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Artykuły w czasopismach na temat "Heterogeneous Polystyrene"

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Lemaire, Marc. "Heterogeneous asymmetric catalysis". Pure and Applied Chemistry 76, nr 3 (1.01.2004): 679–88. http://dx.doi.org/10.1351/pac200476030679.

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Examples of enantioselective catalysts, including homogeneous supported catalysts and biphasic liquid/liquid, are described and compared. In the case of asymmetric hydride transfer, polythiourea was proven to be more efficient for ruthenium-catalyzed reduction of arylketones, although the iridium complexes gave rise to higher ee when using amino sulfonamide bound to a polystyrene matrix. In the case of asymmetric reduction, the modification of the binap allows the formation of a polymer that could be used as a catalyst precursor and exhibits enantioselectivities as high as observed in solution, but easier to separate and recycle. Bisoxazoline bound to silica particules could also be used in copper-catalyzed asymmetric Diels-Alder reaction and cyclopropanation with selectivities similar to that obtained in solution.
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Barbosa, Antonio C. F., Marcelo R. Pace, Luciana Witovisk i Veronica Angyalossy. "A new method to obtain good anatomical slides of heterogeneous plant parts". IAWA Journal 31, nr 4 (2010): 373–83. http://dx.doi.org/10.1163/22941932-90000030.

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A new method is presented to prepare anatomical slides of plant materials including a combination of soft and hard tissues, such as stems with cambial variants, arboreal monocotyledons, and tree bark. The method integrates previous techniques aimed at softening the samples and making them thereby more homogeneous, with the use of anti-tearing polystyrene foam solution. In addition, we suggest two other alternatives to protect the sections from tearing: adhesive tape and/or Mayer’s albumin adhesive, both combined with the polystyrene foam solution. This solution is cheap and easy to make by dissolving any packaging polystyrene in butyl acetate. It is applied before each section is cut on a sliding microtome and ensures that all the tissues in the section will hold together. This novel microtechnical procedure will facilitate the study of heterogeneous plant portions, as shown in some illustrated examples.
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Malik, Muhammad Salman, Asif Ali Qaiser i Muhammad Ahmed Arif. "Structural and electrochemical studies of heterogeneous ion exchange membranes based on polyaniline-coated cation exchange resin particles". RSC Advances 6, nr 116 (2016): 115046–54. http://dx.doi.org/10.1039/c6ra24594c.

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Yu, Rongbing, Shupeng Zhang, Yuting Luo, Ruofei Bai, Jiangfang Zhou i Haiou Song. "Synthetic possibility of polystyrene functionalization based on hydroxyl groups of graphene oxide as nucleophiles". New Journal of Chemistry 39, nr 7 (2015): 5096–99. http://dx.doi.org/10.1039/c5nj00815h.

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Wang, Chia-Ying, i M. D. Ediger. "Lifetime of spatially heterogeneous dynamic domains in polystyrene melts". Journal of Chemical Physics 112, nr 15 (15.04.2000): 6933–37. http://dx.doi.org/10.1063/1.481319.

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Dong, Laura Beth, Salomon Turgman-Cohen, George W. Roberts i Douglas J. Kiserow. "Effect of Polymer Size on Heterogeneous Catalytic Polystyrene Hydrogenation". Industrial & Engineering Chemistry Research 49, nr 22 (17.11.2010): 11280–86. http://dx.doi.org/10.1021/ie1011905.

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Nair, Vipin A., Suni M. Mustafa i Sreekumar Krishnapillai. "Polystyrene Supported Manganese Complexes: Heterogeneous Catalysts for Oxidation Reactions". Journal of Polymer Research 10, nr 4 (2003): 267–73. http://dx.doi.org/10.1023/b:jpol.0000004629.53837.b3.

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Liang, Yeru, Luyi Chen, Dongyang Zhuang, Hao Liu, Ruowen Fu, Mingqiu Zhang, Dingcai Wu i Krzysztof Matyjaszewski. "Fabrication and nanostructure control of super-hierarchical carbon materials from heterogeneous bottlebrushes". Chemical Science 8, nr 3 (2017): 2101–6. http://dx.doi.org/10.1039/c6sc03961h.

