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Photopolymerization Induced Phase Separation And Morphology Development In Liquid Crystal Polymer Blends
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Book Synopsis Photopolymerization-induced Phase Separation and Morphology Development in Liquid Crystal/polymer Blends by : Domasius Nwabunma
Download or read book Photopolymerization-induced Phase Separation and Morphology Development in Liquid Crystal/polymer Blends written by Domasius Nwabunma and published by . This book was released on 1999 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Photopolymerization-induced Crystallization in Relation to Solid-liquid Phase Diagrams of Blends of Blends of Poly(ethylene Oxide)/multi-functional Acrylate Monomers by : Soo Jeoung Park
Download or read book Photopolymerization-induced Crystallization in Relation to Solid-liquid Phase Diagrams of Blends of Blends of Poly(ethylene Oxide)/multi-functional Acrylate Monomers written by Soo Jeoung Park and published by . This book was released on 2008 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the present dissertation is to elucidate of the phenomenon of photopolymerization-induced phase transition (PIPT) in order to provide guidance to the fabrication of polymer photonic crystals via photolithography. The phenomenon of photopolymerization-induced phase separation and crystallization is a phase transformation process driven by photochemical reaction, in which the phase ordering occurs during the photo patterning. Although the reaction-induced phase separation is well investigated, the photopolymerization-induced crystallization is new in this field. First, the solid-liquid phase diagrams of the starting blends of polyethylene oxide (PEO)/multi-functional acrylate monomers have been established by means of differential scanning calorimetry and optical microscope. It was found that the PEO/acrylate systems reveal various coexistence regions including isotropic (I), the coexistence of crystal + liquid (Cr1+L2) and the crystal + crystal (Cr1+Cr2) gaps. A phase field theory pertaining to the solid-liquid phase transition in conjunction with the Flory Huggins theory for liquid-liquid phase separation has been developed to test with these experimental phase diagrams. The aforementioned coexistence regions have been further verified experimentally by probing the spatio-temporal emergence of crystalline structure and phase morphology using time-resolved optical microscopy following several temperature-quenches into these individual coexistence regions. The effects of molecular weight of PEO and acrylate arm topology of acrylate monomers on their blend phase diagrams have been explored.Guided by these established phase diagrams of the PEO/multi-functional acrylate blends, photopolymerization-induced crystallization experiments have been carried out at the isotropic temperatures slightly above the depressed melting points of PEO crystals corresponding to the liquidus line. The depressed melting curve shifts upward to the elevated temperatures and eventually surpasses the reaction temperature which in turn drives the system into the unstable gap triggering the photopolymerization-induced crystallization. Various crystalline phase morphologies including development of spherulites in the continuum of the isotropic region were observed in the crystal + liquid coexistence region. At higher reaction temperatures, above the melting temperature, viscous fingering (or fractal growth) takes place during photopolymerization, showing phase separated domains within these advancing viscous fingering structures. Finally, the study was extended to holographic photopolymerization that allows the reaction to occur predominantly in high intensity regions to create periodic patterns. Of particular interest is the growth of the hierarchical structures of PEO crystals and two-phase morphology within the stripes or interconnected channels and/or arrays of spheres.
Book Synopsis Interface Morphology and Phase Separation in Polymer Dispersed Liquid Crystal (Pdlc) Composites by : Ryan Scott Justice
Download or read book Interface Morphology and Phase Separation in Polymer Dispersed Liquid Crystal (Pdlc) Composites written by Ryan Scott Justice and published by . This book was released on 2006 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on both imaging and some small-angle scattering, the literature suggests the phase separation between the polymer and liquid crystal (LC) phases in polymer dispersed liquid crystal (PDLC) composites results in a pure LC phase with a sharp and smooth interface. In this work, based on analysis of similar data, this conventional picture is brought into question. Here, we examine the two-phase morphology in an acrylate-based system that develops during polymerization-induced phase separation. Using ultra-small and small angle x-ray scattering in corroboration with microscopy, this work analyzes the affects of LC loading, PDLC recipe, and sample processing on the developing morphology between the two phases. From these analyses, we find inconsistencies between the literature and our experiments regarding the impact of recipe constituents and sample processing on LC domain size. Further, we find that interfaces in PDLCs are seemingly much more disordered than generally appreciated.
Book Synopsis Phase Transitions in Polymers: The Role of Metastable States by : Stephen Z.D. Cheng
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
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :Uttandaraman Sundararaj Publisher :Ann Arbor, Mich. : University Microfilms International ISBN 13 : Total Pages :516 pages Book Rating :4.:/5 (319 download)
Book Synopsis Morphology Development During Polymer Blending by : Uttandaraman Sundararaj
Download or read book Morphology Development During Polymer Blending written by Uttandaraman Sundararaj and published by Ann Arbor, Mich. : University Microfilms International. This book was released on 1994 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Photoisomerization- and Photopolymerization-induced Phase Transitions in Mixtures of Photoresponsive Chromophores and Reactive Mesogens by : Namil Kim
Download or read book Photoisomerization- and Photopolymerization-induced Phase Transitions in Mixtures of Photoresponsive Chromophores and Reactive Mesogens written by Namil Kim and published by . This book was released on 2010 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Phase diagram of various blend systems containing photochromophores and reactive mesogenic diacrylate monomers has been constructed both experimentally and theoretically. Differential scanning calorimetry was commonly utilized to determine phase transition temperature, and theoretical curve was obtained by solving self-consistently the combined free energy of Flory-Huggins, Maier-Saupe, and phase field theory. Depending on the system, it exhibited various single and coexistence phases including crystal, nematic, crystal + isotropic, nematic + isotropic, crystal + nematic, and crystal + crystal. Guided by the phase diagram, we further investigated (i) self-motion of azobenzene chromophore (AC) in triacrylate (TA) solutions, (ii) photoisomerization-induced phase transition of liquid crystalline azobenzene (LCAC) and spiropyran (SP) chromophore in its mixtures with reactive mesogenic diacrylate (RMDA), and (iii) photopolymerization-induced phase separation of RMDA/low molecular weight liquid crystal (LMWLC) blends. Self-motion of AC single crystal in TA solution was investigated in relation to the solid-liquid phase diagram. Upon thermal quenching from the isotropic melt to the crystal + liquid gap, the concentration gradient that formed as the result of TA expulsion induced convective flows and generated spatial variability of surface tension usually responsible for Marangoni effect. A stationary rhomboidal crystal was also shown to swim upon irradiation with UV light due to mechanical torque generated by trans-cis isomerization. The trans-cis photoisomerization of LCAC not only exerted a dramatic effect on the mesophase transitions, but also on the stratification on the crystal morphology. The phase diagram of photoisomerized mixtures displayed a significant depression of nematic ordering. Meanwhile, spiropyran-merocyanine molecular shape change induced the I-N phase transition, which was infusible. Upon photopolymerization of RMDA/LMWLC blends, the homogeneous mixtures underwent phase separation. As the crystalline and nematic ordering of monomeric unit was frozen. LMWLC was dispersed in the continuum of isotropic or anisotropic networks. Phase diagram exhibited the broad immiscible regions. The phase diagram of annealed hyperbranched polymer/LMWLC was an upper azeotrope, exhibiting the coexistence of nematic + isotropic phase above the clearing temperature of neat LMWLC. With decreasing temperature a focal-conic fan shaped texture developed in the composition range of 63~93 wt %, suggestive of induced smectic phase in the mixture."--Abstract.
Book Synopsis Flow Induced Morphological Transitions in Polymer Blends Containing a Liquid Crystalline Polymer by : María de Jesús van Eijndhoven Rivera
Download or read book Flow Induced Morphological Transitions in Polymer Blends Containing a Liquid Crystalline Polymer written by María de Jesús van Eijndhoven Rivera and published by . This book was released on 1997 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Polymer Blend De-mixing and Morphology Development During Tube Flow by : Askar Karami
Download or read book Polymer Blend De-mixing and Morphology Development During Tube Flow written by Askar Karami and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work is an investigation of morphology and de-mixing of polymer blends during melt flow through a tube. Morphology is the relative size, shape and location of each distinguishable phase present in a polymer blend. De-mixing is the shear-induced migration of different types of polymers away from each other during the flow. Being able to tailor de-mixing during extrusion can potentially result in a new family of plastics waste recycling processes with mixed waste entering an extruder and separate streams of different polymer types leaving it. Also, control of morphology development can lead to the formation of layered structures without the need for two or more extruders and co-extrusion. These ideas formed the basis for a U.S. Patent. However, obtaining an understanding of the phenomena is critical to improving separations to a practical level. This thesis is directed at elucidating morphology development and de-mixing of polymer blends in the most simple process design: melt flow through a tube. The work had four objectives. The first was to design a process that would enable elucidation of both morphology and de-mixing along the tube. This was done by attaching a long segmented tube to a static mixer which in turn was attached to the end of a single screw extruder. At the conclusion of a run, the tube was quenched and disassembled to provide the needed samples. The second objective was to develop analytical methods to measure polymer composition in the samples. A mid-infrared spectrometer technique and a method based on the use of a differential scanning calorimeter were developed. The third objective was to use the above accomplishments to elucidate morphology development and polymer migration. Shear-induced migration was quantitatively shown in various polyethylene-polypropylene, polypropylene-nylon6 and polyethylene-nylon6 blends. The theoretical rate of viscous energy dissipation per unit length of the tube was used to show that the observed shear-induced migration was in accordance with the principle of energy minimization. The ratio of the viscosity of the dispersed phased to that of the continuous phase greatly influenced the morphology of polypropylene-nylon6 and polyethylene-nylon6 blends: a droplet-dispersed phase structure occurred at a high viscosity ratio whereas a multi-layer structure resulted at viscosity ratios near unity. Shear-induced deformation and coalescence contributed to formation of the multi-layer structure. Finally, the fourth objective was to investigate the effect of morphology development on viscosity measurement by capillary rheometry. The extruder-tube process was used as the rheometer. Morphology had a large impact on the value of the measured viscosity and viscosity-composition data were shown to be not readily fit by two mixing rule models: Lees' model and a sheath-core model. Greatly improved results were obtained by introducing a "shear-induced interlayer slip factor" into the sheath-core model.
Book Synopsis Phase Separation and Morphology of Polymer Blends in an Electric Field by : Jing Li
Download or read book Phase Separation and Morphology of Polymer Blends in an Electric Field written by Jing Li and published by . This book was released on 2003 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Phase Morphology and Orientation Development of Polymer Blends in Melt Processing by : Jinhai Yang
Download or read book Phase Morphology and Orientation Development of Polymer Blends in Melt Processing written by Jinhai Yang and published by . This book was released on 2008 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this dissertation, we studied phase morphology development of various polymer blends in both extrusion and melt spinning using scanning electron microscopy (SEM) assisted with appropriate etching techniques. Various processing conditions, for example shear or elongation rate, shear or elongation stress, and extrusion die length/diameter ratio were considered. The effects of material characteristics, such as viscosity ratio, miscibility and interfacial tension, were studied. To do this, polymer blends were carefully selected. One isotactic polypropylene was blended with two ethylene butene copolymers (EBM), which had different butene contents. One of the blends was miscible and the other was immiscible. The polypropylene was also blended two ethylene octene copolymers (EOM). The above blends had low interfacial tension and different viscosity ratios. One EBM was blended with two polyamide 12 (PA12) materials. These blends had high interfacial tension and different viscosity ratios. One maleic anhydride grafted ethylene octene copolymer was added into the EBM/PA12 blends to descrease their interfacial tension. Studies were focused on a phenomenon that the dispersed phases in these blends could coalesce into a surface layer in both extrusion and melt spinning. This process was controlled by viscosity ratio, interfacial tension and processing conditions. The orientation development of melt spun fibers of these blends was studied by both wide angle X-ray diffraction (WAXD) and birefringence techniques. The orientation was affected by both blend morphologies and solidification order of the blend individual phases. The phase, which solidifies later in the spinline, did not affect the orientation of the first solidified phase. However, the first solidified phase, if it was continuous phase, could largely suppress the orientation of the second solidified phase. Composite stress analysis explained the different orientation behaviors. Extrusion of a PA12 material through a capillary die coated with a EBM material was studied. The EBM coated die could largely increase the flow rates of the PA12 melt compared with a clean die. This behavior was explained by significant slippage between PA12 and EBM melts. A flow model was given to calculate the slippage speeds. Adding some maleic anhydride grafted ethylene octene copolymer into the EBM could largely suppress the interface slippage between PA12 and EBM."--Abstract.
Book Synopsis Effect of Temperature and Shear on Phase Separation in Liquid Crystalline Polymer/polycarbonate Blends by : Kam-Wa (Danny) Lee
Download or read book Effect of Temperature and Shear on Phase Separation in Liquid Crystalline Polymer/polycarbonate Blends written by Kam-Wa (Danny) Lee and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Morphology Development During the Phase Inversion of Immiscible Polymer Blends by : Nicole Danielle Bautista Lazo
Download or read book Morphology Development During the Phase Inversion of Immiscible Polymer Blends written by Nicole Danielle Bautista Lazo and published by . This book was released on 2000 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Liquid Crystals and Display Technology by : Morteza Sasani Ghamsari
Download or read book Liquid Crystals and Display Technology written by Morteza Sasani Ghamsari and published by BoD – Books on Demand. This book was released on 2020-10-07 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid crystals have attracted scientific attention for potential applications in advanced devices. Display technology is continuously growing and expanding and, as such, this book provides an overview of the most recent advances in liquid crystals and displays. Chapters cover such topics as nematic liquid crystals, active matrix organic light-emitting diodes, and tetradentate platinum(II) emitters, among others.
Book Synopsis Morphology Development of Immiscible Polymer Blends in Complex Flow Fields by : Brian Edward Priore
Download or read book Morphology Development of Immiscible Polymer Blends in Complex Flow Fields written by Brian Edward Priore and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Synopsis Extensional Flow Effects on Morphology Development in Liquid Crystalline Polymers by : John R. Dorgan
Download or read book Extensional Flow Effects on Morphology Development in Liquid Crystalline Polymers written by John R. Dorgan and published by . This book was released on 1998 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:
