Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Blends (2)
- Coagulation driven phase separation (2)
- Miscibility (2)
- Modeling (2)
- Morphology (2)
-
- Phase separation (2)
- Phytochemicals (2)
- Actuators (1)
- Copolymerization (1)
- Crystal Growth From Melt (1)
- Crystalization behavior (1)
- Crystallisation (1)
- Crystallization kinetics (1)
- Diagrams (1)
- Dynamics (1)
- Foam (1)
- Free Energy (1)
- Gel permeation chromatography (1)
- Ginzburg-Landau Theory (1)
- Gradient cross-sectional morphology (1)
- Isomer/isomerization (1)
- LCP (1)
- Lattice models (1)
- Light (1)
- Light scattering (1)
- Liquid-crystalline polymers (LCP) (1)
- Melting (1)
- Mesoporous silica (1)
- Mixtures (1)
- Morphology development (1)
Articles 1 - 30 of 51
Full-Text Articles in Engineering
Conductive Behaviour In Relation To Domain Morphology And Phase Diagram Of Nafion/Poly(Vinylidene Co Triflouoroethylene) Blends, Nadzrinahamin Nazir, Namil Kim, Wilder Iglesias, Antal Jakli, Thein Kyu
Conductive Behaviour In Relation To Domain Morphology And Phase Diagram Of Nafion/Poly(Vinylidene Co Triflouoroethylene) Blends, Nadzrinahamin Nazir, Namil Kim, Wilder Iglesias, Antal Jakli, Thein Kyu
Thein Kyu
Electron and proton conductive properties of Nafion/poly(vinylidene fluroride)-co- trifluoroethylene (PVDF-TrFE) blends were investigated in relation to domain morphology guided by phase diagram using differential scanning calorimetry, polarized optical microscopy, and AC impedance analyzers. A theoretical phase diagram was established by self-consistently solving the combined free energy density of FloryeHuggins theory for liquid-liquid demixing and the phase field theory for crystal solidification. Nafion/PVDF-TrFE blends revealed an hourglass type phase diagram, consisted of single phase crystal (Cr1), liquid þ liquid (L1 þ L2) and crystal þ liquid (Cr1 þ L2) coexistence regions. Guided by the phase diagram, the co-continuous or dispersed droplet …
Influence Of Acrylate Arm Topology On Phase Diagrams Of Mixtures Of Multi-Arm Acrylate Photo-Curative Monomers And Nematic Liquid Crystals, Scott Meng, Hatice Duran, Thein Kyu
Influence Of Acrylate Arm Topology On Phase Diagrams Of Mixtures Of Multi-Arm Acrylate Photo-Curative Monomers And Nematic Liquid Crystals, Scott Meng, Hatice Duran, Thein Kyu
Thein Kyu
Phase equilibria of binary mixtures of liquid crystal and multiarm star acrylate derivatives have been established as a function of the number of acrylate arms by means of cloud point determination. Equilibrium phase diagrams of liquid crystal/multiarm acrylate derivatives have been calculated self-consistently in the framework of combined Flory−Huggins free energy of liquid−liquid demixing and Maier−Saupe free energy of nematic ordering. It was found experimentally that the phase diagram of the branched/star molecule/solvent shifts to elevated temperatures with an increasing number of acrylate arms. This movement of the coexistence line is attributed to the architectural effect contributing to the athermal …
Experimental And Theoretical Investigations Of Porous Structure Formation In Electrospun Fibers, Pratyush Dayal, Jing Liu, Satish Kumar, Thein Kyu
Experimental And Theoretical Investigations Of Porous Structure Formation In Electrospun Fibers, Pratyush Dayal, Jing Liu, Satish Kumar, Thein Kyu
Thein Kyu
The development of internal microstructure in electrospun fibers has been investigated both experimentally and theoretically. Various morphologies such as tubes, beads, and porous structures have been observed experimentally during electrospinning from amorphous polymer solutions such as poly(methyl methacrylate)/methylene chloride and poly(styrene)/tetrahydrofuran. The dynamics of electrospinning is modeled based on multiple virtual strands of beads connected by Maxwell's elements in a cylindrical coordinate system. Concurrently, spatiotemporal growth of the porous structure is calculated in the framework of Cahn−Hilliard time-evolution equation under the quasi steady state assumption coupled with the solvent evaporation rate equation. The coarse-grain simulation reveals the real-time formation of …