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Super-hierarchical carbons with a unique carbonaceous hybrid nanotube-interconnected porous network were fabricated by utilizing well-defined carbon nanotube@polystyrene bottlebrushes as building blocks.
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Sharma, Saurabh, Yamini Yamini i Pralay Das. "Hydrogenation of nitroarenes to anilines in a flow reactor using polystyrene supported rhodium in a catalyst-cartridge (Cart-Rh@PS)". New Journal of Chemistry 43, nr 4 (2019): 1764–69. http://dx.doi.org/10.1039/c8nj04646h.

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The present methodology described the chemo-selective hydrogenation of various nitroarenes in a flow reactor under polystyrene supported rhodium in a catalyst-cartridge (Cart-Rh@PS) as a heterogeneous nano-catalyst.
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Hassan, Yusuf, Rosa Klein i Perry T. Kaye. "Synthesis and characterization of new chiral ketopinic acid-derived catalysts immobilized on polystyrene-bound imidazole". Ovidius University Annals of Chemistry 28, nr 1 (23.02.2017): 7–10. http://dx.doi.org/10.1515/auoc-2017-0002.

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Abstract Four new chiral ketopinic acid-derived catalysts were anchored on a polystyrene-bound imidazole via non-covalent bond. The resulting heterogeneous catalysts were successfully characterized using IR, SEM, and TGA analyses.
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Rozprawy doktorskie na temat "Heterogeneous Polystyrene"

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Noble, Kristen Felice. "Tailored Chain Sequences of Brominated Syndiotactic Polystyrene Copolymers via Post-Polymerization Functionalization in the Heterogeneous Gel State". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/93515.

