Interim Proposal for Molecular Beam Studies of Surfactants in Sulfuric Acid Aerosols: Comparisons Between Hydrocarbon and Fluorocarbon Alcohols PDF Download
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Languages : en
Pages : 6
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Heterogeneous reactions of gas phase molecules with aqueous sulfuric acid aerosols play a significant role in the destruction of ozone in the stratosphere. These processes include the acid-catalyzed reactions of HCI and HBr with CIONO2 (BrONO2) and HOCI (HOBr) to generate photoactive halogen molecules, particularly in colder regions of the stratosphere where they are more soluble in the water-rich aerosols. Our objective is to determine the mechanisms and rate-limiting steps of reactions of these atmospheric gases with these supercooled sulfuric acid droplets. By employing molecular beam scattering techniques, we probe the nature of the initial gas-sulfuric acid collision and the immediate fate of HCI and HBr molecules trapped at the acid's surface as they either desorb into the gas phase or react in the interfacial or bulk regions of the aerosol. In this interim grant period, we have explored the ability of organic molecules dissolved in sulfuric acid to form surface films that impede gas uptake and thereby reduce the rates of heterogeneous reactions in the acid. These surface-active organic molecules are found naturally in the upper troposphere and tropopause and may be produced in the exhaust of jet aircraft. We have so far investigate the entry of trifluoroethanol and HCI gas molecules into bare sulfuric acid and acid coated with butanol, dodecanol, and hexadecanol. These hydrocarbon surfactants have kept us busy, and we have not yet compared them with fluorocarbon ones.
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Publisher:
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Category :
Languages : en
Pages : 6
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Book Description
Heterogeneous reactions of gas phase molecules with aqueous sulfuric acid aerosols play a significant role in the destruction of ozone in the stratosphere. These processes include the acid-catalyzed reactions of HCI and HBr with CIONO2 (BrONO2) and HOCI (HOBr) to generate photoactive halogen molecules, particularly in colder regions of the stratosphere where they are more soluble in the water-rich aerosols. Our objective is to determine the mechanisms and rate-limiting steps of reactions of these atmospheric gases with these supercooled sulfuric acid droplets. By employing molecular beam scattering techniques, we probe the nature of the initial gas-sulfuric acid collision and the immediate fate of HCI and HBr molecules trapped at the acid's surface as they either desorb into the gas phase or react in the interfacial or bulk regions of the aerosol. In this interim grant period, we have explored the ability of organic molecules dissolved in sulfuric acid to form surface films that impede gas uptake and thereby reduce the rates of heterogeneous reactions in the acid. These surface-active organic molecules are found naturally in the upper troposphere and tropopause and may be produced in the exhaust of jet aircraft. We have so far investigate the entry of trifluoroethanol and HCI gas molecules into bare sulfuric acid and acid coated with butanol, dodecanol, and hexadecanol. These hydrocarbon surfactants have kept us busy, and we have not yet compared them with fluorocarbon ones.
Author: Ke Wang
Publisher: Uppsala Universitet
ISBN: 9789155445645
Category : Science
Languages : en
Pages : 49
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Author: Jaisree Kannan Iyer
Publisher:
ISBN:
Category :
Languages : en
Pages : 281
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Fluorinated surfactants are an important class of surfactants because they possess properties that are far superior than those of their hydrocarbon analogs. As a result, they are used in a wide variety of applications including in paints, polishes, fire-fighting foams, and emulsion polymerization processes. However, concerns regarding the non-biodegradability and toxicity of fluorinated surfactants have prompted the search for new, benign alternative surfactant formulations that possess micellization properties comparable to those of traditional fluorinated surfactants. With this need in mind, this thesis focuses on gaining a molecular-level understanding of the micellization behavior of traditional fluorinated surfactants, and then using the acquired knowledge to design novel surfactant formulations that can reduce the use of fluorinated surfactants. Molecular-thermodynamic (MT) models were developed to calculate the various contributions to the free energy of micellization for discoidal and biaxial ellipsoidal micelles; two important micelle shapes in the context of fluorocarbon-based surfactants. These models explicitly incorporate the effect of the position-dependent curvature associated with discs and biaxial ellipsoids. Comparison between the models developed here with those that do not explicitly account for the varying curvature shows that accounting for the position-dependent curvature is extremely important in modeling these two micelle shapes. The new MT model for the free energy of micellization is also used to demonstrate the feasibility of realizing biaxial ellipsoidal micelles, a result refuted in the past in many theoretical studies on the basis of average geometrical properties of the micelle. A new computer-simulation-molecular-thermodynamic (CSMT) framework was developed to predict the micellization behavior of mixtures of fluorocarbon-based surfactants. To facilitate the practical implementation of the mixture CSMT framework, which involves the computationally intensive task of simulating several mixed micelles, an approximation to the mixture CSMT model was developed. In this approximation, relevant properties for a mixed micelle are estimated using a micelle-composition based weighted average of the analogous properties obtained from simulations of the single-component surfactant micelles for each of the surfactants comprising the mixture. Therefore, in this approximation, the need for simulating mixed micelles is eliminated. The approximation was found to compare well with the mixture CSMT model for various binary surfactant mixtures considered, except for those containing alkyl ethoxylate surfactants. A rationalization of this finding is presented. CMC predictions made using the mixture CSMT model were found to compare very well with the experimental CMCs for several binary mixtures of linear surfactants, thereby laying the foundation for using the CSMT model to predict micellization properties of mixtures of surfactants that have a more complex chemical architecture. Finally, an MT framework was also developed to predict the micellization properties of mixtures of fluorocarbon-based and hydrocarbon-based surfactants. This mixing reduces the use of fluorinated surfactants in the surfactant formulation, thereby addressing the non-biodegradability and toxicity concerns associated with fluorinated surfactants. An enthalpy of mixing contribution resulting from the interactions between the fluorocarbon tails and the hydrocarbon tails, estimated using the Regular Solution Theory, was included in the MT framework. The ability of the MT framework to predict the coexistence of two types of mixed micelles in solution was demonstrated. The MT framework predictions of micelle population distributions, CMCs, and optimal micelle compositions were compared with the experimental values for various mixtures of fluorocarbon-based and hydrocarbon-based surfactants. The models developed in this thesis provide a molecular level understanding of the micellization behavior of fluorocarbon-based surfactants and their mixtures. The models are able to predict several important micellization properties of surfactants and their mixtures that can guide surfactant formulators in the synthesis, characterization, design, and optimization of surfactant formulations that exhibit desirable properties.
Author: Raymond C. Rowe
Publisher: Amer Pharmacists Assn
ISBN: 9781582121352
Category : Medical
Languages : en
Pages : 888
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Book Description
An internationally acclaimed reference work recognized as one of the most authoritative and comprehensive sources of information on excipients used in pharmaceutical formulation with this new edition providing 340 excipient monographs. Incorporates information on the uses, and chemical and physical properties of excipients systematically collated from a variety of international sources including: pharmacopeias, patents, primary and secondary literature, websites, and manufacturers' data; extensive data provided on the applications, licensing, and safety of excipients; comprehensively cross-referenced and indexed, with many additional excipients described as related substances and an international supplier's directory and detailed information on trade names and specific grades or types of excipients commercially available.
Author: CLAUDE. BOUILLON
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: International Atomic Energy Agency
Publisher:
ISBN:
Category : Business & Economics
Languages : en
Pages : 374
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Author: Arthur A. Tracton
Publisher: CRC Press
ISBN: 1420027328
Category : Mathematics
Languages : en
Pages : 930
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Book Description
Serving as an all-in-one guide to the entire field of coatings technology, this encyclopedic reference covers a diverse range of topics-including basic concepts, coating types, materials, processes, testing and applications-summarizing both the latest developments and standard coatings methods. Take advantage of the insights and experience of over
Author: Peter A. Williams
Publisher: John Wiley & Sons
ISBN: 0470994193
Category : Technology & Engineering
Languages : en
Pages : 344
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Book Description
Natural and synthetic water soluble polymers are used in a wide range of familiar industrial and consumer products, including coatings and inks, papers, adhesives, cosmetics and personal care products. They perform a variety of functions without which these products would be significantly more expensive, less effective or both. Written for research, development and formulation chemists, technologists and engineers at graduate level and beyond in the fine and specialty chemicals, polymers, food and pharmaceutical industries, the Handbook of Industrial Water Soluble Polymers deals specifically with the functional properties of both natural and synthetic water soluble polymers. By taking a function based approach, rather than a “polymer specific” approach the book illustrates how polymer structure leads to effect, and shows how different polymer types can be employed to achieve appropriate product properties.
Author: Joel K. Swadesh
Publisher: CRC Press
ISBN: 1420042661
Category : Science
Languages : en
Pages : 480
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Book Description
Product specifications, regulatory constraints, and tight production schedules impose considerable pressures on separation scientists in industry. The first edition of HPLC: Practical and Industrial Applications helped eliminate the need for extensive library or laboratory research when confronting a problem, an unfamiliar technique, or work in a n
Author: Mark J. Jackson
Publisher: Springer
ISBN: 3319671324
Category : Technology & Engineering
Languages : en
Pages : 566
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Book Description
This book is a comprehensive treatment of micro and nanofabrication techniques, and applies established and research laboratory manufacturing techniques to a wide variety of materials. It is a companion volume to “Micro and Nanomanufacturing” (2007) and covers new topics such as aligned nanowire growth, molecular dynamics simulation of nanomaterials, atomic force microscopy for microbial cell surfaces, 3D printing of pharmaceuticals, microvascular coaptation methods, and more. The chapters also cover a wide variety of applications in areas such as surgery, auto components, living cell detection, dentistry, nanoparticles in medicine, and aerospace components. This is an ideal text for professionals working in the field, and for graduate students in micro and nanomanufacturing courses.
