Download or read book Nonlinear Optical Techniques to Study Polymer Adsorption written by Ashwin B. Rao and published by . This book was released on 2006 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The adsorption of Fluorescein Isothiocyanate (FITC) labeled polystyrene at the water-toluene interface was studied by two-photon fluorescence spectroscopy. This sytem was used to develop a model to predict the concentration of polymer molecules adsorbed at the interface. For FITC labeled polystyrene of Mw: 50.5 Kg/mole, the concentration at the interface was found to be 1 mg/m2. This corresponds to an area of 82 nm2 per molecule, which indicates that the adsorbed molecules adopt a brush like conformation at the interface. The results also show the importance of accounting for fluorescence resonance energy transfer effects (FRET) in determining the concentration of the adsorbed polymers. Neglecting FRET at the interface results in an underestimation of the surface excess by a factor of 2. We have also studied the orientation of the chemical groups of poly (methyl methacrylate) (PMMA) adsorbed at the sapphire-CCI4 interface using a technique known as infrared-visible sum frequency generation spectroscopy. The ester methyl groups of PMMA are strongly oriented at the sapphire interface while the methylene and alpha methyl groups of the polymer chain appear to be disordered. The orientation of the ester methyl groups at the interface of a PMMA film and sapphire is very similar to the orientation of the ester methyl groups of an isolated PMMA chain adsorbed on sapphire. The structure of the adsorbed polymer chains is not affected by the solvent quality nor is it affected by the degree of polymerization of the chain."--Iii-iv.
Download or read book Nonlinear Optical Studies of Aqueous Interfaces Polymers and Nanowires written by Robert Michael Onorato and published by . This book was released on 2010 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the structure and composition of aqueous interfaces is one of the most important current problems in modern science. Aqueous interfaces are ubiquitous in Nature, ranging from aerosols to cellular structures. Aerosol chemistry is presently the most significant unknown factor in predicting climate change, and an understanding of the chemistry that occurs at aerosol interfaces would significantly improve climate models. Similarly, the nature of aqueous biological interfaces has a profound effect on the structure and function of proteins and other biological structures. Despite the importance of these problems, aqueous interfaces remain incompletely understood due to the challenges of experimentally probing them. Recent experimental and theoretical results have firmly established the existence of enhanced concentrations of selected ions at the air/water interface. In this dissertation, I use an interface-specific technique, UV second harmonic generation (SHG), to further investigate the adsorption of ions to the air/water interface and to extend the study of ion adsorption towards more biologically relevant systems, alcohol/water interfaces. In Chapter 2, I describe resonant UV-SHG studies of the strongly chaotropic thiocyanate ion adsorbed to the interface formed by water and a monolayer of dodecanol, wherein the Gibbs free energy of adsorption was determined to be -6.7 ± 1.1 and -6.3 ± 1.8 kJ/mol for sodium and potassium thiocyanate, respectively, coincident with the value determined for thiocyanate at the air/water interface. Interestingly, at concentrations near and above 4 M, the resonant SHG signal increases discontinuously, indicating a structural change in the interfacial region. Recent experimental and theoretical work has demonstrated that the adsorption of bromide is particularly important for chemical reactions on atmospheric aerosols, including the depletion of ozone. In Chapter 3, UV-SHG resonant with the bromide charge-transfer-to-solvent band and a Langmuir adsorption model are used to determine the affinity of bromide for both the air/water and dodecanol/water interfaces in the molar concentration regime. The Gibbs free energy of adsorption for the former is determined to be -1.4 kJ/mol with a lower 90% confidence limit of -4.1 kJ/mol. For the dodecanol/water interface the data are best fit with a Gibbs free energy of +8 kJ/mol with an estimated a lower limit of -4 kJ/mol. Adsorption of ions to the air/water interface in the millimolar regime is a particularly interesting phenomenon. In Chapter 4, the affinity of sodium chloride and sodium bromide to the air/water interface is probed by UV-SHG. Both salts exhibit a strong adsorption, with free energies greater than -20 kJ/mol. Interestingly, sodium chloride exhibits a stronger affinity for the interface than does sodium iodide, which was previously studied by Poul Peterson. This is counter to both experimental and theoretical results for higher concentrations. It has been predicted that ion adsorption is dictated by strong and opposing electrostatic and entropic forces. The change in order of ion interfacial affinity can be explained by relatively small changes in these forces at different concentrations and ionic strengths. In Chapters 5 and 6, other work using nonlinear optical techniques is described. Coherent anti-Stokes Raman scattering microscopy is a promising tool for chemically selective imaging based on molecular vibrations. While CARS is currently used as a biological imaging tool, many variations are still being developed, perhaps the most important being multiplex CARS microscopy. Multiplex CARS has the advantage of comparing images based on different molecular vibrations without changing the excitation wavelengths. In Chapter 5, I demonstrate both high spectral and spatial resolution multiplex CARS imaging of polymer films using a simple scheme for chirped CARS with a spectral bandwidth of 300 cm-1. In Chapter 6, the nonlinear optical properties of KNbO3 nanowires are studied. Using SHG and sum frequency generation, efficient nonlinear optical frequency conversion is demonstrated in single KNbO3 nanowires that act as optical waveguides, yielding a coherent tunable subwavelength light source.
Download or read book Nonlinear Optical Studies of Polymer Interfaces written by and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Froth Flotation written by Maurice C. Fuerstenau and published by SME. This book was released on 2007 with total page 910 pages. Available in PDF, EPUB and Kindle. Book excerpt: &Quot;Froth Flotation: A Century of Innovation comprehensively describes state-of-the-art research and practice in mineral froth flotation a century after its introduction. Recognized experts from around the world provide in-depth coverage on many facets of flotation, including the historical aspects; fundamentals; chemistry; flotation cells, modeling, and simulation; and flotation plant practice. This commemorative volume is an invaluable reference for industry professionals, researchers, and graduate students."--BOOK JACKET.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Relaxation Study of Poled Nonlinear Optical Polymers by Infrared Reflection Absorption Spectroscopy written by and published by . This book was released on 1993 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relaxation of poled nonlinear optical (NLO) chromophores in polymer films was characterized by infrared reflection-absorption spectroscopy. Both a guest-host system and a photocrosslinkable polymer system were investigated. Polymethylmethacrylate (PMMA) doped with either 2-methyl-4- nitroaniline (MNA) or 4(4'-nitrophenylazo) phenylamine (DO3) was studied. The photocrosslinkable polymer system, polyvinylcinnamate (PVCN) doped with 3- cinnamoyloxy-4-4-(N, N-diethylamino)-2-cinnamoyloxy phenyl azo nitrobenzene (CNNB-R) was also investigated. Doped NLO active molecules were aligned using the corona poling technique. Infrared spectra as a function of time were used to monitor the relaxation behavior of the oriented dyes after poling. Relaxation of NLO molecules was followed at various characteristic vibrational frequencies. The relaxation of MNA was found to be faster than that of DO3. The NLO dye molecule, CNNB-R was covalently bonded to the host polymer and formed a three dimensional crosslinked network after ultraviolet (UV) irradiation. Relaxation of NLO molecules in pristine and UV treated samples were compared. UV light induced crosslinking provided better temporal stability of molecular alignment in this system ... Nonlinear optical polymer, Photocrosslinkable polymer, Guest- host system.
Download or read book Comparative Assessment of Different Poling Techniques of Nonlinear Optical Polymers by Optical Second Harmonic Generation written by Siu Wai Chan and published by . This book was released on 2003 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nonlinear Optical Studies of Molecular Adsorption and Solvation at Solid liquid and Liquid liquid Interfaces written by Antonie Renee Siler and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Novel Methods of Approach to the Design and Synthesis of Nonlinear Optical Polymers for Optoactive Applications written by Sanjoy Mullick and published by . This book was released on 1996 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Second order Nonlinear Optical Characterization Techniques written by Thierry Verbiest and published by CRC Press. This book was released on 2009-02-19 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although chemists, biochemists, biologists, and material scientists are often interested in using nonlinear optical techniques for characterizing their samples, they seldom have the necessary background to exploit these methods. Designed for nonspecialists, Second-Order Nonlinear Optical Characterization Techniques: An Introduction focuses on the p
Download or read book Methods for Determining Polymer Adsorption on Clays written by Melanie Marie Miller and published by . This book was released on 1985 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fundamentals of Sum Frequency Spectroscopy written by Y. R. Shen and published by Cambridge University Press. This book was released on 2016-02-18 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first book on the topic, and written by the founder of the technique, this comprehensive resource provides a detailed overview of sum-frequency spectroscopy, its fundamental principles, and the wide range of applications for surfaces, interfaces, and bulk. Beginning with an overview of the historical context, and introductions to the basic theory of nonlinear optics and surface sum-frequency generation, topics covered include discussion of different experimental arrangements adopted by researchers, notes on proper data analysis, an up-to-date survey commenting on the wide range of successful applications of the tool, and a valuable insight into current unsolved problems and potential areas to be explored in the future. With the addition of chapter appendices that offer the opportunity for more in-depth theoretical discussion, this is an essential resource that integrates all aspects of the subject and is ideal for anyone using, or interested in using, sum-frequency spectroscopy.
Download or read book Linear and Nonlinear Optical Studies of Molecular Adsorption to Silica liquid Interfaces written by Brittany Lauren Gray Woods and published by . This book was released on 2015 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adsorption mechanisms at buried interfaces are difficult to predict a priori, with many interactions to consider including those between the substrate and solvent, the substrate and adsorbate, and the solvent and adsorbate. Studies described in this thesis examine the roles these variables have on controlling interfacial behavior, including molecular adsorption and aggregation at solid/liquid interfaces. Specifically, second harmonic generation (SHG) was employed to characterize adsorption environments and adsorption energies at different silica/liquid interfaces, due to the technique's surface specificity. Additionally, time resolved fluorescence was used to quantify emission lifetimes within these same interfacial regions. By systematically changing the substrate, solvent identity, and adsorbate functionality, the impact of each contribution was identified and quantified. Initial studies examined the role played by interfacial pH in controlling adsorption. Above pH 5, silica surfaces become negatively charged and promote two distinct adsorption mechanisms. Adsorption due to these mechanisms requires very long equilibration times (>3hrs). Subsequent experiments studied the role played by solvent identity on interfacial solvation. At a methanol/silica interface a non-polar interfacial environment was produced, independent of solute choice. Non-polar solvents conversely create polar interfacial solvation environments. At these different solid/liquid interfaces, similarly structured coumarin dyes, C151 and C152, were examined. Slight changes in structure lead to differing behaviors at the surface, C151 terminates at monolayer coverage while C152 shows clear signs of multilayer formation. This observation is explained by the difference in hydrogen bonding opportunities for each adsorbate: C151 can accept and donate H-bonds while C152 can only accept H-bonds, resulting in more degrees of freedom for C152 at an interface and thus the possibility of aggregation.
Download or read book Design Synthesis and Characterization of Novel Nonlinear Optical Polymers written by and published by . This book was released on 1996 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal focus of the project is to research and develop new polymeric materials based on molecular level design and solid state chemistry. The goals have been to develop electroactive polymers with novel electronic, optical and nonlinear optical properties.
Download or read book Advanced Electromagnetic Waves written by Saad Bashir and published by BoD – Books on Demand. This book was released on 2015-11-18 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book endeavors to give the reader a strong base in the advanced theory of electromagnetic waves and its applications, while keeping pace with research in various other disciplines that apply electrostatics/electrodynamics theory. The treatment is highly mathematical, which tends to obscure the principles involved.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1988 with total page 1132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Theoretical Studies of Second order Nonlinear Optical Properties of a Chromophore functionalized Polymer written by Millicent Anne Firestone and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