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This dissertation demonstrates the preparation of blocky brominated syndiotactic polystyrene (sPS-co-sPS-Br) copolymers with tailored chain sequences using a simple, post-polymerization functionalization method conducted in the heterogeneous gel state, and investigates the effect of sPS reaction state and sPS/solvent gel morphology on the copolymer microstructure and thermal properties. Gel-state (Blocky) brominated copolymers were prepared from a 10 w/v% sPS/carbon tetrachloride (CCl4) gel and a 10 w/v% sPS/chloroform (CHCl3) gel in a matched set containing 6−32 mol% p-bromostyrene (Br-Sty) units. For comparison, a matched set of randomly brominated copolymers was prepared using a homogeneous solution-state (Random) reaction method and a set of brominated copolymers was prepared using a heterogenous powder-state (Powder) reaction method. The degree of bromination was evaluated using 1H nuclear magnetic resonance (NMR) spectroscopy. Powder-state bromination produced copolymers with a limited degree of functionalization of up to 12 mol% Br and required a threefold longer reaction time than the gel-state method conducted on the sPS/CHCl3 gel, demonstrating that the powder-state method is time-consuming and the dense sPS powder is incapable of producing copolymers with high Br-content. Microstructural characterization provided by 13C NMR spectroscopy, showed that bromination of sPS produces multiple peaks in the quaternary carbon region of the NMR spectrum, signifying through-bond communication between neighboring styrene and Br-Sty monomers. This work provides the first high-resolution comonomer sequencing of brominated sPS copolymers. Characterization of the quaternary carbon spectrum, assisted by band selective gradient heteronuclear multiple bond correlation (bsgHMBC) spectroscopy, electronic structure calculations, and simulated statistically random copolymer chains, revealed that each resonance peak could be assigned to a styrene or Br-Sty unit that exists in the center of a unique sequence of five monomers (i.e., a pentad) along the copolymer chain (e.g., ssssb where s = styrene and b = brominated styrene). Our comonomer sequencing method demonstrated that the Blocky and Powder copolymers have block-like character. Remarkably, the Blocky copolymers exhibit notably higher degrees of blockiness and larger fractions of sssss and bbbbb pentads at low Br contents (i.e., 32 mol% Br), relative to the Powder copolymers, confirming their blocky microstructure. Quenched films of the Blocky copolymers, analyzed using ultra-small-angle (USAXS) and small-angle X ray scattering (SAXS), show micro-phase separated morphologies that are reminiscent of conventional block copolymer phase behavior, supporting that the Blocky copolymers contain distinct segments of pure sPS and segments of randomly brominated sPS. Crystallization behavior of the copolymers, examined using differential scanning calorimetry (DSC), demonstrates that the Blocky copolymers are more crystallizable and crystallize faster at lower supercooling compared to their Random analogs. Simulations of blocky copolymers were developed based on the semicrystalline gel morphology to rationalize the effect of gel-state functionalization on copolymer microstructure and crystallization behavior. The simulations confirm that restricting the accessibility of the brominating reagent to monomers well removed from the crystalline fraction of the gel network produces copolymers with a greater prevalence of long runs of pure sPS that is advantageous for preserving desired crystallizability of the resulting blocky copolymers. To investigate the effect of sPS/solvent gel morphology on copolymer microstructure and crystallization behavior, the sPS/CCl4 and sPS/CHCl3 copolymers were compared directly. Characterization of the sPS/solvent gels using USAXS/SAXS, revealed that the gels exhibit different morphologies and average lamella thicknesses. Microstructural analysis showed that the sPS/CHCl3 copolymers contain larger fractions of sssss pentad and a greater degree of blockiness. The sPS/CHCl3 copolymers contain larger phase domains, supporting that these copolymers contain longer distinct segments of pure sPS and randomly brominated sPS in a multiblock-like microstructure. In addition, the sPS/CHCl3 copolymers are more crystallizable during conditions of rapid cooling and crystallize faster at low supercooling relative to their sPS/CCl4 analogs. Simulated average chains of the Blocky copolymers, generated from the empirical pentad sequence distributions, provide strong evidence that the runs of pure sPS in the Blocky copolymers originate from the crystalline stems within the crystalline lamellae. Thus, the simulations support that semicrystalline blocky brominated copolymers with tailored chain sequences, phase behavior, and crystallization properties and can be prepared simply by changing the gelation solvent.
Doctor of Philosophy
Block copolymers are a class of large molecules (polymers) that are made up of two or more chains (blocks) of different smaller units (monomers) linked together at one of each of the chain ends. When the monomers that make up each block have distinctly different chemical properties, the blocks may be capable of self-assembling into well-ordered physical structures, which give the block copolymer unique material properties that are different, and often better than the properties of the individual blocks alone (homopolymers). Block cop olymers have thus received tremendous attention with respect to controlled preparation, tailored structure development, and customized physical properties, for their potential use in self-assembled, nanostructured materials. Nevertheless, the generally difficult procedures and conditions required to make (polymerize) block copolymers with controlled sequences limits the scope of their commercial application. As an alternative to conventional polymerization methods, this dissertation demonstrates a comparatively simple physical method to make copolymers that contain significantly non-random (blocky) monomer sequences, starting with a homopolymer and using a reagent to modify units along the polymer chain. This post-polymerization method is conducted in the homopolymer’s gel state, in which segments of the homopolymer chains are effectively shielded from the reagent. The homopolymer, syndiotactic polystyrene (sPS), was used as a model to conduct a fundamentical investigation into the effects of the polymer reaction state, i.e., gel, solution, or powder, and the gel structure (morphology) on the copolymer structure and properties. The gel-state was found to produce copolymers with a high degree of modification and a greater degree of blockiness than the solution-state and powder-state. Copolymers prepared from the gel state exhibited properties that are characteristic of conventional block copolymers. Furthermore, using the gel-state method, blocky copolymers with tailored chain sequences and properties were prepared by simply changing the gel morphology. Thus, reaction in the gel-state is demonstrated as a simple physical approach to polymer design and synthesis that will be useful in the development of next-generation functionalized materials through the modification of lowcost commodity polymers. As an advancement to the manner in which nanostructured materials are created, these tailored materials will greatly enhance the convenience of block copolymers for a wide variety of applications including structural and biomechanical materials, and polymeric membranes for energy conversion and water purification systems.
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Fahs, Gregory Bain. "The Effect of Ionomer Architecture on the Morphology in Gel State Functionalized Sulfonated Syndiotactic Polystyrene". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97193.

