Download or read book Order Disorder Transitions in Block Copolymers Melts Dilated with Compressible Fluids written by Bryan D. Vogt and published by . This book was released on 1999 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 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 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 Characterization of Order order and Order disorder Transitions in a Block Copolymer Blend written by Maulik A. Modi and published by . This book was released on 1998 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Design of Ordering Transitions in Block Copolymers written by Anne-Valérie Geneviève Ruzette and published by . This book was released on 2000 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics Studies of a Block Copolymer Melt written by Amish Jagdish Patel and published by . This book was released on 2007 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Block Number on the Order disorder Transition Viscoelastic Properties and Shear Alignment Behavior of Linear AB n Multiblock Copolymers written by Lifeng Wu and published by . This book was released on 2004 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Soft tetramer Model for Diblock Copolymer Melts written by Claudine Groß and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2011-03 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability of block copolymers to spontaneously self-assemble into a variety of ordered nano-structures not only makes them a scientifically interesting system for the investigation of order-disorder phase transitions, but also offers a wide range of nano-technological applications. The architecture of a diblock is the most simple among the block copolymer systems, hence it is often used as a model system in both experiment and theory. We introduce a new soft-tetramer model for efficient computer simulations of diblock copolymer melts. The instantaneous non-spherical shape of polymer chains in molten state is incorporated by modeling each of the two blocks as two soft spheres. The interactions between the spheres are modeled in a way that the diblock melt tends to microphase separate with decreasing temperature. Using Monte Carlo simulations, we determine the equilibrium structures at variable values of the two relevant control parameters, the diblock composition and the incompatibility of unlike components. The simplicity of the model allows us to scan the control parameter space in a completeness that has not been reached in previous molecular simulations. The resulting phase diagram shows clear similarities with the phase diagram found in experiments. Moreover, we show that structural details of block copolymer chains can be reproduced by our simple model. We develop a novel method for the identification of the observed diblock copolymer mesophases that formalizes the usual approach of direct visual observation, using the characteristic geometry of the structures. A cluster analysis algorithm is used to determine clusters of each component of the diblock, and the number and shape of the clusters can be used to determine the mesophase. We also employ methods from integral geometry for the identification of mesophases and compare their usefulness to the cluster analysis approach. To probe the properties of our model in confinement, we perform molecular dynamics simulat.
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 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 Order to disorder Transition in Semidilute Block Copolymer Solutions written by Serena Sacks and published by . This book was released on 1994 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Shear on Order disorder and Order order Transitions in Block Copolymers written by Chien-Yueh Huang and published by . This book was released on 1996 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermodynamics and Surfactancy of Block Copolymers in Multicomponent Polyolefin Blends written by Joon-Hyung Lee and published by . This book was released on 2002 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Orientational Transitions in Block copolymer Melts Under Shear Flow written by Alexander Nicolaevitch Morozov and published by . This book was released on 2001 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
