Download or read book The Effect of Solute Concentration on the Equilibrium Partitioning and Hindered Gradient Diffusion of Colloids in Polymeric Hydrogels written by Kristan Kay-Schurle Buck and published by . This book was released on 2000 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2001 with total page 834 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Partitioning and Transport in Complex Nano structured Systems written by Nathan Winter Lloyd and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With the overall goal of advancing nano-scale encapsulation technology, two companion problems in the controlled release of small hydrophobic molecules have been studied: equilibrium partitioning and colloidal transport, each within nano-structured matrices. In the first research focus, a solid phase microextraction (SPME) method was developed to measure air-water-surfactant micelle partitioning of hydrophobic analytes. Vapor-liquid partitioning (Kv̳l̳) measurements were performed independently in the headspace (HS-SPME) and via direct immersion in the liquid (DI-SPME), and the results were compared. The method involves varying the total amount of analyte as well as the ratio of vapor to liquid in the closed, static system, such that the need for an external calibration is eliminated. The compounds studied cover four orders of magnitude in Kv̳l̳, and agreement between DI-SPME and HS-SPME results was good, showing that these two methods were capable of providing accurate, complementary measurements. Equilibrium partitioning of limonene to sodium dodecyl sulfate (SDS) micelles was also measured using HS-SPME by varying the concentration of SDS. By fitting the data to a simple model, the cmc was accurately measured and the micelle-liquid partition coefficient was determined. In the second research focus, the diffusion of SDS in solution and in agarose gel was measured and compared with an a priori model for colloidal transport which invokes hydrodynamic and statistical thermodynamic arguments to account for micelle-micelle and micelle-gel fiber interactions. Experimental results show that the concentration effect is enhanced considerably by the strong charge associated with SDS micelles. At high ionic strength, this concentration effect is further enhanced in 1% agarose gel, but in 2% gel the trend reverses, strongly suggesting a decrease in the micellar aggregation number. At low ionic strength, a concentration effect with a pronounced second order dependence is evident. Results show that the diffusion coefficient does not change appreciably with gel concentration up to 2%, and theoretical analysis suggests that this is due to partial canceling between the effects of solute-gel and solute-solute interactions. The pronounced second-order dependence is explained qualitatively by the changing Debye length and its influence on the thermodynamic driving force.
Download or read book Transport in Complex Self assembled Surfactant Systems written by Wyatt Jacob Musnicki and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this work is to advance the understanding of the diffusive transport of hydrophobic compounds (pharmaceuticals, nutraceuticals, flavors, pesticides, etc.) solubilized in microemulsions and the particles that carry them through solution and in fibrous media. The first focus of this research was to investigate the gradient-diffusion of charged anionic micelles in solution and a fibrous gel at moderate but dilute concentrations above the critical micelle concentration. Of particular interest were the effects of micelle, gel, and sodium chloride concentration on the micelle diffusivity. Holographic interferometry was used extensively to measure the micelle gradient-diffusion coefficient as a function of surfactant concentration at multiple sodium chloride and gel concentrations. The micelle diffusivity was shown to increase linearly with surfactant concentration at the two larger sodium chloride concentrations and all gel concentrations. In general, the strength of this effect increased with decreasing sodium chloride concentration and increased with gel concentration. This behavior is evidence of decreasing micelle-micelle electrostatic interactions with increasing sodium chloride concentrations, and increasing excluded volume effects and hydrodynamic screening with increasing gel concentration, respectively. The extrapolated, infinite-dilution diffusion coefficients and the rate at which the micelle diffusivity increased with surfactant concentration were compared with predictions of previously published theories in which the micelles are treated as charged, colloidal spheres and the gel as a Brinkman medium. The experimental data and theoretical predictions were in good agreement, particularly at the higher salt concentrations. The second focus of this work was to investigate the gradient-diffusion of hydrophobic compounds in microemulsions. Three solutes of increasing hydrophobicity were used and two different types of surfactants, one non-ionic and the other anionic, were investigated. The transport of the hydrophobic compounds within the microemulsions were tracked using holographic interferometry. For three of the solute-surfactant pairs, the measured interferometry patterns exhibited pseudo-binary features and the effective binary diffusion coefficient of the solutes was extracted from these patterns. The effective diffusion coefficient of one solute-surfactant pair was between the slowest diffusing component, the micelle, and the fastest diffusing component, the solute in water. The other measured effective diffusivities were either much smaller than the micelle diffusivity or much larger than the solute's diffusivity in water. For the remaining three solute-surfactant pairs, the interferometric patterns clearly demonstrated the transport of more than two components. For these, the effective binary diffusion coefficients could not be extracted. To improve on the pseudo-binary results and to account for the coupled transport of solute, a ternary multicomponent method was adapted for use with holographic interferometry. The ternary diffusivities: D11, D12, D21, and D22 were determined for all sets of solutes and surfactants. The value of D22 were found to be in all cases equal to the micelle diffusivity. The values of D11 were found to be less than the solute's diffusivity in water and to decrease as the solute's hydrophobicity increased. The values of D12 and D21 were found to depend in a complex manner with the solute's hydrophobicity and the type of surfactant used. Holographic interferometry was a useful tool for extracting complex information from the transport mechanisms of the solute and surfactant gradient-diffusion in micelles and microemulsions.
Download or read book Polymer Migration Induced by Concentration Gradients of Salts Or Crowding Agents written by Michele Schultz McAfee and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Diffusion-based mass transfer plays an important role in many biological and industrial processes. Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism, which is not well understood, is known as cross-diffusion. For a ternary solution composed of polyethylene glycol (PEG, 1) and salt (2), the system can be described using two cross-diffusion coefficients. The first cross-diffusion coefficient, which characterizes polymer migration induced by the presence of a salt gradient, is denoted as polymer diffusiophoresis (D12). The other cross-diffusion coefficient, which characterizes salt diffusion induced by the presence of a polymer gradient, is denoted as salt osmotic diffusion (D21). Related diffusion experiments were performed by Rayleigh interferometry and dynamic light scattering (DLS) at 25oC. The first objective of this dissertation is to investigate the effect of polymer size (10, 20, 35, and 100 kg mol-1) on the two cross-diffusion mechanisms in the presence of aqueous KCl. We show that D21 remains approximately the same for all the investigated polymer sizes; however, D12 increases with PEG size. The second objective of this dissertation is to investigate D12 and D21 in ternary solutions containing PEG (20 kg mol-1) in the presence of different salt types. We divided the study into two different categories: salting-out (sulfate and chloride salts) and salting-in (thiocyanate salts) according to the Hofmeister series. We found that both D12 and D21 can be related to preferential hydration and hydration of the polymer. Furthermore, we developed a model that allows us to characterize salting-out strength from our D21 results. In the case of the thiocyanate salts, we developed another model to describe our D12 results. This model shows that our experimental results can be explained by considering polymer-anion binding. The final objective of this dissertation is to investigate the effect of cross-diffusion in a ternary aqueous polymer system in which the additive is large (crowding agent) compared to PEG. In this system, we employed the use of PEG (2 kg mol-1) and the crowding agent is tyloxapol micelles. Our results were explained in terms of excluded volume interactions and solute hydration"--Abstract.
Download or read book Effects of Plasma Proteins on the Sieving of Macromolecular Tracers in the Kidney written by Matthew J. Lazzara and published by . This book was released on 2003 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ultrafiltration of plasma in the mammalian glomerulus is the first step in the processing of blood by the kidney. Proper functioning of this process is critical to the kidney's ability to effectively eliminate waste and retain desirable substances. The glomerular barrier has long been regarded as both a size and charge selective screen for plasma solutes. The origin of this selectivity is found in the unique three-layered structure of the glomerular capillary wall (GCW), consisting of a fenestrated endothelium, the interdigitating foot processes of the glomerular epithelium, and the shared glomerular basement membrane (GBM). The selectivity properties of the GCW have commonly been probed by measuring the sieving coefficients of a variety of tracers, both proteins and exogenous polymers, across the intact glomerular barrier and across isolated components of the GCW. It was found previously that the sieving coefficients of the tracers Ficoll and Ficoll sulfate across isolated GBM were greatly elevated when BSA was present at physiological levels (Bolton et al. 1998). It was suggested that most of this increase was the result of steric interactions between BSA and the tracers which increased tracer partitioning from the bulk into the GBM. Such an effect, if present, would have important implications for the interpretation of macromolecular sieving studies, both in vivo and in vitro. The goals of this thesis research were to model the effect of an abundant protein on the partitioning of a dissimilar tracer molecule, to incorporate that effect into models for glomerular sieving, and to test the partitioning model by measuring the effect of protein concentration on the partitioning of protein and Ficoll in agarose gels. The theoretical effects of solute size on partition coefficients in straight pores or randomly oriented fiber matrices have been investigated previously for very dilute solutions, where solute-solute interactions are negligible, and also for more concentrated solutions consisting of spherical solutes of uniform size. For concentrated solutions it has been found that steric and other repulsive interactions among solutes increase the partition coefficient above the dilute limit. To extend the results for porous or fibrous media to include concentrated mixtures of solutes with different sizes or shapes, we used an excluded volume approach. In this formulation, which describes steric interactions only, partition coefficients were computed by summing all volumes excluded to a solute molecule by virtue of its finite size, the finite size of other solutes, and the presence of fixed obstacles (pore walls or fibers). For a mixture of two spherical solutes, the addition of any second solute at finite concentration increased the partition coefficient of the first solute. That increase was sensitive to the size of the second solute; for a given volume fraction of the second solute, the smaller its radius, the larger the effect. When the total volume fraction of solutes was fixed, an increase in the amount of a second, smaller solute increased the partition coefficient of the first solute, whereas an increase in the amount of a second, larger solute had the opposite effect. Results were obtained also for oblate or prolate spheroidal solutes and for fibrous media with multiple fiber radii. For constant total fiber volume fraction, an increase in the amount of a second, smaller fiber decreased the partition coefficient of a spherical solute, whereas an increase in the amount of a second, larger fiber had the opposite effect. Overall, the theory suggests that the introduction of heterogeneity, whether as mixtures of solute sizes or mixtures of fiber sizes, may cause partition coefficients to differ markedly from those of uniform systems. Using the excluded volume partitioning model, the theory for the sieving of macromolecular tracers was extended to account for the presence of a second, abundant solute. Using that theory, we returned to the experimental data of Bolton et al. (1998) and attempted to model the effect of protein concentration on Ficoll sieving. The osmotic reduction in filtrate velocity caused by an abundant, mostly retained solute will also tend to elevate the tracer sieving coefficient. The osmotic effect alone explained only about one third of the observed increase in the sieving coefficients of Ficoll and Ficoll sulfate, whereas the effect of BSA on tracer partitioning was sufficient to account for the remainder. At physiological concentrations, predictions for tracer sieving in the presence of BSA were found to be insensitive to the assumed shape of the protein (sphere or prolate spheroid). The effect of plasma proteins on tracer partitioning is expected to influence sieving not only in isolated GBM, but also in intact glomerular capillaries in vivo. To test the predicted effects of solute concentration on the equilibrium partitioning of single macromolecules and macromolecule mixtures, measurements of the equilibrium partition coefficients of BSA and four narrow fractions of Ficoll were made in agarose. Solutions of each test macromolecule were equilibrated with a known volume of gel, final liquid concentrations measured, and partition coefficients calculated by applying a material balance. The partition coefficient of each molecule was measured under dilute conditions and under conditions where BSA was present at concentrated levels. All measurements were made for two different gel solid volume fractions (4 and 6%). As expected, the partition coefficients decreased with increasing gel solid volume fraction and with increasing molecular size. Increasing BSA concentration caused an increase in the partitioning of BSA itself and that of all four sizes of Ficoll. This effect was most significant for the largest molecules. A subset of the measurements repeated at a higher ionic strength demonstrated that electrostatic interactions were unimportant. The experimental results were compared with predictions generated from the excluded volume partitioning theory. Agarose was represented as a randomly oriented array of cylindrical fibers, BSA was modeled as a prolate spheroid, and Ficoll was treated as a sphere. Comparisons of the theoretical predictions with the experimental data produced generally good agreement, indicating that steric interactions among solute molecules and between solute molecules and gel fibers could explain the partitioning behavior.
Download or read book Effect of Particle Size on the Destabilization of Colloidal Suspensions in Water written by Manuel R. Vilaret and published by . This book was released on 1965 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Poly ethylene Glycol written by J. Milton Harris and published by . This book was released on 1997 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume provides an interdisciplinary analysis of current biological applications of poly(ethylene glycol) (PEG). It includes a wide array of topics useful to materials scientists, organic chemists, biochemists, and bioengineers interested in drug delivery systems, pharmaceuticals and other biomaterials. The applications discussed include PEG-modified proteins, liposomes, drugs, surfaces of materials, and hydrogels. The volume also includes a review of PEG-oligonucleotides and a concise summary of the toxicology of PEG and its derivatives.
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 Polysaccharide Hydrogels written by Pietro Matricardi and published by CRC Press. This book was released on 2016-01-05 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogels are an emerging area of interest in medicine as well as pharmaceutics, and their physico-chemical characterization is fundamental to their practical applications. Compared with synthetic polymers, polysaccharides that are widely present in living organisms and come from renewable sources are extremely advantageous for hydrogel formation.
Download or read book Engineering Polymer Systems for Improved Drug Delivery written by Rebecca A. Bader and published by John Wiley & Sons. This book was released on 2014-01-17 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymers have played a critical role in the rational design and application of drug delivery systems that increase the efficacy and reduce the toxicity of new and conventional therapeutics. Beginning with an introduction to the fundamentals of drug delivery, Engineering Polymer Systems for Improved Drug Delivery explores traditional drug delivery techniques as well as emerging advanced drug delivery techniques. By reviewing many types of polymeric drug delivery systems, and including key points, worked examples and homework problems, this book will serve as a guide to for specialists and non-specialists as well as a graduate level text for drug delivery courses.
Download or read book Zeta Potential in Colloid Science written by Robert J. Hunter and published by Academic Press. This book was released on 2013-09-03 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zeta Potential in Colloid Science: Principles and Applications covers the concept of the zeta potential in colloid chemical theory. The book discusses the charge and potential distribution at interfaces; the calculation of the zeta potential; and the experimental techniques used in the measurement of electrokinetic parameters. The text also describes the electroviscous and viscoelectric effects; applications of the zeta potential to areas of colloid science; and the influence of simple inorganic ions or more complex adsorbates on zeta potential. Physical chemists and people involved in the study of colloid science will find the book useful.
Download or read book Dispersion Polymerization in Organic Media written by Keith E. J. Barrett and published by Wiley-Interscience. This book was released on 1974 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hydrogels in Medicine and Pharmacy written by Nikolaos A. Peppas and published by CRC Press. This book was released on 2019-08-15 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: First Published in 1986, this book offers a full, comprehensive guide to the application of hydrogels in medicine. Carefully compiled and filled with a vast repertoire of notes, diagrams, and references this book serves as a useful reference for students of medicine and other practitioners in their respective fields.
Download or read book Introduction to Soft Matter written by Ian W. Hamley and published by John Wiley & Sons. This book was released on 2013-03-18 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an introduction to this exciting and relativelynew subject with chapters covering natural and synthetic polymers,colloids, surfactants and liquid crystals highlighting the many andvaried applications of these materials. Written by an expert in thefield, this book will be an essential reference for people workingin both industry and academia and will aid in understanding of thisincreasingly popular topic. Contains a new chapter on biological soft matter Newly edited and updated chapters including updated coverageof recent aspects of polymer science. Contain problems at the end of each chapter to facilitateunderstanding
Download or read book Flowing Matter written by Federico Toschi and published by Springer Nature. This book was released on 2019-09-25 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book, published in the Soft and Biological Matter series, presents an introduction to selected research topics in the broad field of flowing matter, including the dynamics of fluids with a complex internal structure -from nematic fluids to soft glasses- as well as active matter and turbulent phenomena. Flowing matter is a subject at the crossroads between physics, mathematics, chemistry, engineering, biology and earth sciences, and relies on a multidisciplinary approach to describe the emergence of the macroscopic behaviours in a system from the coordinated dynamics of its microscopic constituents. Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. Phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strongly enough. This volume presents several research topics that address these phenomena encompassing the traditional micro-, meso-, and macro-scales descriptions, and contributes to our understanding of the fundamentals of flowing matter. This book is the legacy of the COST Action MP1305 “Flowing Matter”.
Download or read book Polymers as Biomaterials written by W. Shalaby and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nearly 4000 years ago, the Egyptians used linen, a natural polymeric material, for suturing wounds. About 600 B.C., the Indians used other forms of natural polymers such as cotton, horse hair, and leather in repairing wounds. Wound closure procedures using silk sutures, based mostly on polypeptides, are likely to have been practiced during the second century. Surgical application of natural polymers continued to represent the major use of polymers until the twentieth century. Not too long after the development of several major synthetic polymers, their use in biomedical applications has attracted the attention of many re searchers and clinicians. Over the past few years, interest in the biomedical applications of polymers has grown considerably. This has been the result of the inevitable collaborative efforts of in novative materials scientists, engineers and clinicians. The es tablishment of the Society for Biomaterials, in our opinion, cata lyzed the growing interest in the use of polymers for biomedical application. In a major effort to bring team players even closer, a five-day symposium on "Polymers as Biomaterials" was held in Seattle, Washing ton, in March, 1983 as part of the national meeting of the American Chemical Society. The symposium was designed to provide a forum for communicating technical and clinical data to colleagues with a broad spectrum of interest in the biomedical applications of polymers.