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This dissertation presents a discussion of blocky and randomly functionalized sulfonated syndiotactic polystyrene copolymers. These copolymers have been prepared over a range of functionalization (from 2% to 10%) in order to assess the effect of the incorporation of these polar side groups on both the thermal behavior and morphology of these polymer systems. The two different architectures are achieved by conducting the reaction in both the heterogeneous gel-state to obtain blocky copolymers and in the homogeneous solution state to obtain randomly functionalized copolymers. In order to compare both the thermal properties and morphology of these two systems several sets of samples were prepared at comparable levels of sulfonation. Thermal analysis of these two systems proved that the blocky functionalized copolymers provided superior properties with regard to the speed and total amount of the crystalline component of sulfonated syndiotactic polystyrene. Above 3% functionalizion the randomly functionalized copolymer was no longer able to crystallize, whereas, the blocky functionalized copolymer is able to crystallize even at a functionalization level of 10.5% sulfonate groups. When considering the morphology of these systems even at low percentages of sulfonation it is clear that the distribution of these groups is different based on the amplitude of the signal measured by small angle x-ray scattering. Additionally, methods were developed to describe both the distribution of ionic multiplets, which varies between blocky and randomly functionalized systems, but also the distribution of crystals. At a larger scale ultra-small angle x-ray scattering was employed to attempt to understand the clustering of ionic multiplets in these systems. Randomly functionalized polymers should a peak that is attributed to ion clusters, whereas blocky polymers show no such peak. Additional studies have also been done to look at the analysis of crystallite sizes in these systems when there are multiplet polymorphs present, it was observed the polymorphic composition is drastically different. All of these studies support that these systems bear vastly different thermal behavior and possess significantly different morphologies. This supports the hypothesis that this gel-state heterogeneous functionalization procedure produces a much different chain architecture compared to homogeneous functionalization in the solution-state.
Doctor of Philosophy
Polymers are a class of chemicals that are defined by having a very large set of molecules that are chemically linked together where each unit (monomer) is repeated within the chemical structure. In particular, this dissertation focuses on the construction what are termed as "blocky" copolymers, which are defined by having two chemically different monomers that are incorporated in the polymer chain. The "blocky" characteristic of these polymers means that these two different monomers are physically segregated from each other on the polymer chain, where long portions of the chain that are of one type, followed by another section of the polymer that has the other type of monomer. The goal of creating this type of structure is to try to take advantage of the properties of both types of monomers, which can create materials with superior synergistic properties. In this case a hydrophobic (water hating) monomer is combined with a hydrophilic (water loving) chain. This hydrophobic component in the polymer is able to crystallize, which provides mechanical and thermal stability in the material by acting as a physical tether to hold neighboring chains together. With the other set of hydrophilic monomers, which in this case have an ionic component incorporated, we can now take advantage of this chemical components ability to aide in the transportation of ions. Transportation of ions is useful in a variety of commercially relevant applications, two of the most important applications of these ionic materials is in membranes that can be used to purify water or membrane materials in fuel cell technologies, specifically for proton exchange membranes. The focus of this research in particular was to create a simple synthesis technique that can create these blocky polymer chain architectures, which is done by performing the reaction while the polymer is made into a gel. The key to this is that the crystals within the gel act as a barrier to chemical reactions, creating conditions where we have substantial portions of the material that are able to be functionalized and the crystals within the material that are protected from being functionalized. By looking at the thermal characteristics, such as melting temperatures and amount of crystals within these systems we have seen that functionalizing these polymers in the heterogeneous gel state gives substantially better properties than functionalizing these materials randomly. Much like oil and water, incompatible polymer chains will phase separate from each other. In this case the hydrophobic and ionic components will phase separate from each other. The shape and distribution of these phase separated structure will dictate many of the material properties, which can be described by modeling the data collected from x-ray scattering experiments. All of this information will tell us based on the initial conditions that these polymers were created in, what properties should be expected based on the morphology and thermal behavior. This gives a better understanding of how to fine tune these properties based on the structure of the gel and chemical reaction conditions.
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Langhe, Deepak. "POLYMER CRYSTALLIZATION IN DROPLETS AND CONFINED LAYERS USING MULTILAYERED FILMS". Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1317931856.

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Fisher, Daniel C. "PREPARATION AND APPLICATION OF CATALYSTS FOR THE STEREOSPECIFIC REDUCTION AND PHOTOOXYGENATION OF OLEFINS IN CONTINUOUS OPERATIONS: A NOVEL METHOD FOR THE PRODUCTION OF ARTEMISININ". VCU Scholars Compass, 2017. https://scholarscompass.vcu.edu/etd/5159.

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Over the last two centuries, the discovery and application of catalysts has had a substantial impact on how and what chemicals are produced.Given their broad significance, our group has focused on developing new catalyst systems that are recoverable and reusable, in an attempt to reduce concomitant costs. Our efforts have centered on constructing a recyclable chiral heterogeneous catalyst capable of effecting asymmetric hydrogenations of olefins with high stereoselectivity. A class of phosphinoimidazoline ligands, developed by researchers at Boehringer-Ingelheim, known as BIPI ligands, have proven efficacious in the asymmetric reduction of alkenes. However, these chiral ligands are homogeneous and coordinated to precious metals, rendering them irrecoverable and expensive. To address these issues, our group has derivatized the BIPI ligand-metal complex and immobilized it to the surface of graphene oxide as well as polystyrene. Their efficacy and recyclability toward the asymmetric hydrogenation of a functionalized olefin have been evaluated. Another facet of our work has included developing a cost effective synthetic process to artemisinin, the gold standard drug in the treatment of malaria.As a natural product, artemisinin’s worldwide supply remains highly unpredictable, contributing to great price volatility.Combining the benefits of catalysis and the advantages of continuous flow chemistry, our research has sought to develop an economical approach to convert a biosynthetic precursor, artemisinic acid, to artemisinin in three chemical transformations. High-throughput experimentation allowed us to screen a prodigious number of catalysts and identify those effective in the asymmetric hydrogenation artemisinic acid to dihydroartemisinic acid, the first step in the transformation. This screening directed us to an inexpensive, heterogeneous ruthenium catalyst. The second step of the process includes the photooxygenation of dihydroartemisinic acid, which involves photochemically generated singlet oxygen. We have evaluated a commercially available heterogeneous photocatalyst packed in a transparent bed, surrounded by light emitting diodes in the continuous photooxygenation of dihydroartemisinic acid to dihydroartemisinic acid hydroperoxide. The third and final step, an acid induced hock cleavage, initiates an intricate cascading reaction that installs an endoperoxide bridge to deliver artemisinin. Our process afforded a 57% yield from dihydroartemisinic acid to artemisinin.
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Santos, Fábio Júnior Mota dos. "Espumas de poliestireno impregnadas com nanopartículas de ouro para a redução do p-nitrofenol". Universidade Estadual da Paraíba, 2017. http://tede.bc.uepb.edu.br/jspui/handle/tede/3026.

