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Book Crystallization Crystal Orientation and Morphology of Poly ethylene Oxide Under One Dimensional Defect free Confinement on the Nanoscale

Download or read book Crystallization Crystal Orientation and Morphology of Poly ethylene Oxide Under One Dimensional Defect free Confinement on the Nanoscale written by Ming-Siao Hsiao and published by . This book was released on 2009 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: "One dimensionally (1D) confined crystallization based on semicrystalline diblock copolymers has been widely investigated for twenty years. Highly orientated lamellar samples, after large amplitude oscillation shear, provide the typical 1D confined environment to investigate crystallization behavior, such as crystal orientation and crystallization kinetics. However, inevitable defect generation, such as edge and screw dislocations during mechanical shear lead to "cross-talking" between grain boundaries and significantly affect the ideal 1D confinement crystallization kinetics by releasing the confinement. Meanwhile, the mechanism of the origin of specific crystal orientations (parallel or perpendicular) within the 1D confinement is still under debate. In this research, PS-b-PEO single crystals composed of one PEO nano-layer sandwiched by two PS glassy layers on the nanoscale were chosen as a template to investigate polymer crystallization in a 1D defect-free nanoscale confinement. Since the TgPS is higher than the TmPEO in such a "sandwich" lamellar structure, the PEO single crystal can be melted while keeping the PS layer in the vitrified state. The PEO blocks can be recrystallized between the two confining, glassy PS nano-layers at different re-crystallization temperatures, Trx, and monitored for different recrystallization behavior using electron diffraction (ED). Results indicate that the PEO block does not recrystallize until Trx = -5°C, the limit of homogeneous nucleation. This observation confirms PEO recrystallization takes place in a defect-free confinement. Next, a puzzling ED pattern taken from PEO microcrystals grown at Trx>-5°C via self-seeding was analyzed to be the result of the specific interaction between tethered PEO blocks having monoclinic symmetry and the glassy PS substrate. Two different inclined PEO microcrystals having an orthogonal relationship truly coexisting in the lamellar confinement during self-seeding were found. Furthermore, PS-b-PEO single crystal mats provide a template for investigating how confined dimension (dPEO) and reduced tethering density (PEO) affect the Trx dependent crystal orientation. The results show that a dramatic change of PEO crystal orientation from parallel to perpendicular with respect to the PS lamellar plane within 1°C when Trx is close to the limit of PEO homogeneous nucleation. The crystal orientation may have resulted from a competition of the PEO segmental orientation near the PS and PEO interfaces, which is determined by reduced tethering density with anisotropies of the overall chain conformation; and density fluctuations of the PEO melt due to the confinement of the PS layers. This study hopes to provide a universal principle to answer the debate over 1D confined crystallization. Finally, the interplay of three factors (lamellar confined volume (V), confined dimension (dPEO) and reduced tethering density (PEO) determine the final onset temperature of the sharp crystal orientation change, and the distribution of these Tonset values are over 31°C."--Abstract.

Book Dynamics of Soft Matter

Download or read book Dynamics of Soft Matter written by VICTORIA GARCIA SAKAI and published by Springer Science & Business Media. This book was released on 2011-12-18 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamics of Soft Matter: Neutron Applications provides an overview of neutron scattering techniques that measure temporal and spatial correlations simultaneously, at the microscopic and/or mesoscopic scale. These techniques offer answers to new questions arising at the interface of physics, chemistry, and biology. Knowledge of the dynamics at these levels is crucial to understanding the soft matter field, which includes colloids, polymers, membranes, biological macromolecules, foams, emulsions towards biological & biomimetic systems, and phenomena involving wetting, friction, adhesion, or microfluidics. Emphasizing the complementarities of scattering techniques with other spectroscopic ones, this volume also highlights the potential gain in combining techniques such as rheology, NMR, light scattering, dielectric spectroscopy, as well as synchrotron radiation experiments. Key areas covered include polymer science, biological materials, complex fluids and surface science.

Book Crystallization Kinetics of Poly ethylene Oxide

Download or read book Crystallization Kinetics of Poly ethylene Oxide written by Frances H. Segouin and published by . This book was released on 1994 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The three main goals of this project are to determine the molecular weight dependence of polyethylene oxide) on the 1) morphology of crystalline material, as seen with the polarizing light microscope, 2) nucleation of the crystalline phase, as demonstrated with an annealing study, and 3) parameters of a mathematical model for crystallization kinetics. Bulk crystallization kinetics of polyethylene oxide) from the melt have been studied for a large molecular weight range, 1500 g/mol to 7,000,000 g/mol. The effects of molecular weight and cooling rate on the width and degree of supercooling of DSC crystallization exotherms have been studied to determine the type of nucleation involved and to determine the relationship between the DSC signals and the morphology of a crystalline sample. As the molecular weight increases, at a cooling rate of twenty degrees per minute, the width-at-half- height of the exothermic DSC peak decreases from seven degrees to approximately three degrees for the low molecular weight samples and increases from three to seven degrees for the high molecular weight samples. The degree of supercooling at which the peaks reach a maximum generally increases from twelve degrees Celsius to above twenty degrees Celsius. The slower the cooling rate the narrower the width at half height of the crystallization peak and the lower the degree of supercooling at the maximum point of the crystallization exotherms. For all of the molecular weight samples, the crystallization peak temperatures increase in the range of one to ten degrees of supercooling from a one-degree-per-minute cooling rate to a twenty degrees-per-minute cooling rate. The average width-at-half-height increases from three to six- degrees Celsius from the one degree-per-minute cooling rate experiment to the twenty degreesper- minute cooling rate experiment. The morphology of the samples varied from a coarse non-interconnected lamellae formation below the critical molecular weight to an interconnected lamellae formation, also known as a spherulite, above the critical molecular weight. The critical molecular weight for polyethylene oxide) is 3400 g/mol. Based on the expression for the linear crystal growth rate, reported by Cheng et al.1, a mathematical model was created to model the DSC crystallization curves. This model, which incorporates heat transfer effects, can model the width and shape of the DSC curves, but the degree of supercooling that the model predicts is generally smaller than the experimental degree of supercooling. While modeling the DSC crystallization curves, it was found that the activation energy for reptation motion, U*, has less of an effect on the model crystallization curves than does the surface energy term, Kg, of the Cheng growth rate expression."--Abstract.

Book Morphology and Phase Behavior of Poly ethylene Oxide Blends

Download or read book Morphology and Phase Behavior of Poly ethylene Oxide Blends written by Sudhakar Balijepalli and published by . This book was released on 1996 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Polymer Morphology

Download or read book Polymer Morphology written by Qipeng Guo and published by John Wiley & Sons. This book was released on 2016-05-16 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: With a focus on structure-property relationships, this book describes how polymer morphology affects properties and how scientists can modify them. The book covers structure development, theory, simulation, and processing; and discusses a broad range of techniques and methods. • Provides an up-to-date, comprehensive introduction to the principles and practices of polymer morphology • Illustrates major structure types, such as semicrystalline morphology, surface-induced polymer crystallization, phase separation, self-assembly, deformation, and surface topography • Covers a variety of polymers, such as homopolymers, block copolymers, polymer thin films, polymer blends, and polymer nanocomposites • Discusses a broad range of advanced and novel techniques and methods, like x-ray diffraction, thermal analysis, and electron microscopy and their applications in the morphology of polymer materials

Book End Group Dependence of Melt Crystallization Behavior of Low molecular weight Poly ethylene Oxide Fractions and Morphology Study

Download or read book End Group Dependence of Melt Crystallization Behavior of Low molecular weight Poly ethylene Oxide Fractions and Morphology Study written by Scott Shiaoshin Wu and published by . This book was released on 1994 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Solution Crystallization of Poly ethylene Oxide Bottle Brushes