Role Of Crystal-Amorphous Interaction On Phase Equilibria Of Crystal/Amorphous Polymer Blends, Rushikesh Matkar, Thein Kyu
Role Of Crystal-Amorphous Interaction On Phase Equilibria Of Crystal/Amorphous Polymer Blends, Rushikesh Matkar, Thein Kyu
Thein Kyu
A self-consistent theory has been developed for determination of phase diagrams of a crystalline polymer solution. Although the original Flory diluent theory captures the liquidus line, the theory is incapable of accounting for the solidus line due to the inherent assumption of complete immiscibility of solvent in the solid crystal. The present theory considers all possible interactions involving amorphous-amorphous and crystal-amorphous interactions. The self-consistent solutions predict various phase diagrams involving liquid-liquid, pure solid, and liquid-solid coexistence regions bound by liquidus and solidus lines. In the limit of complete insolubility of solvent in neat solid crystal, the original Flory diluent theory …
Single Phase Blends Of Polycarbonate And Polmethyl Methacrylate, Thein Kyu, Jeanne Saldanha
Single Phase Blends Of Polycarbonate And Polmethyl Methacrylate, Thein Kyu, Jeanne Saldanha
Thein Kyu
Clear, transparent, single phase blends of polycarbonate and a polyalkyl methacrylate in which the alkyl radical contains from 1 to about 10 carbon atoms, and in which the polycarbonate and the polyalkyl methacrylate are miscible in all proportions are obtained. Polymethyl methacrylate (PMMA) is the preferred polyalkyl methacrylate. These blends may be prepared by dissolving the two polymers in a mutual solvent having a boiling point of at least about 30° C. and evaporating the solvent at a temperature of from about 30° C. to the boiling point of the solvent. The preferred evaporation temperatures are from about 45° C. …
Morphology Development In Main-Chain Liquid Crystalline Polymer Fibers During Solvent Evaporation, Pratyush Dayal, Andrew Guenthner, Thein Kyu
Morphology Development In Main-Chain Liquid Crystalline Polymer Fibers During Solvent Evaporation, Pratyush Dayal, Andrew Guenthner, Thein Kyu
Thein Kyu
A nonequilibrium thermodynamic approach has been developed for describing the emergence of fiber morphologies from a liquid crystalline polymer solution undergoing solvent evaporation, including fibrillar structures, concentric rings, and spiral structures. We utilized Matsuyama–Kato free energy for main-chain liquid crystalline polymer (MCLCP) solutions, which is an extension of Maier–Saupe theory for nematic ordering and incorporates a chain-stiffening, combined with Flory-Huggins free energy of mixing. Temporal evolution of the concentration and nematic order parameters pertaining to the above free energy density of liquid crystalline polymer solution was simulated in the context of time-dependent Ginzburg–Landau theory coupled with the solvent evaporation rate …
In Vitro Evaluation Of Anti-Oxidant And Anti Inflammatory Properties Of Genistein Modified Hemodialysis Membranes, Chandrasekaran Neelakandan, Teng Chang, Thomas Alexander, Linda Define, Michelle Evancho-Chapman, Thein Kyu
In Vitro Evaluation Of Anti-Oxidant And Anti Inflammatory Properties Of Genistein Modified Hemodialysis Membranes, Chandrasekaran Neelakandan, Teng Chang, Thomas Alexander, Linda Define, Michelle Evancho-Chapman, Thein Kyu
Thein Kyu
Genistein-modified poly(amide):poly(vinyl pyrrolidone) (PA:PVP/G) hemodialysis membranes have been fabricated by coagulation via solvent (dimethyl sulfoxide, DMSO)/nonsolvent (water) exchange. The antioxidant and anti-inflammatory properties of the unmodified PA:PVP membranes were evaluated in vitro using human blood. It was found that these unmodified PA:PVP membranes were noncytotoxic to peripheral blood mononuclear cells (PBMC) but raised intracellular reactive oxygen species (ROS) levels. Pure genistein (in DMSO solution) was not only nontoxic to PBMC, but also suppressed the ROS levels in a manner dependent on genistein dosage. A similar dose-dependent suppression of ROS was found in genistein-modified PA (i.e., PA/G) membranes. However, the PVP …
Preparation, Characterization, And Physical Properties Of Multiwall Carbon Nanotube/Elastomer Composites, Leon Perez, Manuel Zuluaga, Thein Kyu, James Mark, Betty Lopez
Preparation, Characterization, And Physical Properties Of Multiwall Carbon Nanotube/Elastomer Composites, Leon Perez, Manuel Zuluaga, Thein Kyu, James Mark, Betty Lopez
Thein Kyu
The present article describes preparation, characterization, and physical properties of nanoparticles-filled composites consisting of multiwall carbon nanotubes (MWCNT) and styrene-butadiene rubber and nitrile- butadiene rubber. The reinforcing MWCNT fillers were synthesized by chemical vapor deposition on iron and cobalt catalysts supported by calcium carbonate substrates. These MWCNT were further treated with nitric acid to produce hydroxyl and carbonyl functional groups on the carbon nanotubes (CNT) surfaces. Of particular importance is that these functionalized CNTs were found to exert profound influence on the elastomeric matrices, particularly the vulcanization activation energy, resistance to solvent swelling, enhanced glass transition temperature, and improved storage …
Phase Equilibria And Phase Separation Dynamics In A Polymer Composite Containing A Main-Chain Liquid Crystalline Polymer, Do Kim, Thein Kyu, Takeji Hashimoto
Phase Equilibria And Phase Separation Dynamics In A Polymer Composite Containing A Main-Chain Liquid Crystalline Polymer, Do Kim, Thein Kyu, Takeji Hashimoto
Thein Kyu
Various topological phase diagrams of blends of main-chain liquid crystalline polymer (MCLCP) and flexible polymer have been established theoretically in the framework of Matsuyama–Kato theory by combining Flory–Huggins (FH) free energy for isotropic mixing, Maier–Saupe (MS) free energy for nematic ordering in the constituent MCLCP, and free energy pertaining to polymer chain-rigidity. As a scouting study, various phase diagrams of binary flexible polymer blends have been solved self-consistently that reveal a combined lower critical solution temperature (LCST) and upper critical solution temperature (UCST), including an hourglass phase diagram. The calculated phase diagrams exhibit liquidus and solidus lines along with a …
Eutectic Mesophase Transitions And Induced Crystalline Phase In Mixtures Of Hexagonal Columnar Liquid Crystal And Mesogenic Diacrylate, Tsang-Min Huang, Raisa Talroze, Thein Kyu
Eutectic Mesophase Transitions And Induced Crystalline Phase In Mixtures Of Hexagonal Columnar Liquid Crystal And Mesogenic Diacrylate, Tsang-Min Huang, Raisa Talroze, Thein Kyu
Thein Kyu
Eutectic behavior and the induced crystalline phase in mixtures of hexagonal columnar liquid crystal, 2, 3, 6, 7, 10, 11-hexakis-(pentyloxy) triphenylene (HPTP)/reactive mesogenic diacrylate monomer, 4-(3-acryloyloxypropyloxy)-benzoic acid 2-methyl-1, 4-phenylene ester (RM257) have been investigated both experimentally and theoretically. To determine the theoretical phase boundaries, we combined the free energy of Flory−Huggins free energy for liquid−liquid demixing, Maier−Saupe free energy of nematic ordering, and Chandrasekhar−Clark free energy of hexagonal ordering. The calculated phase diagram of the HPTP/RM257 blend is essentially of a eutectic type that consists of isotropic (I), nematic (N), and hexagonal columnar (Colh) regions, and nematic + isotropic (N+I), …
Effects Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid Crystalline Azobenzene Chromophore And Its Blends With Mesogenic Diacrylate, N. Kim, Q. Li, Thein Kyu
Effects Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid Crystalline Azobenzene Chromophore And Its Blends With Mesogenic Diacrylate, N. Kim, Q. Li, Thein Kyu
Thein Kyu
Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and …
Dynamics Of Spherulitic Growth In Blends Of Polypropylene Isomers, Rujul Mehta, Thein Kyu
Dynamics Of Spherulitic Growth In Blends Of Polypropylene Isomers, Rujul Mehta, Thein Kyu
Thein Kyu
The spatiotemporal growth of spherulites in blends of isotactic polypropylene (iPP) and atactic polypropylene (aPP) isomers has been investigated theoretically with the time-dependent Ginzburg–Landau equation, which consists of a nonconserved crystal order parameter and a conserved compositional order parameter. In the description of the total free energy, a local free energy density in the form of an asymmetrical double well, signifying the metastability and latent heat of crystallization, is combined with a nonlocal free energy term representing the interface gradient. In addition, the Flory–Huggins free energy for mixing between iPP and aPP isomers has been employed to account for blend …
Collaborative Studies Of Thermo-Oxidative Degradation Of Styrene Isoprene Diblock Copolymer, Scott Meng, S. Kuchanov, Jingli Xu, Thein Kyu
Collaborative Studies Of Thermo-Oxidative Degradation Of Styrene Isoprene Diblock Copolymer, Scott Meng, S. Kuchanov, Jingli Xu, Thein Kyu
Thein Kyu
Mechanisms and dynamics of thermo-oxidative degradation of styrene-co-isoprene (SI) diblock at a temperature above the order–disorder transition temperature, Todt, have been investigated both experimentally and theoretically. The structural development of SI during degradation was monitored by optical microscopy, and the reduction of molecular weight and molecular weight distribution during the degradation was determined by gel permeation chromatography (GPC). The degradation process was modeled in the framework of a kinetic model based on the framework of the Flory principle. The theoretical predictions were compared with the GPC results. Fourier transformed infrared spectroscopy (FTIR) experiment was conducted in situ during the thermo-oxidative …
Effects Of Genistein Modification On Miscibility And Hydrogen Bonding Interactions In Poly(Amide)/Poly(Vinyl Pyrrolidone) Blends And Morphology Development During Coagulation, Chandrasekaran Neelakandan, Thein Kyu
Effects Of Genistein Modification On Miscibility And Hydrogen Bonding Interactions In Poly(Amide)/Poly(Vinyl Pyrrolidone) Blends And Morphology Development During Coagulation, Chandrasekaran Neelakandan, Thein Kyu
Thein Kyu
Miscibility characteristics of poly(amide):poly(vinyl pyrrolidone) (PA:PVP) blends containing a soybean-derived phytochemical called “genistein” have been investigated using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The occurrence of hydrogen bonding in the binary PA/genistein (PA/G) and PVP/genistein (PVP/G) pairs as well as their ternary blends has been confirmed by Fourier transformed infrared spectroscopy (FTIR). On the basis of DSC and POM data, the morphology phase diagram of PA:PVP/G blends is mapped out, which consisted of various coexistence regions such as isotropic, liquid + liquid, liquid + crystal, liquid + liquid + crystal, and solid crystal regions. Subsequently, PA:PVP membranes …
Miscibility Characterization In Relation To Phase Morphology Of Poly(Ether Sulfone)/Poly(Vinyl Pyrrolidone) Blends Containing A Phytochemical, Chandrasekaran Neelakandan, Thein Kyu
Miscibility Characterization In Relation To Phase Morphology Of Poly(Ether Sulfone)/Poly(Vinyl Pyrrolidone) Blends Containing A Phytochemical, Chandrasekaran Neelakandan, Thein Kyu
Thein Kyu
Miscibility and morphology of poly(ether sulfone)/poly(vinyl pyrrolidone) (PES/PVP) blends containing a crystalline phytochemical called mangiferin were investigated using differential scanning calorimetry (DSC), Fourier transformed infrared spectroscopy (FTIR), and polarized optical microscopy (POM). The binary blends of PES/PVP were found to be completely miscible. However, FTIR experiments revealed no spectral shift that is attributable to the miscibility of the PES/PVP pair, although the occurrence of hydrogen-bonding interactions can be confirmed in binary blends of both PES/mangiferin and PVP/mangiferin. The addition of mangiferin to the PES/PVP blends resulted in liquid-liquid phase separation as well as liquid-solid phase transition. However, the liquid-liquid phase …
Photochromism And Photopolymerization Induced Mesophase Transitions In Mixtures Of Spiropyran And Mesogenic Diacrylate, Namil Kim, Harris Lam, Thein Kyu
Photochromism And Photopolymerization Induced Mesophase Transitions In Mixtures Of Spiropyran And Mesogenic Diacrylate, Namil Kim, Harris Lam, Thein Kyu
Thein Kyu
A phase diagram of a binary mixture of photochromic molecule (spiropyran) and mesogenic diacrylate monomer has been established by means of differential scanning calorimetry and polarized optical microscopy. Subsequently, a theoretical phase diagram has been calculated by self-consistently solving the combined Flory−Huggins free energy for isotropic mixing, Maier−Saupe free energy for nematic ordering, and phase field free energy for crystal solidification. The phase diagram thus obtained consists of various coexistence regions involving single-phase crystals, pure nematic, crystal + liquid, crystal + nematic, and crystal + crystal coexistence gaps. Under UV irradiation, both SP and SP/RM257 mixtures showed the lowering trend …
Non-Birefringent Optical Adhesives And Films, Thein Kyu
Non-Birefringent Optical Adhesives And Films, Thein Kyu
Thein Kyu
The invention pertains generally to miscible polymer blends which can be used in optical applications, particularly in liquid crystal displays and optical adhesives, in that they are essentially birefiringence-free. The polymeric blend alloy includes a first polymer having an inherent positive birefringence and a second polymer having an inherent negative birefringence, the first and second polymers being soluble within each other to predefined limits. The polymer blend is an essentially birefringence-free film layer suitable for use in liquid crystal displays which has adequate mechanical properties, such as dimensional stability, permeability to water vapor, scratch-resistance and insensitivity to temperature, in that …
Crystalline-Amorphous Interaction In Relation To Phase Diagrams Of Binary Polymer Blends Containing A Crystalline Constituent, Pankaj Rathi, Tsang-Min Huang, Pratyush Dayal, Thein Kyu
Crystalline-Amorphous Interaction In Relation To Phase Diagrams Of Binary Polymer Blends Containing A Crystalline Constituent, Pankaj Rathi, Tsang-Min Huang, Pratyush Dayal, Thein Kyu
Thein Kyu
The present article describes an equilibrium theory for determining binary phase diagrams of various crystalline-amorphous polymer blends by taking into account the contributions from both liquid-liquid phase separation between the constituents and solid-liquid phase transition of the crystalline component. An analytical expression for determining a crystal-amorphous interaction parameter is deduced based on the solid-liquid transition, involving the solidus and liquidus lines in conjunction with the coexistence curve of an upper critical solution temperature type. Of particular importance is that the crystalline-amorphous interaction parameter can be determined directly from the melting point depression data. The present analysis is therefore different from …
Photopolymerization Induced Directional Crystal Growth In Reactive Mixtures, Soo Park, Pankaj Rathi, Thein Kyu
Photopolymerization Induced Directional Crystal Growth In Reactive Mixtures, Soo Park, Pankaj Rathi, Thein Kyu
Thein Kyu
Photopolymerization-induced crystallization has been demonstrated in blends of polyethylene oxide–diacrylate at temperatures above the depressed melting temperature of the crystalline component. Upon exposure to ultraviolet irradiation, the melting transition curve moves upward and eventually surpasses the reaction temperature, thereby inducing phase separation as well as crystallization. The present paper demonstrates the occurrence of directionally solidified interface morphologies of polymer crystals subjected to a photointensity gradient. The epitaxially grown seaweed or degenerate structures were observed at the circumference (low-intensity region) while the dense branched spherulites developed at the core high-intensity region.
Theoretical Modeling Of The Phase Separation Dynamics In Blends Of Reactive Monomers, Gregory Yandek, Thein Kyu
Theoretical Modeling Of The Phase Separation Dynamics In Blends Of Reactive Monomers, Gregory Yandek, Thein Kyu
Thein Kyu
Experimental observations of the dynamics of phase behavior for blends of reactive constituents, i.e. diglycidyl ether of bisphenol A (DGEBA), curing agent methylene dianiline (MDA), and a reactive liquid rubber (R45EPI), have been theoretically modeled by coupling system thermodynamics governed by a summation of the free energies of mixing and network elasticity with reaction kinetics and diffusion equations. Snap-shots of the temporal evolution of ternary phase diagrams have been established based on the self-condensation reactions of DGEBA-MDA and R45EPI as well as a cross-reaction between the two constituents forming a copolymer. Numerical solution of the proposed mean-field model provides good …
Solubilization Of Genistein In Poly(Oxyethylene) Via Eutectic Crystal Melting, Sasiwimon Buddhiranon, Thein Kyu
Solubilization Of Genistein In Poly(Oxyethylene) Via Eutectic Crystal Melting, Sasiwimon Buddhiranon, Thein Kyu
Thein Kyu
Solid–liquid phase diagrams of binary crystalline blends of genistein with poly(ethylene oxide) (PEO) and poly(ethylene glycol) (PEG) were established experimentally and theoretically based on the combined Flory–Huggins free energy of liquid–liquid phase separation and the phase field free energy pertaining to crystal solidification. The liquidus lines obtained self-consistently were found to agree well with trends of depressed crystal melting transitions in genistein/PEO and genistein/PEG blends, exhibiting eutectic phase behavior. Of particular importance is the lowering of the eutectic temperature of the genistein/PEO blend by about 60 °C upon switching to the genistein/PEG system. The occurrence of interspecies hydrogen bonding between …
Ionic Conductivity In Relation To Ternary Phase Diagram Of Polyethylene Oxide, Succinonitrile, And Lithium Bis(Trifluoromethane) Sulfonimide Mixtures, Mauricio Echeverri, Namil Kim, Thein Kyu
Ionic Conductivity In Relation To Ternary Phase Diagram Of Polyethylene Oxide, Succinonitrile, And Lithium Bis(Trifluoromethane) Sulfonimide Mixtures, Mauricio Echeverri, Namil Kim, Thein Kyu
Thein Kyu
In an effort to develop free-standing lithium battery membrane, binary and ternary phase diagrams of poly(ethylene oxide) (PEO), bis(trifluoromethane)sulfonimide (LiTFSI), and succinonitrile (SCN) (i.e., solid plasticizer) mixtures have been established by means of differential scanning calorimetry and polarized optical microscopy. The occurrence of hydrogen bonds and/or coordination bonds in each binary pair (PEO/SCN, SCN/LiTFSI, and PEO/LiTFSI) was examined using Fourier transform infrared spectroscopy. The binary PEO/LiTFSI mixture exhibits a eutectic phase diagram with the liquid + crystal coexistence region having various crystal forms of the lithium salt, whereas the SCN/LiTFSI blend shows a wide noncrystalline region, which is highly desirable …
Transport Controlled Pattern Photopolymerization In A Single-Component System, Scott Meng, Kumar Nanjundiah, Thein Kyu, Lalgudi Natarajan, Vincent Tondiglia, Timothy Bunning
Transport Controlled Pattern Photopolymerization In A Single-Component System, Scott Meng, Kumar Nanjundiah, Thein Kyu, Lalgudi Natarajan, Vincent Tondiglia, Timothy Bunning
Thein Kyu
The purpose of the present paper is to extend the concept of pattern photopolymerization-induced phase separation of a binary blend to a single-component system containing pure photoreactive monomers with a minute level of photoinitiators. The patterning formation process was simulated in the framework of Cahn−Hilliard equation coupled with the photoreaction kinetic equation. Unlike binary systems undergoing photopolymerization-induced phase separation driven by thermodynamic force, the mechanism of pattern formation in the single-component system is essentially a photoreaction-induced transport phenomenon. Of particular interest is the observation of polymer concentration profiles evolving from a sinusoidal wave to various truncated ones. On the basis …
Induced Smectic Phases In Phase Diagrams Of Binary Nematic Liquid Crystal Mixtures, Tsang-Min Huang, Kathleen Mccreary, Shila Garg, Thein Kyu
Induced Smectic Phases In Phase Diagrams Of Binary Nematic Liquid Crystal Mixtures, Tsang-Min Huang, Kathleen Mccreary, Shila Garg, Thein Kyu
Thein Kyu
To elucidate induced smectic A and smectic B phases in binary nematic liquid crystal mixtures, a generalized thermodynamic model has been developed in the framework of a combined Flory–Huggins free energy for isotropic mixing, Maier–Saupe free energy for orientational ordering, McMillan free energy for smectic ordering, Chandrasekhar–Clark free energy for hexagonal ordering, and phase field free energy for crystal solidification. Although nematic constituents have no smectic phase, the complexation between these constituent liquid crystal molecules in their mixture resulted in a more stable ordered phase such as smectic A or B phases. Various phase transitions of crystal–smectic, smectic–nematic, and nematic–isotropic …
Photopolymerization Induced Crystallization In Relation To Solid-Liquid Phase Diagram Of Poly(Ethylene Oxide)/Diacrylate Monomer Blends, Soo Park, Thein Kyu
Photopolymerization Induced Crystallization In Relation To Solid-Liquid Phase Diagram Of Poly(Ethylene Oxide)/Diacrylate Monomer Blends, Soo Park, Thein Kyu
Thein Kyu
Phase diagrams of blends of poly(ethylene oxide) (PEO)/diacrylate (DA) monomer have been established by means of differential scanning calorimetry and optical microscopy. A phase field theory based on the combination of the phase field free energy of crystal solidification and the Flory−Huggins theory for liquid−liquid phase separation has been developed that is capable of predicting various coexistence regions of the binary crystalline PEO/DA blends, viz., isotropic (I), the coexistence of crystal + liquid (Cr1 + I), crystal + crystal (Cr1 + Cr2), and the single phase crystal (Cr) regions. These aforementioned coexistence regions have been further verified experimentally by probing …
Phase Diagrams Of Binary Crystalline Polymer Blends, Rushikesh Matkar, Thein Kyu
Phase Diagrams Of Binary Crystalline Polymer Blends, Rushikesh Matkar, Thein Kyu
Thein Kyu
A thermodynamically self-consistent theory has been developed to establish binary phase diagrams for two-crystalline polymer blends by taking into consideration all interactions including amorphous-amorphous, crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The present theory basically involves combination of the Flory-Huggins free energy for amorphous-amorphous isotropic mixing and the Landau free energy of polymer solidification (e.g., crystallization) of the crystalline constituents. The self-consistent solution via minimization of the free energy of the mixture affords determination of eutectic, peritectic, and azeotrope phase diagrams involving various coexistence regions such as liquid-liquid, liquid-solid, and solid-solid coexistence regions bound by liquidus and solidus lines. To validate the …
Three-Dimensional Switchable Photonic Crystals Via Various Optical Wave Interference Techniques, Gregory Yandek, Scott Meng, Grigori Sigalov, Thein Kyu
Three-Dimensional Switchable Photonic Crystals Via Various Optical Wave Interference Techniques, Gregory Yandek, Scott Meng, Grigori Sigalov, Thein Kyu
Thein Kyu
A theoretical study has been undertaken to elucidate the three‐dimensional pattern formation during holographic polymer‐dispersed liquid crystal fabrication employing various optical wave interference techniques. Initially miscible mixtures of nematic liquid crystal and reactive multifunctional monomer with a photosensitive initiator were exposed to geometrically arranged interfering beams of light, producing a spatially dependent intensity distribution within the sample. To mimic the spatio‐temporal evolution of periodic photonic structures in three dimensions, the time‐dependent Ginzburg–Landau Model C equations, coupled with spatially variant reaction rate equations, have been solved numerically incorporating the local free energy densities pertaining to isotropic mixing, nematic ordering, and network …
Holographic Photo-Polymerization Induced Phase Separation In Reference To The Phase Diagram Of A Mixture Of Photo-Curable Monomer And Nematic Liquid Crystal, Scott Meng, Thein Kyu, Lalgudi Natarajan, Vincent Tondiglia, Richard Sutherland, Timothy Bunning
Holographic Photo-Polymerization Induced Phase Separation In Reference To The Phase Diagram Of A Mixture Of Photo-Curable Monomer And Nematic Liquid Crystal, Scott Meng, Thein Kyu, Lalgudi Natarajan, Vincent Tondiglia, Richard Sutherland, Timothy Bunning
Thein Kyu
Theoretical investigation on pattern photopolymerization has been undertaken in various coexistence regions of a mixture of photocurable monomer and nematic liquid crystal. The phase diagram of the mixtures is constructed in accordance with a combined Flory−Huggins (FH) free energy of isotropic mixing and the Maier−Saupe (MS) free energy of nematic ordering. The pattern formation dynamics of holographic photopolymerization has been explored in conjunction with the phase diagram of the starting mixture of monomer and nematic liquid crystal. To mimic the evolution of holographic structure, the combined FH and MS free energy is incorporated into the time-dependent Ginzburg−Landau (model C) equations …
Effect Of The Chemical Characteristics Of Mesoporous Silica Mcm-41 On Morphological, Thermal, And Rheological Properties, Leon Perez, Juan Lopez, Victor Orozco, Thein Kyu, Betty Lopez
Effect Of The Chemical Characteristics Of Mesoporous Silica Mcm-41 On Morphological, Thermal, And Rheological Properties, Leon Perez, Juan Lopez, Victor Orozco, Thein Kyu, Betty Lopez
Thein Kyu
Mesoporous silica nanoparticles (MCM-41) with an average diameter of ∼ 20 nm were synthesized by a sol-gel method using binary surfactant system. Polystyrene (PS) composites containing mesoporous silica nanoparticles were prepared by in situ polymerization of styrene monomers. Similar in situ polymerized PS composites were prepared based on the modified silica functionalized with methyl and vinyl groups. The effects of silylation on thermal and rheological properties of the PS/silica composites are investigated. Of particular importance is that the in situ polymerization of monomers within the mesoporous silica may trap some polymer chains, if not all, thereby affording a greater physical …
Morphology Development In Polymer Fibers Undergoing Solvent/Non-Solvent Exchange, Pratyush Dayal, Thein Kyu
Morphology Development In Polymer Fibers Undergoing Solvent/Non-Solvent Exchange, Pratyush Dayal, Thein Kyu
Thein Kyu
The solvent/non-solvent interchange across the fiber surface affects the morphology of the fiber in various ways. In this paper, simulations have been performed to elucidate the diverse morphologies obtained during spinning of polymer fibers under the presence of a non-solvent. The proposed model deals with a ternary system derived from Cahn-Hilliard equation, alternatively known as Time Dependent Ginzburg Landau-TDGL model B equation, involving the spatio-temporal evolution of concentration order parameter. Depending on the coexistence region of the ternary phase diagram, various fiber morphologies including concentric bands, internal microfibrillar structures, and porous structures were discerned. It may be inferred that the …