Download or read book Kinetics and Mechanisms of Morphological Transitions in Block Copolymer Aggregates and Sodium Dodecyl Sulfate as a Morphogenic Agent microform written by Susan Elizabeth Burke and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2001 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Kinetics and Mechanisms of Morphological Transitions in Block Copolymer Aggregates and Sodium Dodecyl Sulfate as a Morphogenic Agent written by Susan Elizabeth Burke and published by . This book was released on 2001 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The kinetic and mechanistic details involved in the morphological transitions occurring in aggregates prepared from the copolymer polystyrene-b-poly(acrylic acid) (PS-b-PAA) in dioxane-water mixtures and the ability of sodium dodecyl sulfate to induce architectural changes in these aggregates are described in this dissertation. The kinetics of the sphere-to-rod, rod-to-sphere, and vesicle-to-rod transitions were determined by following the change in the solution turbidity as a function of time after the transitions were induced by a sudden jump in one of the solvent components of the system. The kinetics of each transition was explored as a function of the initial solvent composition, the magnitude of the solvent content jump, and the initial polymer concentration. In another study, the amphiphile, sodium dodecyl sulfate (SDS), was found to induce morphological transitions in the copolymer aggregates at lower water contents than those required in the absence of surfactant. The effect was studied as a function of SDS concentration, solvent composition, and copolymer concentration." --

Download or read book Morphological Control of Block Copolymer Aggregates in Aqueous Solutions written by Nichole Fairley and published by . This book was released on 2009 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: In aqueous media, amphiphilic block copolymers spontaneously self-assemble into nano-sized core-shell structures, termed block copolymer micelles. The ability for researchers to reliably reproduce morphologies in a controlled manner is of great interest because of the potential advantages and applications of copolymer aggregates with varying morphologies. This thesis describes the physico-chemical characteristics of polymer micelles, as well as the parameters which influence morphology in aqueous solution. The purpose of this research was to study the morphology of the amphiphilic block copolymer PEG5000-b-PCL4100 in aqueous solution. It was found that the amphiphilic block copolymer PEG5000-b-PCL 4100 could form long rod-like, short rod-like or spherical aggregates by controlling the copolymer concentration, or through the addition of a PEG-phospholipid to the copolymer. Overall, this research clearly demonstrates the ability to control block copolymer morphology which will inevitably play a pivotal role in the use of non-spherical micelles for pharmaceutical applications.

Download or read book Phase Behavior and Kinetics of Cylinder to Sphere Transition in Block Copolymers in Selective Solvents written by Minghai Li and published by . This book was released on 2008 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The main goal of this dissertation is to study the phase behavior and kinetics of cylinder to sphere phase transition in block copolymers in selective solvents using time- resolved small angle x-ray scattering (SAXS), rheology, Atomic Force Microscopy (AFM), modeling and simulation. Block copolymers consist of two or more chemically distinct polymer blocks connected by a covalent bond. The incompatibility of the constituent blocks leads to phase separation on length scales of 10-1000 nm instead of bulk phase separation. The addition of a selective solvent which preferentially solubilizes one of the components further enriches the phase behavior and provides easier control over the morphology of micellar domains. Although many studies have been made on the phase diagrams of block copolymer solutions the kinetics of phase transitions between two different crystalline symmetries are less understood. The experiments were conducted on a triblock copolymer of poly(styrene- b -ethylene- co -butylene- b -styrene) (SEBS), in mineral oil, a solvent selective to middle EB block. AFM measurements clearly showed the cylindrical micelles arranged hexagonally (HEX) at 110°C. Synchrotron based time-resolved SAXS measurements showed that the transition from HEX to spherical micelles arranged on body-centered cubic (BCC) lattice occurs via a nucleation and growth mechanism for shallow temperature jumps and via spinodal decomposition for deep temperature jumps. We developed a geometrical model of coupled anisotropic fluctuations to calculate the scattering and found very good agreement with the SAXS data. Brownian Molecular Dynamics simulations were carried out to provide microscopic insights on the HEX to cubic transition. HEX, face-centered cubic (FCC), lamellar, and hexagonally perforated lamellar ordered phases were obtained depending on the concentration, temperature and solvent selectivity. Kinetics of HEX to FCC was examined by quenching the temperature or rapidly changing the well-depth of the Lennard-Jones potential used in the simulation. The observations from snapshots, density profiles and calculated scattering intensity all agree well with the nucleation and growth mechanism. This work provides a detailed understanding of the mechanism and kinetics of phase transition of cylinders to spheres in block copolymer solution system. The results have relevance to block copolymer processing and other applications.

Download or read book Morphological Transitions in Block Copolymers written by Damian Andrew Hajduk and published by . This book was released on 1994 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystallization induced Aggregation of Block Copolymer Micelles Influence of Crystallization Kinetics on Morphology written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Morphological Transition in SBS Block Copolymers written by Loretta Young and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermodynamic and Kinetic Aspects of Morphological Transitions of Diblock Copolymer Self assemblies in Solution written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Phase Behavior of Block Copolymers in Selective Solvents written by Yongsheng Liu and published by . This book was released on 2008 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The goal of this research is to study the phase behavior and kinetics of order-order (OOT) and order-disorder (ODT) phase transitions in block copolymers in selective solvents. We focus on examining temperature and pressure dependence of the phase diagram and the kinetics of phase transitions using small angle x-ray scattering (SAXS). The kinetics of ODT and OOT was studied for two block copolymer solutions by time-resolved SAXS using temperature ramp and fast quench methods: (i) Poly(styrene- b -isoprene) (PS-PI) diblock copolymer in tetradecane, selective solvent for PI, which displayed face-centered-cubic (FCC) structure at low temperature, body-centered-cubic (BCC) at intermediate temperature, and was disordered at high temperature. Following a quench from 110 C to 50 C, a long-lived meta-stable BCC phase was detected prior to the formation of FCC. The data agrees very well with Cahn's model for nucleation and growth. (ii) Poly(styrene- b -ethylene- co -butylene- b -styrene) triblock copolymer in dibutyl phthaphate, selective solvent for PS, which displayed hexagonally packed cylinders (HEX) at low temperature and lamellar (LAM) phase at high temperatures. This is unusual because in most block copolymer melts LAM occurs at lower temperature than HEX. A geometric model was developed to understand the mechanism of the transition from LAM to HEX. The calculated scattering intensity agrees very well with the experimental data. A pressure network system for SAXS capable of operating in the range of 1-4000 bars with pressure jump capability was built to study the pressure dependence of phase behavior. The system was used to investigate PS-PI diblock copolymer in diethyl phthaphate. The BCC to disorder transition temperature increased with pressure at 20 C/kbar, and the lattice constant increased with pressure. Brownian Molecular Dynamics simulations were carried out to study the phase behavior of multiblock copolymers in a selective solvent. Disordered, BCC, HEX, and LAM phases were obtained depending on the concentration and number of blocks. This research provides detailed information of the kinetics of structural changes in block copolymers in selective solvents. The results provide a good understanding of the mechanism of order-disorder and order-order transitions, and are directly related to industrial applications of block copolymers.

Download or read book Morphologies and Morphological Transitions in Binary Blends of Diblock Copolymer and Homopolymer written by Karen Irene Winey and published by . This book was released on 1991 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Manipulating Phase Behavior in Block Copolymers Using Polydispersity written by and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of polydispersity, or broad molecular weight distributions, on the phase behavior of block copolymer melts and thin films are systematically explored. Linear AB diblock, ABA triblock, and BAB triblock copolymers are synthesized with continuous polydispersity in the B block (Mw/Mn 8́ơ 1.70́32.0) and relatively monodisperse A blocks (Mw/Mn 8́ơ 1.10́31.3) to understand how the self0́3assembly of polydisperse block copolymers can be altered with chain architecture and block connectivity. Broad dispersity in the M block of poly(styrene0́3b0́3methyl methacrylate) (SM) diblock copolymer melts induces domain dilation and morphological transitions to higher M block volume compositions with respect to predictions for monodisperse SM diblock copolymers. A comparison between poly(styrene0́3b0́31,40́3butadiene0́3b0́3styrene) triblock copolymers (SBS) with mid0́3block (B) polydispersity and poly(methyl methacrylate0́3b0́3styrene0́3b0́3methyl methacrylate) triblock copolymers (MSM) with outer0́3block (M) polydispersity reveals that the location of the polydisperse block and how it is connected to the other blocks is critical. Center block polydispersity in SBS, where one block is constrained at two block junctions, leads to a lamellar phase window shift to higher volume fractions of B, increases in domain periodicity, and the stabilization of a new, disordered bicontinuous morphology. The domain periodicity in the MSM triblocks with outer M block polydispersity is at least twice that predicted for monodisperse MSM triblock copolymers. However, in contrast to the SBS triblocks, the polydisperse MSM triblocks exhibit a lamellar phase window shift to lower M block compositions. The behavior of the SBS and MSM triblock copolymers is clarified in the context of the chain architectures present in the melts resulting from the block polydispersity. Preliminary studies of the thin film behavior of the SM diblock and MSM triblock copolymers revealed that despite the polydispersity of the M block, perpendicular microdomain orientation can be achieved. The MSM triblock copolymer thin films exhibit film thickness0́3dependent morphological behavior arising from a confluence of M outer0́3block polydispersity and the presence of a random brush0́3modified substrate. In summation, this dissertation demonstrates that polydispersity can be used to manipulate the phase behavior of block copolymer melts and thin films and may facilitate access to new materials with potentially useful properties.

Download or read book Controlling Morphology of Multi component Block Copolymer Based Materials written by Rafal Adam Mickiewicz and published by . This book was released on 2009 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability of block copolymers to self-assemble into ordered microstructures has attracted much interest both from a pure scientific perspective and for their potential in numerous industrial applications. The microphase separation of block copolymers has been successfully exploited in a wide range of applications, such as templating and lithography, enhancement of mechanical properties, and nano reactor schemes. This thesis focuses on the characterization of the morphology in composite systems where one or more of the components is a block copolymer. In the first part of this thesis, binary blends of very high molecular weight diblock copolymers with a low molecular weight triblock copolymer are investigated. The high molecular weight diblock copolymers are very strongly segregating, with interaction parameter values, XN, in the range 470 - 1410. The phase diagram revealed a large miscibility gap for the blends, with macrophase separation into two distinct types of microphase separated domains and implied virtually no solubility of the much higher molecular weight diblocks in the triblock. For certain blend compositions, morphological transitions from the lamellar to cylindrical and bicontinuous structures were also observed, even though the overall composition in the blend would be expected to favor the lamellar microstructure. This was found to result from the compositional asymmetry of the triblock copolymer influencing the curvature of the inter-material dividing surface (IMDS). Finally, a strong segregation theory model was used to interpret the observed results. In the second part of this thesis the microstructure formation in nanocomposites based on a liquid crystalline side chain block copolymer (LCBCP) and gold nanoparticles was investigated. The location of the nanoparticles was found to not only depend on the surface chemistry of the gold nanoparticles, but also on the self-organization within the liquid crystalline domain of the LCBCP. The nanoparticles were excluded from the liquid crystalline domains due to the high free energy penalty of disrupting the smectic layering. The final location of the nanoparticles within the composite was determined by the nature of the stabilizing surface coating. The work presented in this thesis revealed a number of interesting tools which are useful for obtaining a wide range of morphologies in multi-component block copolymer systems.

Download or read book Biological Matrices and Tissue Reconstruction written by G. Björn Stark and published by . This book was released on 1998 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: C.A. VACANTI The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in human health care. Advances in the medical sciences have enabled physicians to restore lost functions in their patients through or gan transplantation, reconstructive surgery with autogenous tissue transfer, or the implantation of alloplastic materials. Although only recently termed "Tissue Engineering" [1], the use of biological andlor synthetic materials in conjunction with cells to create biologic substitutes to serve as functional tis sue replacements has been explored by modern scientists for several decades. The concept of generating functional tissue from an organ biopsy was de scribed very early in the literature: "The Lord God cast a deep sleep on the man, and while he was asleep, he took out one of his ribs and closed up its place with flesh. The Lord God then built up into a woman the rib that he had taken from the man" [2]. Review of history further reveals that, according to legend, the first homotransplantation of an entire limb was performed by Saints Damian and Cosmas, as depicted by the artist Fra Angelico.

Download or read book Inclusions in Prokaryotes written by Jessup M. Shively and published by Springer Science & Business Media. This book was released on 2006-05-04 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: The new series "Microbiology Monographs" begins with two volumes on intracellular components in prokaryotes. In this first volume, "Inclusions in Prokaryotes", the components, labeled inclusions, are defined as discrete bodies resulting from synthesis of a metabolic product. Research on the biosynthesis and reutilization of the accumulated materials is still in progress, and interest in the inclusions is growing. This comprehensive volume provides historical background and comprehensive reviews of eight well-known prokaryotic inclusions.

Download or read book Nanostructures for Antimicrobial and Antibiofilm Applications written by Ram Prasad and published by Springer Nature. This book was released on 2020-05-12 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the pursuit of technological advancement in the field of biotechnology and pharmaceutical industries to counteract health issues, bacterial infections remain a major cause of morbidity and mortality. The ability of bacterial pathogens to form biofilms further agglomerates the situation by showing resistance to conventional antibiotics. To overcome this serious issue, bioactive metabolites and other natural products were exploited to combat bacterial infections and biofilm-related health consequences. Natural products exhibited promising results in vitro, however; their efficacy in in vivo conditions remain obscured due to their low-solubility, bioavailability, and biocompatibility issues. In this scenario, nanotechnological interventions provide a multifaceted platform for targeted delivery of bioactive compounds by slow and sustained release of drug-like compounds. The unique physico-chemical properties, biocompatibility and eco-friendly nature of bioinspired nanostructures has revolutionized the field of biology to eradicate microbial infections and biofilm-related complications. The green-nanotechnology based metal and metal oxide nanoparticles and polymeric nanoparticles have been regularly employed for antimicrobial and antibiofilm applications without causing damage to host tissues. The implications of these nanoparticles toward achieving sustainability in agriculture by providing systemic resistance against a variety of phytopathogens therefore plays crucial role in growth and crop productivity. Also the advent of smart and hybrid nanomaterials such as metal-based polymer nanocomposites, lipid-based nanomaterials and liposomes have the inherent potential to eradicate bacterial biofilm-related infections in an efficient manner. The recent development of carbon-based nanomaterials such as carbon nanotubes (CNTs) and silica based nanomaterials such as mesoporous silica nanoparticles (MSNs) also exploit a target of dreadful healthcare conditions such as cancer, immunomodulatory diseases, and microbial infections, as well as biofilm-related issues owing to their stability profile, biocompatibility, and unique physio-chemical properties. Recently novel physical approaches such as photothermal therapy (PTT) and antimicrobial photodynamic therapy (aPDT) also revolutionized conventional strategies and are engaged in eradicating microbial biofilm-related infections and related health consequences. These promising advancements in the development of novel strategies to treat microbial infections and biofilm-related multidrug resistance (MDR) phenomenon may provide new avenues and aid to conventional antimicrobial therapeutics.

Download or read book Marine and Industrial Biofouling written by Hans-Curt Flemming and published by Springer Science & Business Media. This book was released on 2008-12-11 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biofouling is a costly problem, and it is encountered in a wide spectrum of technical systems, ranging from the shipping industry, power industry, water purification, automobile industry, paint and pharmaceuticals, to the microelectronics and food industries. Micro- and macroorganisms attach to surfaces and accumulate there, forming biofilms that cause interferences – a fundamentally natural process. Usually, a medical paradigm is applied: kill biofilms and the problem is solved. This leads to excessive biocide use. However, the success of this strategy is very limited; furthermore it leads to equipment damage and environmental pollution. Simply trying to kill the fouling organisms is clearly not seen as a successful strategy while cleaning is put forward as much more important. In this book, strategies to prevent adhesion, to mitigate the extent and effects of biofouling, and to detect and remove fouling layers are presented. Holistic approaches to the fouling process are elaborated, taking into account options such as nutrient limitation, repellent and easy-to-clean surfaces for fouling layer limitation, and replacing biocides with more environmentally friendly methods – in other words: learning how to live with fouling biofilms without suffering the damage they can do.

Download or read book Cellular and Molecular Biology of Intermediate Filaments written by R.D. Goldman and published by Springer. This book was released on 2013-05-05 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research activity on intermediate filaments (IF) has increased dramatically over the past decade. For the most part, this surge of interest is due to their identification as ubiquitous constituents of the cytoskeleton and karyoskeleton (nuclear matrix) of eukaryotic cells and the fact that we know very little regarding their functions. In sharp contrast to the other major cytoskeletal systems, microfilaments and microtubules, IF exhibit a high degree of heterogeneity with regard to their protein subunit composition. Indeed, one can only marvel at the number of different IF polypeptides, their associated proteins (IFAP) and, consequently, the number of genes involved in encoding the multiple constituents of the various IF networks found in different cell types. The chapters in this book demonstrate how various experimental approaches involv ing cellular, molecular, biochemical, and immunological methods have been utilized to generate information regarding the structure and function of IF. To this end, we have gathered together chapters from experts in the major fields of IF research. In each chapter, the authors have combined reviews of the available scientific literature with their own ideas on current and future directions for IF research. The chapters have been divided into five major sections which are concerned with the subcellular organization of IF, the molecular structure of IF, the differential expression of IF genes, descriptions of associ ated proteins involved in the intracellular organization of IF, and finally an analysis of the changes seen in IF in pathological conditions.