Download or read book Solution Crystallization of Poly ethylene Oxide Bottle Brushes written by Xiting Liu and published by . This book was released on 2017 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer bottle brush (BB) as a newly developed polymer architecture has attracted a lot of attention in the materials science field. Polymer bottle brushes usually have high molecular weight and a worm-like shape. Polymer bottle brushes have side chains that are closely covalently bonded to a linear polymer backbone. Because of the close packing of side chains, the backbone is extended. Polymer bottle brushes are well-defined polymers by controlling the side chains, backbone and grafting density. The study of crystallization behavior of polymer bottle brush is essential for us to gain a better knowledge of polymer bottle brush. In this thesis study, we investigated the crystallization behavior of poly(ethylene oxide) BB (PEO-BB) in dilute solution. 5K PEO side chain was used as the side chain of the polymer bottle brush(BB). The degree of polymerization of backbone is 800 and the grafting density is controlled to be 76% and 48.6%. Uniformly spherical single crystals structure have been observed in PEO-BB. Furthermore, the size of the spherical crystals increases with the increasing crystallization temperature. Single layer structure transfers into a muti-lay structure when the concentration of the solution increases. Programmable growth was also conducted in this research, using different size of 300Klinear PEO single crystals as the seeds in the solution. A plethora of single crystal morphologies have been observed, and the detailed formation mechanism will be discussed.

Book Relationships Between Morphological Characteristics Kinetics of Crystallization and Crystallization Temperature for the Dilute Solution Crystallization of Poly ethylene Oxide

Download or read book Relationships Between Morphological Characteristics Kinetics of Crystallization and Crystallization Temperature for the Dilute Solution Crystallization of Poly ethylene Oxide written by Elaine Rose Williams and published by . This book was released on 1971 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Flow Induced Crystallization of Poly Ethylene Oxide

Download or read book Flow Induced Crystallization of Poly Ethylene Oxide written by Audrey Mack and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this research is to study the flow-induced crystallization of poly- (ethylene oxide) of different molecular weights using rotational rheometry. Experiments were carried out to determine the behavior of the material in the melt state, specifically as functions of frequency and shear rate. The quiescent crystallization behavior of PEO was studied, and the impact of flow on this crystallization behavior was explored in detail. The goal of this work was to establish the criteria for the onset of flow-induced crystallization, to determine if a point exists when the increased rate of crystallization will begin to level off or decrease (saturation point) in PEOs with different molecular weights and molecular weight distributions, and to determine the governing parameter of FIC in PEO. Parameters that were considered include shearing time, shearing rate, shearing temperature and specific work applied. The strengths of FIC effects were compared to the fraction of stretchable chains in the molecular weight distributions.

Book Nanoporous Alumina

Download or read book Nanoporous Alumina written by Dusan Losic and published by Springer. This book was released on 2015-07-17 with total page 371 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives detailed information about the fabrication, properties and applications of nanoporous alumina. Nanoporous anodic alumina prepared by low-cost, simple and scalable electrochemical anodization process due to its unique structure and properties have attracted several thousand publications across many disciplines including nanotechnology, materials science, engineering, optics, electronics and medicine. The book incorporates several themes starting from the understanding fundamental principles of the formation nanopores and theoretical models of the pore growth. The book then focuses on describing soft and hard modification techniques for surface and structural modification of pore structures to tailor specific sensing, transport and optical properties of nano porous alumina required for diverse applications. These broad applications including optical biosensing, electrochemical DNA biosensing, molecular separation, optofluidics and drug delivery are reviewed in separated book chapters. The book appeals to researchers, industry professionals and high-level students.

Book Development of Crystalline Morphology in Polyethylene and PEEK

Download or read book Development of Crystalline Morphology in Polyethylene and PEEK written by I. A. M. Al Raheil and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: