Download or read book On the Adhesive Properties of Polyelectrolyte Multilayers written by Erik Johansson and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of polyelectrolyte multilayers (PEMs) by the consecutive treatment of a charged substrate with cationic and anionic polyelectrlytes is an effective method for assigning new or improved surface properties to a substrate. The potential of PEMs for increasing the adhesive interaction between substrates was explored in this thesis in order to determine the molecular mechanisms responsible for the improvement in adhesion. In addition, the objective was to investigate whether there is a relationship between the structural and viscoelastic porperties of the multilayers and their adhesive porperties. PEMs formed from polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) were studied using atomic force microscopy (AFM) and the surface force apparatus (SFA). AFM colloidal probe pull-off force measurements, conducted under wet conditions, showed that the adhesive interactions werre higher when PAH was absorbed in the outermost layer than when PAA capped the PEM. The results also show that the adhesion increased with time in contact at maximum load. A low molecular weight combination of polyelectrolytes resulted in higher pull-off forces than did a high molecular weight combinaison. These results suggest that the development of a strong adhesive joint is very dependent on the mobility of the polyelectrolytes and interdiffusion across the interface. SFA measurements were conducted under dry conditions, at 100%RH, and under wet conditions. Under dry conditions, the adhesive forces between two mica sheets was decreased after they were covered by PEMs, indicating that the adhesive interaction was dominated by the thermodynamic work od adhesion between the two surfaces. Measurements using a combinaison of stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation( QCM-D) show that PEMs can be successfully constructed from cationic starch and anionic starch at electrolyte conentrations of 1 and 10 mM NaCl. (...).

Download or read book Adhesive Properties of Wet Polyelectrolyte Multilayer Films and Electrophoretic Deposition of Polyelectrolyte Complexes written by Chao Li and published by . This book was released on 2016 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Investigating the Adhesive Strength and Morphology of Polyelectrolyte Multilayers by Atomic Force Microscopy written by Sena Ada and published by . This book was released on 2008 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Polyelectrolyte multilayer (PEM) thin films prepared via the Layer-by-Layer (LbL) deposition technique are of special interest in this research. The purpose of this study is to replace current mechanical closure systems, based on hook-and-loop type fasteners (i.e. Velcro), with PEM thin film systems. The technique is simple, cheap, versatile and environmental friendly; as a consequence a variety of thin films can be easily fabricated. By proposing PEMs as non-mechanical and nanoscopic molecular closures, we aim to obtain hermetic sealing, good adhesive strength, and peel off ease. Atomic force microscopy (AFM) and colloidal probe techniques were used to characterize the morphology, roughness and adhesive properties of PEMs. AFM measurements were conducted in air, necessarily requiring careful control of ambient humidity. PEMs were formed by consecutive deposition of polyanions and polycations on a charged polyethylene terephthalate (PET) solid surface, the result of which was stable nanostructured films. By systemically varying the parameters of PEM build-up process: different combinations of polyelectrolytes, different numbers of bilayers (polyanion/polycation pairs), and miscellaneous types and concentrations of salts (NaCl, NaBr and NaF salts at 0.5 M and 1.0 M concentrations), the adhesion and morphology of PEMs were thoroughly investigated. The PEM thin films specifically investigated include poly(ethyleneimine) (PEI), poly(styrene sulfonate) (PSS), poly(allylamine hydrochloride) (PAH), poly(acrylic acid) (PAA), and poly(diallydimethylammonium chloride) (PDADMAC). Silica colloidal probes were utilized in the investigation, some of which were functionalized with COOH and/or coated with PEI-PSS. Silica colloidal probes were used in order to quantify interaction forces on the PEMs. A functionalized silica colloidal probe (a probe with COOH surface chemistry) and a silica colloidal probe coated with PEI-PSS were used to simulate PEM-PEM interactions. The results suggest that adhesion in the PEMs depend on the number of layers, the salt concentration and the salt type used during the build-up process, the environmental conditions where the adhesion force measurements were made, and the choice of probe.

