Author: Michael Frederick Durstock
Publisher:
ISBN:
Category :
Languages : en
Pages : 248

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Author: Gero Decher
Publisher: John Wiley & Sons
ISBN: 352760541X
Category : Technology & Engineering
Languages : en
Pages : 543

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Materials scientists are often faced with the problem of modifying surfaces of objects, yet keeping their shape and properties. This book provides a detailed survey on the new technology of adsorption from solution for the fabrication of molecularly ordered multicomposite films in order to replace and expand on the well known Langmuir-Blodgett technology and to open the field of molecular self-assembly to materials and biosciences. The book is aimed at scientists who want to integrate several different functional entities in a single device. To this audience it presents the technique of layer-by-layer assembly as today's most powerful key technology, which is low cost, solution based and very robust. It is already beginning to make the transition from academic research into industrial mass production.

Author: Yubing Ma
Publisher:
ISBN:
Category : Hydrogen bonding
Languages : en
Pages : 77

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Weak polyelectrolyte multilayers (PEMs) fabricated by the Layer by Layer (LBL) assembling technique showed special swollen and contraction behaviors when they came in contact with water and organic liquids. The contraction responses of PEM were found to be dependent on the solvent selection. The correlation between the degrees of the films contraction and the solvent type needed be explored. Therefore, in this study, we utilized solubility parameters to discuss the responses for branched poly (ethylene imine)/poly (acrylic acid) (BPEI/PAA) multilayers when soaked in a variety of solvent liquids. When immersed in organic solvents, film dehydrated and contraction also caused mechanical property changes for BPEI/PAA films. The film's thickness was the best predictor for determining how a film swelled in water or contracted in organic liquid. The hydrogen bonding ability of the solvents played an important role in determining the degree of film contraction in most cases, for these solvents, it did so when increasing the temperature of the measurement corresponding to reducing the strength of the hydrogen bonding, and decreasing the ability to dehydrate the films as well. However, some solvents did not follow the linear trend with the strength of hydrogen bonding; in these, a stronger correlation was observed between contraction degrees and dielectric constants, showing that traditional solvent quality discussions and electrostatics were significant to understanding the contraction behavior of PEMs in organic solvents. Besides the PEM system, the swelling behavior of poly(n-propyl methacrylate), PPMA, films in water were also measured in-situ using spectroscopic ellipsometry. Two different end groups grafted poly (n-propyl methacrylate)s with similar high molecular weight were successfully synthesized by the reversible addition-fragmentation chain-transfer polymerization (RAFT) synthesis method. The end group of the two PPMAs impacted the swelling behavior over the temperature range of 25 to 50 0C At 25 0C, the dithiobenzoate terminated PPMA (PPMA-DB) leading to significantly less swelling (4.2 vol%) than the dodecylsulfanylthiocarbonyl terminated PPMA (PPMA-DD, 6.4 vol%). These PPMA films swelled significantly more than one would expect since their hydrophobicity, which was attributed to the other end group from RAFT being a carboxylic acid in both polymers. As the temperature was increased, the swelling for the PPMA-DB increased; the swelling decreased for the PPMA-DD with a crossover at approximately 350C Both the swelling processes had two stages: an initial rapid swelling within the first minute and then a slow increase in thickness over several hours. The different swelling trends of the PPMA-DB and PPMA-DD described the end group effect on the polymers especially the chain conformations. Additionally, for the mechanical properties of these two kinds of PPMA, the elastic modulus was similar; however, the fracture modulus showed some difference, in that the larger swelling PPMA-DD films have a somewhat smaller fracture strength also influenced by the different end groups.

Author: Sze Yinn Jessie Wong
Publisher:
ISBN:
Category :
Languages : en
Pages : 160

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This thesis work focuses on designing thin polyelectrolyte multilayer (PEM) films via layer-bylayer (LbL) deposition technique with the ability to kill pathogenic bacteria and inactivate human viruses, especially the influenza (flu) virus on contact. This work builds on four years of research at the Institute for Soldier Nanotechnologies (ISN) focusing on creating new, nonleaching microbicidal material; this film is envisioned to be used as permanent surface coatings for weapons, equipments, uniforms, personal items, etc. because a small reduction in the rate of infection will greatly enhance the readiness and performance of soldiers and other military personnel. Extending this application to everyday life, commonly handled objects such as doorknobs, computer keyboards, and touch screens can also be made sterile by coating them with these highly effective microbicidal PEM films. These films can also be used to prevent infections and long-term bacterial biofilms on implant surfaces. The ultimate aim of this thesis work is to create a broadly applicable multifunctional platform film technology that will satisfy various thin film surface coating applications; this film will impart a surface with long term antimicrobial / antifouling functionality via a permanent microbicidal base, and controlled delivery of a therapeutic agent via a hydrolytically degradable top film as needed. Efforts were focused on maximizing and understanding the factors that influence the microbicidal / antifouling property of the film; thus far, we successfully designed a set of contact-killing ionically cross-linked polymeric thin films; a hydrophobic polycation, linear NNdodecyl, methyl- poly(ethylenimine) (DMLPEI) with microbicidal activity was layered with a hydrophilic polyanion, such as poly(acrylic acid) (PAA), to create LbL films highly effective against Escherichia coli and Staphylococcus aureus (Gram negative and positive bacteria, respectively), as well as the influenza A/WSN (H1N1) virus. The microbicidal film was also demonstrated to significantly resist adsorption of protein from blood plasma relative to an uncoated substrate. By generating PEM films assembled with the hydrophobic N-alkylated poly(ethylenimine) and the hydrophilic poly(acrylic acid), an ultrathin film that exhibited antifouling and antimicrobial properties was created. Results showed that a fine balance of hydrophobicity and hydrophilicity on the surface of the films was needed to create molecularlevel heterogeneities unfavorable to protein adsorption; due to the contrasting nature of the polymer making up the film, nanoscale segregation of the polymer segments into hydrophobic and hydrophilic moieties could occur on the surface. We then moved on to design a dual functional LbL film construct combining the permanent microbicidal / antifouling base film with a hydrolytically degradable PEM top film offering controlled and localized delivery of therapeutics (e.g. antibiotic, anti-inflammatory drug, etc.). When the degradable top film is completely eroded, the surface will be left with the permanent microbicidal film for long-term prevention of fouling by biomolecules and microorganisms (e.g., proteins and bacteria).

Author: Rajaram S. Mane
Publisher: Elsevier
ISBN: 0323853323
Category : Technology & Engineering
Languages : en
Pages : 448

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Book Description
Solution Methods for Metal Oxide Nanostructures reviews solution processes that are used for synthesizing 1D, 2D and 3D metal oxide nanostructures in either thin film or in powder form for various applications. Wet-chemical synthesis methods deal with chemical reactions in the solution phase using precursors at proper experimental conditions. Wet-chemical synthesis routes offer a high degree of controllability and reproducibility for 2D nanomaterial fabrication. Solvothermal synthesis, template synthesis, self-assembly, oriented attachment, hot-injection, and interface-mediated synthesis are the main wet-chemical synthesis routes for 2D nanomaterials. Solution Methods for Metal Oxide Nanostructures also addresses the thin film deposition metal oxides nanostructures, which plays a very important role in many areas of chemistry, physics and materials science.Each chapter includes information on a key solution method and their application in the design of metal oxide nanostructured materials with optimized properties for important applications. The pros and cons of the solution method and their significance and future scope is also discussed in each chapter. Readers are provided with the fundamental understanding of the key concepts of solution synthesis methods for fabricating materials and the information needed to help them select the appropriate method for the desired application. Reviews the most relevant wet chemical solution methods for metal oxide nanostructures, including sol-gel, solvothermal, hydrothermal, co-precipitation methods, and more Addresses thin film deposition techniques for metal oxide nanostructures, such as spray-pyrolysis, electrodeposition, spin coating and self-assembly Discusses the pros and cons of each solution method and its significance and future opportunities

Author:
Publisher:
ISBN:
Category : Electrooptics
Languages : en
Pages : 434

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Author: Adam John Nolte
Publisher:
ISBN:
Category :
Languages : en
Pages : 225

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Polyelectrolyte multilayers (PEMs) are a versatile type of thin film that is created via layer-by-layer assembly of positively and negatively charged polymers from aqueous solutions. Precise control of the PEM thickness, chemical functionality, and molecular architecture is made possible by changing the polyelectrolytes and assembly conditions during film growth, allowing films to be designed with properties suitable for a given application. This thesis elucidates the intra-film structure and interactions of PEMs through the use of optical, mechanical, and chemical techniques. PEM rugate filters, wherein the refractive index varies through the depth of the film in a continuous, periodic fashion, were constructed by confining silver nanoparticle growth to layers of nanometer-scale thickness. The ability to construct such structures is shown to be dependent on the ability to precisely control the concentration of metal-binding carboxylic acid groups throughout the depth of the film. Software to enable the computation design and optical simulation of these and similar structures was developed.

Author: Chao Li
Publisher:
ISBN:
Category : Polyelectrolytes
Languages : en
Pages : 82

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Weak polyelectrolyte multilayers prepared by using layer-by-layer (LbL) technique are known to become sticky upon contact with water and behave as a viscoelastic fluid, but the full extent of this wet adhesive property is not fully understood. In this study, the wet adhesive performance of polyelectrolyte multilayers consisting of branched poly(ethylene imine) and poly(acrylic acid) under controlled conditions was investigated by using a 90° peel test. The peel force is highest under neutral condition, and it decreases in acidic/basic environment. The addition of metal ions changes the peel force, either increasing it or decreasing it based on the nature of the metal ion. Addition of Cu2+ stiffens multilayers, preventing multilayers from acting as an effective wet adhesive. The films are also characterized with zeta potential and shear rheometry, and the adhesiveness can be recovered by rewetting for at least 5 times. This polyelectrolyte based wet adhesive can be adhered to soft, wet surfaces like biological tissues such as liver. These multilayer films in this work show wet adhesive properties, however, the layer by layer technique used to fabricate these films requires several steps and take a long time. Therefore, new methods are needed to make these thin films. Spin-assisted LbL assembly, spray-assisted LbL assembly and electric field-assisted LbL assembly are widely studied because they are simple and time-saving. Electric field-assisted LbL assembly has been gaining an increasing interest. One option for realizing this may be the electrophoretic deposition of weak polyelectrolyte complexes, made by mixing polyelectrolytes of opposite charge together, has not been studied yet. Therefore, electrodeposition of polyelectrolyte complexes under different conditions (i.e. pH, ratio of polycation and polyanion, concentration of polyelectrolyte complexes, concentration of salt and type of electric field) was investigated in this work. Polyelectrolyte complexes at moderate pH values and at the ratio of polycation and polyanion at 20 shows highest electrophoretic mobility. The thickness of polyelectrolyte complex film decreases with decreasing the concentration of polyelectrolyte complexes while the thickness increases when a proper amount of salt is added during preparing polyelectrolyte complexes. Under controlling pulse current at 10mA, a thicker film can be achieved but the surface is rougher compared with one prepared by using pulse potential at 10V. This work provides insight into both the wet adhesive properties of polyelectrolyte multilayers and electrophoretic deposition of polyelectrolyte complexes.

Author: John R. Reynolds
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 992

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This book shows that research involving electrical, optical and magnetic properties of organic solid-state materials continues to grow both in scope and technological importance. Early studies of charge transport in conducting polymers have evolved from the elucidation of fundamental structure/function relationships to applications such as batteries, simple electrical devices such as diodes, chemical sensors, antistatic coatings, microwave and millimeter wave-absorbing materials, and photochromic devices. A particularly exciting evolution has been the discovery and development of organic light-emitting diodes (OLEDs) which appear to be nearing commercialization in an amazingly short period of time. This application is of particular interest because both electrical and optical properties must be considered.. Topics include: organic light-emitting materials and devices; photonic materials and devices; conducting and electroactive polymers and materials; molecular and supramolecular engineering; organic metals and magnetic materials and poster presentations.

Author:
Publisher:
ISBN:
Category : Organic compounds
Languages : en
Pages : 992

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