Download or read book Diblock Copolymer Phase Behavior Near the Order disorder Transition written by Mark Frederic Schulz and published by . This book was released on 1995 with total page 476 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 Order Disorder Transitions in Cross Linked Block Copolymer Solids written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With a view toward creating solid block copolymers wherein the order-disorder transition can be accessed many times they investigated the nature of order-disorder transitions in cross-linked diblock copolymer melts using synergistic theory and experiment. A mean-field theory based on a coarse grained free-energy and the Random Phase Approximation (RPA) is developed for the system of interest. The quenched distribution of cross-links is averaged using the replica method. The phase behavior of a particular A-B block copolymer melt with a randomly cross-linked B-Block is determined as a function of the Florry-Huggins interaction parameter ([chi]) and the average number of cross-links per chain N{sub c}. They find for a cross-link density greater than N*{sub c} the B monomers are localized within a region of size [zeta] H"(N{sub c} - N*{sub c})−12. The cross-links strongly oppose ordering in the system as [zeta] becomes comparable to the radius of gyration of the block copolymer chain. As such the order-disorder transition temperature T{sub ODT} decreases precipitously when N{sub c}> N*{sub c}. When N{sub c}
Download or read book Phase Behavior Structure and Properties of Model Block Polymers written by and published by . This book was released on 1993 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project brought together three distinct experimental methods in an integrated investigation of the phase behavior, structure and properties of block copolymers in the vicinity of the order-disorder transition. Anionic polymerization of polydiene diblock copolymers followed by catalytic hydrogenation was used to produce three classes of model saturated hydrocarbon materials. Dynamic mechanical spectroscopy and large amplitude dynamic shearing were employed to probe and manipulate, respectively, the melt state microstructure. Small angle neutron scattering (SANS) experiments provided detailed information regarding the structure of the materials. A significant achievement during this work was the development of a dynamic shearing device that could be operated in situ with a SANS instrument. Together with the spectrum of materials produced, this combined scattering-rheology technique has led to a qualitative improvement in our understanding of block copolymer phase behavior, and uncovered a rich polymorphism that is accompanied by dramatic variations in physical properties. Two new parameters have been shown to play a crucial role in determining block copolymer phase behavior. The degree of polymerization, controls the extent of composition fluctuations which strongly affects the types of phases encountered near the order-disorder transition. Conformational asymmetry, which is controlled by the block volume and radius of gyration, leads to different phases on either side of the phase diagram. These effects have not been accounted for theoretically.
Download or read book Polyolefin Diblock Copolymers Near the Order disorder Transition written by Jeffrey Harris Rosedale and published by . This book was released on 1993 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Simulating the Fluctuation Induced Suppression of the Order Disorder Transition in an Asymmetric Diblock Copolymer Melt written by Jeffrey Roberts and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mean-field theory predicts the phase behaviour of block copolymers with a great deal of success, however it systematically overestimates the order-disorder temperature (ODT) due to its inaccurate treatment of fluctuations in the disordered phase. We use Monte Carlo simulation to simulate a fluctuating melt of asymmetric diblock copolymers, and systematically investigate the suppression of the ODT as we decrease the invariant degree of polymerization, N̄, from 106 to 105. Using thermodynamic integration, we compare the ordered BCC sphere phase free energy to that of the disordered phase to locate the ODT. In the low-temperature regime of the disordered phase, we observe and characterize a disordered liquid of micelles that is stabilized by the inclusion of fluctuations in our simulation. We find that decreasing N̄ causes a suppression of the ODT that is in good agreement with a theory where fluctuations are incorporated on a single-mode Hartree level.
Download or read book Phase Behavior of Block Copolymers in Compressed CO2 and as Single Domain layer Nanolithographic Etch Resists for Sub 10 Nm Pattern Transfer written by Curran Matthew Chandler and published by . This book was released on 2011 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diblock copolymers have many interesting properties, which first and foremost include their ability to self-assemble into various ordered, regularly spaced domains with nanometer-scale feature sizes. The work in this dissertation can be logically divided into two parts - the first and the majority of this work describes the phase behavior of certain block copolymer systems, and the second discusses real applications possible with block copolymer templates. Many compressible fluids have solvent-like properties dependent on fluid pressure and can be used as processing aids similar to liquid solvents. Here, compressed CO2 was shown to swell several thin homopolymer films, including polystyrene and polyisoprene, as measured by high pressure ellipsometry at elevated temperatures and pressures. The ellipsometric technique was modified to produce accurate data at these conditions through a custom pressure vessel design. The order-disorder transition (ODT) temperatures of several poly(styrene-b-isoprene) diblock copolymers were also investigated by static birefringence when dilated with compressed CO2. Sorption of CO2 in each copolymer resulted in significant depressions of the ODT temperature as a function of fluid pressure, and the data above was used to estimate the quantitative amount of solvent in each of the diblock copolymers. These depressions were not shown to follow dilution approximation, and showed interesting, exaggerated scaling of the ODT at near-bulk polymer concentrations. The phase behavior of block copolymer surfactants was studied when blended with polymer or small molecule additives capable of selective hydrogen bonds. This work used small angle X-ray scattering (SAXS) to identify several low molecular weight systems with strong phase separation and ordered domains as small as 2-3 nanometers upon blending. One blend of a commercially-available surfactant with a small molecule additive was further developed and showed promise as a thin-film pattern transfer template. In this scenario, block copolymer thin films on domain thick with self-assembled feature sizes of only 6-7 nm were used as plasma etch resists. Here the block copolymer's pattern was successfully transferred into the underlying SiO2 substrate using CF4-based reactive ion etching. The result was a parallel, cylindrical nanostructure etched into SiO2.
Download or read book Phase Behavior of Diblock Copolymer Mixtures written by Jin Zhao and published by . This book was released on 1995 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phase Behavior and Kinetics of Disorder order and Order order Transitions in Multi block Copolymers in Selective Solvents written by Huifen Nie and published by . This book was released on 2005 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phase Transitions in Polymers The Role of Metastable States written by Stephen Z.D. Cheng and published by Elsevier. This book was released on 2008-09-10 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: A classical metastable state possesses a local free energy minimum at infinite sizes, but not a global one. This concept is phase size independent. We have studied a number of experimental results and proposed a new concept that there exists a wide range of metastable states in polymers on different length scales where their metastability is critically determined by the phase size and dimensionality. Metastable states are also observed in phase transformations that are kinetically impeded on the pathway to thermodynamic equilibrium. This was illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification and gel formation, as well as combinations of these transformation processes. The phase behaviours in polymers are thus dominated by interlinks of metastable states on different length scales. This concept successfully explains many experimental observations and provides a new way to connect different aspects of polymer physics. * Written by a leading scholar and industry expert* Presents new and cutting edge material encouraging innovation and future research* Connects hot topics and leading research in one concise volume
Download or read book Current Topics in Elastomers Research written by Anil K. Bhowmick and published by CRC Press. This book was released on 2008-05-07 with total page 1105 pages. Available in PDF, EPUB and Kindle. Book excerpt: From weather-proof tires and artificial hearts to the o-rings and valve seals that enable successful space exploration, rubber is an indispensable component of modern civilization. Stiff competition and stringent application requirements foster continuous challenges requiring manufacturers to fund ever-expanding research projects. However, this vas
Download or read book Holographic Sensors written by Ali Kemal Yetisen and published by Springer. This book was released on 2014-12-03 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a theoretical and experimental approach for the rapid fabrication, optimization and testing of holographic sensors for the quantification of pH, organic solvents, metal cations, and glucose in solutions. Developing non-invasive and reusable diagnostics sensors that can be easily manufactured will support the monitoring of high-risk individuals in any clinical or point-of-care setting. Sensor fabrication approaches outlined include silver-halide chemistry, laser ablation and photopolymerization. The sensors employ off-axis Bragg diffraction gratings of ordered silver nanoparticles and localized refractive index changes in poly (2-hydroxyethyl methacrylate) and polyacrylamide films. The sensors exhibited reversible Bragg peak shifts, and diffracted the spectrum of narrow-band light over the wavelength range λpeak ≈ 495-1100 nm. Clinical trials of glucose sensors in the urine samples of diabetic patients demonstrated that they offer superior performance compared to commercial high-throughput urinalysis devices. Lastly, a generic smartphone application to quantify colorimetric tests was developed and tested for both Android and iOS operating systems. The sensing platform and smartphone application may have implications for the development of low-cost, reusable and equipment-free point-of-care diagnostic devices.
Download or read book Structure and Interactions in Concentrated Diblock Copolymer Solutions written by Glen A. McConnell and published by . This book was released on 1996 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymer Materials written by Kwang-Sup Lee and published by Springer. This book was released on 2010-08-12 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: -On the Mechanisms Leading to Exfoliated Nanocomposites Prepared by Mixing By C. D. Han -Phase Behavior and Phase Transitions in AB- and ABA-type Microphase-Separated Block Copolymers By J. K. Kim, C. D. Han -New Class Materials of Organic–Inorganic Hybridized Nanocrystals/Nanoparticles, and Their Assembled Microand Nano-Structure Toward Photonics By H. Oikawa, T. Onodera, A. Masuhara, H. Kasai, H. Nakanishi -Poly(substituted Methylene) Synthesis: Construction of C–C Main Chain from One Carbon Unit By E. Ihara
Download or read book Block Copolymers written by Kenneth J. Hanley and published by . This book was released on 2001 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Polymer Thermodynamics written by Sabine Enders and published by Springer. This book was released on 2011-01-18 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Making Flory-Huggins Practical: Thermodynamics of Polymer-Containing Mixtures, by B. A. Wolf * Aqueous Solutions of Polyelectrolytes: Vapor-Liquid Equilibrium and Some Related Properties, by G. Maurer, S. Lammertz, and L. Ninni Schäfer * Gas-Polymer Interactions: Key Thermodynamic Data and Thermophysical Properties, by J.-P. E. Grolier, and S. A.E. Boyer * Interfacial Tension in Binary Polymer Blends and the Effects of Copolymers as Emulsifying Agents, by S. H. Anastasiadis * Theory of Random Copolymer Fractionation in Columns, by Sabine Enders * Computer Simulations and Coarse-Grained Molecular Models Predicting the Equation of State of Polymer Solutions, by K. Binder, B. Mognetti, W. Paul, P. Virnau, and L. Yelash * Modeling of Polymer Phase Equilibria Using Equations of State, by G. Sadowski