Download or read book Glycopolymers Polyelectrolyte Multilayers for Biomedical Applications written by and published by Scholar Press. This book was released on 2018-01-16 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The theoretical background of this work is concerning with the drug loaded polyelectrolyte multilayers (PEM) modified by the host-guest interaction of biocompatible hyperbranched core-shell glycopolymers. The glycopolymer in this work is the hyperbranched polyethyleneimine that was modified with maltose moieties using reductive amination. Thus, the use of glycohyperbranched polymers for drug delivery would allow the avoid naturally occurring drug resistance due to decreased transporter activity. Concerning preparative method, PEM was fabricated using layer-by-layer (LbL) processes involve the sequential deposition of two polyions that physically bond together. Control was taken on the stoichiometric ratio related to cationic and anionic repeating units, which was chosen close to zero for the final applied PEM. Concerning analytical methods, a couple of physical-chemical methods were applied to characterize colloid stability, adhesiveness, drug loading and release of fabricated PEM. In conclusion, a highly sable and sustainable PEM coats on a surface of an activated solid substrate has been fabricated with an efficient ability to recycle the charged molecule for more than 24 times.

Download or read book On the Adhesion Between Substrates Covered with Polyelectrolyte Multilayers written by Rikard Lingström and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines the formation of Polyelectrolyte Multilayers (PEM) on cellulose fibres as a new way of influencing the fibre surface and the adhesion between wood fibres. The aim of the study was to enhance the fundamental understanding of the adsorption mechanisms behind the formation of Polyelectrolyte Multilayers on cellulose fibres; to study how the properties of the layers can be influenced and to show how the properties of the layers influence the adhesion between the fibres and the strength of paper sheets made from the PEM treated fibres. Different polyelectrolyte systems are known to form PEMs with different properties, and in this work two different polymer systems were extensively studied: poly(dimethyldiallylammonium chloride) (PDADMAC) / poly(styrene sulphonate) (PSS), which are both strong polylectrolytes (i.e. are highly charged over a wide range of pH) and poly allylaminehydrochloride (PAH) /poly acrylic acid (PAA), which are both weak polyelectorlytes (i.e. sensitive to pH changes). PEMs were also formed from PAH/ poly(3,4-ethylenedioxythiophene):PSS (PEDOT:PSS), in order to form electrically conducting PEMs on fibres and PEM-like structures were formed from polyethylene oxide (PEO) and polyacrylic acid (PAA). (...).

Download or read book Handbook of Polyelectrolytes and Their Applications Polyelectrolyte based multilayers self assemblies and nanostructures written by Sukant K. Tripathy and published by . This book was released on 2002 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Swelling and Contraction Properties for Polyelectrolyte Multilayers and Polymer Thin Films Measured by In situ Ellipsometry written by Yubing Ma and published by . This book was released on 2016 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Tailoring Fibre and Paper Properties Using Physical Adsorption of Polyelectrolytes written by and published by . This book was released on 2012 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multilayer Thin Films written by Gero Decher and published by John Wiley & Sons. This book was released on 2012-06-11 with total page 1157 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second, comprehensive edition of the pioneering book in this fi eld has been completely revised and extended, now stretching to two volumes. The result is a comprehensive summary of layer-by-layer assembled, truly hybrid nanomaterials and thin fi lms, covering organic, inorganic, colloidal, macromolecular, and biological components, as well as the assembly of nanoscale fi lms derived from them on surfaces. These two volumes are essential for anyone working in the field, as well as scientists and researchers active in materials development, who needs the key knowledge provided herein for linking the field of molecular self-assembly with the bio- and materials sciences.

Download or read book Layer by Layer Films for Biomedical Applications written by Catherine Picart and published by John Wiley & Sons. This book was released on 2015-01-30 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt: The layer-by-layer (LbL) deposition technique is a versatile approach for preparing nanoscale multimaterial films: the fabrication of multicomposite films by the LbL procedure allows the combination of literally hundreds of different materials with nanometer thickness in a single device to obtain novel or superior performance. In the last 15 years the LbL technique has seen considerable developments and has now reached a point where it is beginning to find applications in bioengineering and biomedical engineering. The book gives a thorough overview of applications of the LbL technique in the context of bioengineering and biomedical engineering where the last years have witnessed tremendous progress. The first part familiarizes the reader with the specifics of cell-film interactions that need to be taken into account for successful application of the LbL method in biological environments. The second part focuses on LbL-derived small drug delivery systems and antibacterial agents, and the third part covers nano- and microcapsules as drug carriers and biosensors. The fourth and last part focuses on larger-scale biomedical applications of the LbL method such as engineered tissues and implant coatings.

Download or read book Polyelectrolytes written by Visakh P. M. and published by Springer. This book was released on 2014-09-03 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a valuable reference source to graduate and post graduate students, engineering students, research scholars polymer engineers from industry. The book provides the reader with current developments of theoretical models describing the thermodynamics polyelectrolytes as well as experimental findings. A particular emphasis is put on the rheological description of polyelectrolyte solutions and hydrogels.

Download or read book Handbook Of Green Materials Processing Technologies Properties And Applications In 4 Volumes written by Kristiina Oksman and published by World Scientific. This book was released on 2014-04-11 with total page 1124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Green materials and green nanotechnology have gained widespread interest over the last 15 years; first in academia, then in related industries in the last few years.The Handbook of Green Materials serves as reference literature for undergraduates and graduates studying materials science and engineering, composite materials, chemical engineering, bioengineering and materials physics; and for researchers, professional engineers and consultants from polymer or forest industries who encounter biobased nanomaterials, bionanocomposites, self- and direct-assembled nanostructures and green composite materials in their lines of work.This four-volume set contains material ranging from basic, background information on the fields discussed, to reports on the latest research and industrial activities, and finally the works by contributing authors who are prominent experts of the subjects they address in this set.The four volumes comprise of:The first volume explains the structure of cellulose; different sources of raw material; the isolation/separation processes of nanomaterials from different material sources; and properties and characteristics of cellulose nanofibers and nanocrystals (starch nanomaterials). Information on the different characterization methods and the most important properties of biobased nanomaterials are also covered. The industrial point of view regarding both the processability and access of these nanomaterials, as well as large scale manufacturing and their industrial application is discussed — particularly in relation to the case of the paper industry.The second volume expounds on different bionanocomposites based on cellulose nanofibers or nanocrystals and their preparation/manufacturing processes. It also provides information on different characterization methods and the most important properties of bionanocomposites, as well as techniques of modeling the mechanical properties of nanocomposites. This volume presents the industrial point of view regarding large scale manufacturing and their applications from the perspective of their medical uses in printed electronics and in adhesives.The third volume deals with the ability of bionanomaterials to self-assemble in either liquids or forming organized solid materials. The chemistry of cellulose nanomaterials and chemical modifications as well as different assembling techniques and used characterization methods, and the most important properties which can be achieved by self-assembly, are described. The chapters, for example, discuss subjects such as ultra-light biobased aerogels based on cellulose and chitin, thin films suitable as barrier layers, self-sensing nanomaterials, and membranes for water purification.The fourth volume reviews green composite materials — including green raw materials — such as biobased carbon fibers, regenerated cellulose fibers and thermoplastic and thermoset polymers (e.g. PLA, bio-based polyolefines, polysaccharide polymers, natural rubber, bio-based polyurethane, lignin polymer, and furfurylalchohol). The most important composite processing technologies are described, including: prepregs of green composites, compounding, liquid composite molding, foaming, and compression molding. Industrial applications, especially for green transportation and the electronics industry, are also described.This four-volume set is a must-have for anyone keen to acquire knowledge on novel bionanomaterials — including structure-property correlations, isolation and purification processes of nanofibers and nanocrystals, their important characteristics, processing technologies, industrial up-scaling and suitable industry applications. The handbook is a useful reference not only for teaching activities but also for researchers who are working in this field.

Download or read book Polyelectrolyte Multilayers of Cationic and Anionic Starch and Their Use for Improving the Strength of Papers Made from Mechanical Pulps written by Lisa Lundström and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Graphic paper is experiencing severe competition from other materials and, most of all, from other media. This means there is a great need to improve paper quality while reducing raw material and production costs. Polyelectrolyte multilayer (PEM) treatment (i.e., consecutively adding cationic and anionic polyelectrolytes to the charged surface of wood fibres and fines, to form layers of these polyelectrolytes on the fibres/fines) has in recent years been found to offer great potential both to introduce new properties and to improve the mechanical properties of papers made of the treated fibres.The main objective of this thesis was to develop a strategy for the PEM treatment of cationic and anionic starch to improve the mechanical properties of paper made of thermomechanical pulp (TMP), since PEM treatment of fibres has displayed great potential to improve the mechanical properties of sheets made of chemical pulp. Mechanical pulp, however, has a large fine material content. Since the fine material is highly charged, polyelectrolyte consumption would be unacceptably high if the entire pulp were PEM treated, so we applied PEM treatment only to a fibre fraction of the pulps in most trials in the present work. The polyelectrolytes used for PEMs have so far mostly been well-defined, expensive ones unsuitable for use in standard paper grades; to develop a more economically realistic alternative, we used cationic and anionic starches.PEM formation on SiO2 surfaces from three differently charged cationic and anionic starches was first evaluated at three different salt levels using quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The starch combinations displaying the highest potential for stable PEM formation at higher salt concentrations were then evaluated on an entire TMP pulp, as well as on a fraction of the pulp to reduce the amount of starch needed for PEM formation.The results indicate that it is possible to form PEMs from cationic and anionic starch on a SiO2 surface. The charge density, salt concentration, and combination of starches all influenced PEM formation. PEM formation on mechanical fibres produced large improvements in the mechanical properties of the sheets made of the treated fibres, and the tensile index, stretch-at-break, Z-strength, and Scott bond values all increased. Fractionating the pulp and PEM treating only a fraction of the pulp, the long fibre and middle fraction, produced large decreases in the amount of starch needed and large improvements in the mechanical properties of the sheets when no fine material was subsequently added. As untreated fine material was subsequently added, the improvement in mechanical properties decreased. PEM formation produced almost no reduction in formation and only a slight increase in sheet density.

Download or read book Advance in Tribology Study of Polyelectrolyte Multilayers written by Yanbao Guo and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This review introduced the preparation and structural characterization of polyelectrolyte multilayers in recent years and also summarized the tribology research progress of the polyelectrolyte multilayers, including tribological properties, surface adhesion characteristics, and wear resistance properties. Statistics analysis indicated that nanoparticles-doped polyelectrolyte multilayers present better friction and wear performance than pristine polyelectrolyte multilayers. Furthermore, the in situ growth method resulted in improved structural order of nanoparticles composite molecular deposition film. In situ nanoparticles not only reduced the molecular deposition film surface adhesion force and friction force but also significantly improved the life of wear resistance. That was due to the nanoparticles that possessed a good load-carrying capacity and reduced the mobility of the polymer-chain segments, which can undergo reversible shear deformation. Based on this, further research direction of in situ nanoparticles molecular deposition film was proposed.

Download or read book Scanning Probe Microscopy of Soft Matter written by Vladimir V. Tsukruk and published by John Wiley & Sons. This book was released on 2012-01-09 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: Well-structured and adopting a pedagogical approach, this self-contained monograph covers the fundamentals of scanning probe microscopy, showing how to use the techniques for investigating physical and chemical properties on the nanoscale and how they can be used for a wide range of soft materials. It concludes with a section on the latest techniques in nanomanipulation and patterning. This first book to focus on the applications is a must-have for both newcomers and established researchers using scanning probe microscopy in soft matter research. From the contents: * Atomic Force Microscopy and Other Advanced Imaging Modes * Probing of Mechanical, Thermal Chemical and Electrical Properties * Amorphous, Poorly Ordered and Organized Polymeric Materials * Langmuir-Blodgett and Layer-by-Layer Structures * Multi-Component Polymer Systems and Fibers * Colloids and Microcapsules * Biomaterials and Biological Structures * Nanolithography with Intrusive AFM Tipand Dip-Pen Nanolithography * Microcantilever-Based Sensors

Download or read book Chitin in Nature and Technology written by G.W. Gooday and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exegi monumentum ael'e perennius. The monument I have built will last longer than bronze. Horace My previous book, "Chitin", (1977) was listed by the publisher, as a "key research book", among the most requested books by libraries. It received favorable comments from. each of the journals which reviewed it, Science, 198, 28 Oct. 1977, Physiological Entomology, 2(4), Dec. 1977, The Canadian Institute of Food Science and Technology Journal, April 1978, The Quarterly Review of Biology, 53:361, 1978, Oceanographic Abstracts, 15:182, 1979, Annales de Zoologie-Ecologie Animale, 11:127, 1979, and Enzyme & Microbial Technology, 2, 1980. The variety of these journals testifies to the interdisci plinary character of chitin studies. "Chitin" has really been a landmark, to use the definition given by Science, because it stimulated interest in the less known polysaccharides and in modified chitins, besides chitin itself, to the point that three International Conferences on Chitin / Chitosan were convened (Boston, U. S. A. 1977, Sapporo, Japan 1982 and Senigallia, Italy 1985). In convening the 3rd International Conference on Chitin / Chitosan (1-4 April 1985), one of the main objectives was the preparation of the present book. While the proceedings of the previous two Conferences were very valuable, they did not appear in any book catalogs and this severely Ii mi ted their distribution.

Download or read book Formation and Properties of Polyelectrolyte Multilayers on Wood Fibres written by Rikard Lingström and published by . This book was released on 2006 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: