer and published by . This book was released on 2002 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Directory of Graduate Research written by American Chemical Society. Committee on Professional Training and published by . This book was released on 2005 with total page 1932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
Download or read book Mechanical Properties of Polymers Measured through AFM Force Distance Curves written by Brunero Cappella and published by Springer. This book was released on 2016-07-14 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Springer Laboratory volume is a practical guide for scientists and students dealing with the measurement of mechanical properties of polymers at the nanoscale through AFM force-distance curves. In the first part of the book the reader will find a theoretical introduction about atomic force microscopy, focused on force-distance curves, and mechanical properties of polymers. The discussion of several practical issues concerning the acquisition and the interpretation of force-distance curves will help scientists starting to employ this technique. The second part of the book deals with the practical measurement of mechanical properties of polymers by means of AFM force-distance curves. Several "hands-on" examples are illustrated in a very detailed manner, with particular attention to the sample preparation, data analysis, and typical artefacts. This section gives a complete overview about the qualitative characterization and quantitative determination of the mechanical properties of homogeneous polymer samples, polymer brushes, polymer thin films, confined polymer samples, model blends and microstructured polymer blends through AFM force-distance curves. The book also introduces to new approaches and measurement techniques, like creep compliance and force modulation measurements, pointing out approximations, limitations and issues requiring further confirmation.
Download or read book Molecular level Structures of Polymer Surfaces and Interfaces Studied by Sum Frequency Generation Vibrational Spectroscopy written by Chunyan Chen and published by . This book was released on 2005 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sum frequency Spectroscopic Studies written by and published by . This book was released on 2000 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface vibrational spectroscopy via infrared-visible sum-frequency generation (SFG) has been established as a useful tool to study the structures of different kinds of surfaces and interfaces. This technique was used to study the (0001) face of hexagonal ice (Ih). SFG spectra in the O-H stretch frequency range were obtained at various sample temperatures. For the vapor(air)/ice interface, the degree of orientational order of the dangling OH bonds at the surface was measured as a function of temperature. Disordering sets in around 200 K and increases dramatically with temperature, which is strong evidence of surface melting of ice. For the other ice interfaces (silica/OTS/ice and silica/ice), a similar temperature dependence of the hydrogen bonded OH stretch peak was observed; the free OH stretch mode, however, appears to be different from that of the vapor (air)/ice interface due to interactions at the interfaces. The technique was also used to measure the orientational distributions of the polymer chains on a rubbed polyvinyl alcohol surface. Results show that the polymer chains at the surface appear to be well aligned by rubbing, and the adsorbed liquid crystal molecules are aligned, in turn, by the surface polymer chains. A strong correlation exists between the orientational distributions of the polymer chains and the liquid crystal molecules, indicating that the surface-induced bulk alignment of a liquid crystal film by rubbed polymer surfaces is via an orientational epitaxy-like mechanism. This thesis also contains studies on some related issues that are crucial to the above applications. An experiment was designed to measure SFG spectra in both reflection and transmission. The result confirms that SFG in reflection is generally dominated by the surface contribution. Another issue is the motional effect due to fast orientational motion of molecules at a surface or interface. Calculations show that the effect is significant if the molecular orientation varies over a broad range within the vibrational relaxation time. The stretch vibration of the free OH bonds at the vapor/water interface is used to illustrate the importance of the effect.
Download or read book Probing the Structure and Nano scale Mechanical Properties of Polymer Surfaces with Scanning Force Microscopy and Sum Frequency Vibrational Spectroscopy written by David Hugo Gracias and published by . This book was released on 1999 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applications of Scanned Probe Microscopy to Polymers written by James Daryl Batteas and published by . This book was released on 2005 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Applications of Scanned Probe Microscopy to Polymers stresses the analysis of polymer and biopolymer surfaces using the ever-expanding methodologies of scanned probe microscopies. This book includes studies of optical properties by near-field methodologies, local mechanical properties of polymer films by AFM, the dynamics and mechanics of single molecules probed by AFM, and methodologies for enhanced imaging modes. A primary focus of this book is the quantitative measurement of surface properties by scanned probe techniques, which illustrates how the field has evolved and what new challenges lie ahead. Applications of Scanned Probe Microscopy to Polymers will be valuable to students and professionals looking for studies that illustrate what types of polymer material properties may be probed by scanned probe microscopies.
Download or read book Improvements on the Analysis and Instrumentation for Sum Frequency Generation Spectroscopy and Microscopy written by Joon Hee Jang and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sum frequency generation (SFG) vibrational spectroscopy has been established as one of the most essential tools to investigate chemistry of the surfaces and interfaces for several decades. Orientation, structure, and chemical reaction of molecules at the interfaces have been examined by using temporally and spatially resolved SFG. As a unique method to observe the chemistry at the interfaces, SFG has a great potential for further developments. In this dissertation, the possibility of extending the SFG field is gauged, including the introduction of detailed theory and formulation of SFG. Firstly, the principle of sum frequency vibrational depletion spectroscopy (SVDS) technique is presented. Newly developed SVDS has been established for observing vibrational behaviors of molecules on the surface with high spatial resolution below the diffraction limit. This technique is accomplished by depletion of the ground state molecules around the center of probing focal spot on the surface. High energy density IR generated is employed to deplete the ground state molecules to its first vibrational excited state. Then, SFG technique has been conducted to measure the vibrational dipoles of the surface molecules from the confined probing area. The instrumentation, theoretical simulation, depletion efficiency and the preliminary experimental results of this technique is reported. In the following chapter, SFG from acetonitrile on rutile TiO2 (110) surface has been measured using distinct polarization combinations and compared to the spectra obtained by polarization mapping and null angle methods. By varying the polarization combinations of SFG, the magnitude and shape of the spectra undergo substantial change, originating from the interference between the non-resonant signal inherent from the rutile substrate and the resonant signal from the adsorbed molecules. Theory, simulation, and analytical methods for obtaining quantitative orientation information in the presence of non-resonant signal of the adsorbed molecules on a semiconductor are presented. In the last chapter, a refined analytical procedure for SFG imaging microscope (SFGIM) is discussed. In order to determine the surface properties, the images need to be fitted using an SFG model equation which contains the physical properties relevant to interpret the surface. Experimental results obtained from SFGIM analysis of binary system of self-assembled monolayers on gold surface have been reported.
Download or read book Vibrational Spectroscopy at Electrified Interfaces written by Andrzej Wieckowski and published by John Wiley & Sons. This book was released on 2013-07-15 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews the latest theory, techniques, and applications Surface vibrational spectroscopy techniques probe the structure and composition of interfaces at the molecular level. Their versatility, coupled with their non-destructive nature, enables in-situ measurements of operating devices and the monitoring of interface-controlled processes under reactive conditions. Vibrational Spectroscopy at Electrified Interfaces explores new and emerging applications of Raman, infrared, and non-linear optical spectroscopy for the study of charged interfaces. The book draws from hundreds of findings reported in the literature over the past decade. It features an internationally respected team of authors and editors, all experts in the field of vibrational spectroscopy at surfaces and interfaces. Content is divided into three parts: Part One, Nonlinear Vibrational Spectroscopy, explores properties of interfacial water, ions, and biomolecules at charged dielectric, metal oxide, and electronically conductive metal catalyst surfaces. In addition to offering plenty of practical examples, the chapters present the latest measurement and instrumental techniques. Part Two, Raman Spectroscopy, sets forth highly sensitive approaches for the detection of biomolecules at solid-liquid interfaces as well as the use of photon depolarization strategies to elucidate molecular orientation at surfaces. Part Three, IRRAS Spectroscopy (including PM-IRRAS), reports on wide-ranging systems from small fuel molecules at well-defined surfaces to macromolecular complexes that serve as the building blocks for functional interfaces in devices designed for chemical sensing and electric power generation. The Wiley Series on Electrocatalysis and Electrochemistry is dedicated to reviewing important advances in the field, exploring how these advances affect industry. The series defines what we currently know and can do with our knowledge of electrocatalysis and electrochemistry as well as forecasts where we can expect the field to be in the future.
Download or read book Vibrational Sum Frequency Generation Studies of Aqueous and Biological Relevant Interfaces written by Ping Yuan Hsu and published by . This book was released on 2011 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: The molecular structures of soft or fluid-like surfaces during contact in aqueous media play an important role in understanding adhesion and wetting between colloidal and biological interfaces. For example, it has been suggested that the presence of bound water (hydration layer) is crucial in controlling the fusion of lipid bilayers and the adsorption of proteins to bio-materials. Interfacial force measurements have revealed the importance of interfacial molecular structures on the viscosity, lubricity and adhesion acting between two surfaces. However, force measurements cannot provide direct information of the molecular structure after contact. Due to the limitations of experimental techniques, the understanding about the molecular structures of soft contact interfaces is limited. In this dissertation, we have developed an experimental approach to study the contact interface between a liquid and a solid substrate in an environment where they are surrounded by water. The surface sensitive infrared-visible sum frequency generation spectroscopy (SFG) provides information on the chemical groups, concentration and orientation of the molecules at the interface. We have studied the interface between hexadecane and sapphire surface using this technique. The adhesion between hexadecane droplets and the sapphire surface are determined by pH and the isoelectric point of sapphire substrate. Also, the SFG results suggest that the oil does not come in direct contact with the sapphire surface but is separated by a thin layer of water, even though the oil droplet sticks to the sapphire surface. The presence of the surfactant generates heterogeneous patchy contact between the oil and the sapphire, where the methyl groups of hexadecane are in direct contact with the surface hydroxyl groups of the sapphire surface. We have also used this design to study the contact interface between surfactant (stearyl trimethyl ammonium bromide, STAB) monolayers to mimic lipid bilayer contact. We have taken advantage of the adsorption of STAB on polystyrene and on hexadecane to create a contact interface with surfactant molecules on both sides. At conditions when both the surfaces were saturated with the surfactant molecules, it was impossible to drain the water away and the spectral signature of water did not change. This indicated that the double layer forces were strong enough to prevent any drainage of water at the fluid-like interface. In addition, the structure of water remained the same which is consistent with the expectations from force measurements that water structure is only affected under confinement and between two rigid and flat substrates. We also studied soft contact interface between elastomeric poly-dimethyl siloxane lenses and sapphire in water by using SFG. The confined spectra showed peaks related to PDMS as well as water, suggesting formation of water puddles in the contact area. The presence of the peak at 3690 cm-1 suggests the contact of surface hydroxyl groups with PDMS, supporting our hypothesis that the contact is heterogeneous. This heterogenous picture provides insight into the higher friction for a rubber sliding on sapphire surface in the presence of water. By using the established experimental protocols of SFG and the matrix free nanoassisted laser desorption-ionization (NALDI) mass spectroscopy, the actual adhesive contact interface between the soft gecko toe pad and the sapphire substrate was determined. A gecko's stickiness derives from van der Waals interactions between proteinaceous hairs called setae and the substrate. However, the molecular structure of the immediate contact at the adhesive interface is unknown. The SFG experiments demonstrate that there is a high representation of C-H bonds at the interface during gecko/sapphire contact, but the signatures of O-H bonding (e.g. water) and aromatic groups (e.g. amino acids/proteins) are entirely absent. Our discovery and analysis of gecko footprints have led to a surprising finding that geckos left behind a distinct trace of phospholipid molecules, a material that has never been considered in papers that deal with gecko adhesion. Particularly interesting ramifications include the previously unexplained sensitivity of gecko shear adhesion to variation in humidity, and the observation that setae show little if any wear. In the former case we find that an increase in the surface exposure of methylene groups is correlated with exposure of setae to water. In the latter case, it may be that sacrificial lipid-like molecules prevent damage to the rigid setae made of [Beta]-keratin. Our analysis of gecko footprints and the toe pad/substrate interface has significant consequences for models of gecko adhesion and by extension, the design of synthetic mimics.
Download or read book Probing the Structure and Nano scale Mechanical Properties of Polymer Surfaces with Scanning Force Microscopy and Sum Frequency Vibrational Spectroscopy written by and published by . This book was released on 1999 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Vibrational Spectroscopy of Polymers written by D. I. Bower and published by Cambridge University Press. This book was released on 1992-07-16 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes the theory and practice of infrared and Raman spectroscopy as applied to the study of the physical and chemical characteristics of polymers. Its purpose is to give the beginning researcher in the field a firm foundation and a starting point for the study of more advanced literature. To this end the book concentrates on the fundamentals of the theory and nomenclature, and on the discussion of well-documented illustrations of these fundamental principles, including many now-classic studies in the subject. No previous knowledge of either polymers or vibrational spectroscopy is assumed.