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There are countless researches related to the treatment of waste water because they contain large amounts of recalcitrant chemicals, such as p-Nitrophenol widely used in the industry in dyeing leather. Because it is a very toxic substance even at low concentrations, its total removal and / or transformation into other less polluting substances becomes an urgent environmental issue. Gold nanoparticles because they have great catalytic potential besides being non-toxic can somehow contribute to the minimization of the environmental effects caused by nitrophenols. Reactions using homogeneous catalysts are not very feasible in some cases, they present great difficulty during the separation of the catalysts from the rest of the reaction medium. In this context, this work aimed at the development of a catalyst based on gold nanoparticles impregnated in polystyrene foams an industrial waste, using thermally induced phase separation as the method of obtaining the same. It is then tested for catalytic reduction of p-Nitrophenol. The gold nanoparticles of different diameters were obtained using different synthesis conditions and characterized by spectrophotometry in the region of the visible for the size measurement, whereas for the already impregnated foams the characterization techniques used were the scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric (TG) analysis and thermogravimetric analysis (DTG). The catalyst was tested using as a model reaction the reduction of p-Nitrophenol to p-Aminophenol, the whole process was accompanied by UV-vis and what is concluded is a variation in the reaction velocities as a function of the variation of the particle size present in the foam and / or their concentrations therein.
Já são inúmeras as pesquisas relacionadas ao tratamento de águas residuais pelo fato de as mesmas conterem grandes quantidades de substancias químicas recalcitrantes, a exemplo do p-Nitrofenol muito utilizado na indústria no tingimento de couro. Por se tratar de uma sustância muito tóxica mesmo em baixas concentrações sua total remoção e/ou transformação em outras menos poluentes, torna-se uma questão ambiental urgente. As nanopartículas de ouro por apresentarem grande potencial catalítico além de não serem tóxicas, podem de alguma forma contribuir para a minimização dos efeitos agressivos ao ambiente causados por nitrofenóis. Reações que utilizam catalisadores homogêneos são pouco viáveis em alguns casos, apresentam grande dificuldade durante a separação do catalisados do restante do meio reacional. Nesse contexto esse trabalho objetivou o desenvolvimento de um catalisador a base de nanopartículas de ouro impregnadas em espumas de poliestireno um rejeito industrial, utilizando como método de obtenção para o mesmo a separação de fases induzida termicamente. Para então testa-lo na redução catalítica do p-Nitrofenol. As nanopartículas de ouro de diferentes diâmetros foram obtidas utilizando-se diferentes condições de síntese e caracterizadas através da espectrofotometria na região do visível para a aferição do tamanho, enquanto que para as espumas já impregnadas as técnicas de caracterização utilizadas foram a microscopia eletrônica de varredura (MEV), difração de raio-X (DRX), analise termogravimétrica (TG) a derivada da analise termogravimétrica (DTG). O catalisador foi testado utilizando como reação modelo a redução do p-Nitrofenol a p-Aminofenol, todo o processo foi acompanhado por UV-vis e o que se conclui é uma variação nas velocidades das reações em função da variação do tamanho de partículas presente na espuma ou/e de suas concentrações na mesma.
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Gittsegrad, Anna. "Heterogeneous Structural Organization of Polystyrene Fibers Prepared by Electrospinning". Thèse, 2018. http://hdl.handle.net/1866/20040.

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Wang, Chia-Ying. "Spacially heterogeneous dynamics in supercooled O-terphenyl and polystyrene melts /". 1999. http://www.library.wisc.edu/databases/connect/dissertations.html.

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Manz, Alyssa Sarah Jane Hennings. "Probing Heterogeneous Dynamics One Molecule at a Time: Polystyrene near the Glass Transition". Thesis, 2019. https://doi.org/10.7916/d8-ge1m-yv03.

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Polymeric systems near their glass transition are known to exhibit heterogeneous dynamics that evolve both over space and time, yet many of the underlying principles of these dynamics are still poorly understood. In this thesis, experimental single molecule studies aimed at uncovering the dynamics of polystyrene near its glass transition temperature are described. In a first approach, the influence of temperature on the timescales associated with dynamic heterogeneity – also referred to as exchange times – are identified by following the dynamics of a fluorescent perylene diimide probe embedded in a high-molecular weight polystyrene host. No clear influence on the lifetime of dynamics is found in the temperature regime Tg to Tg + 10 K. In a second study, heterogeneous dynamics are investigated in the context of molecular weight and fragility. In a similar experimental approach to that of the first study, two fluorescent dyes are utilized to report on the rotational dynamics of low- to high-molecular weight polystyrene hosts. In accordance with previous reports, the stretching exponent, β, is found to be correlated with the system’s molecular weight, even on a single molecule level. However, no clear correlation with the system’s exchange time was found. In a final study, several single molecule approaches aimed at uncovering the dynamics in confined polystyrene films are described. As no evidence for previously-described mobile surface molecules has been found, this final chapter is meant to provide a basis for future single molecule studies in confined systems.
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Thurau, Courtney T. "Physical aging and equilibrium dynamics of polystyrene and polycarbonate : the role of spatially heterogeneous dynamics /". 2002. http://www.library.wisc.edu/databases/connect/dissertations.html.

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Książki na temat "Heterogeneous Polystyrene"

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Alyssa Sarah Jane Hennings Manz. Probing Heterogeneous Dynamics One Molecule at a Time: Polystyrene near the Glass Transition. [New York, N.Y.?]: [publisher not identified], 2019.

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Części książek na temat "Heterogeneous Polystyrene"

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Davankov, Vadim, i Maria Tsyurupa. "Macroporous (Heterogeneous) Polystyrene Networks". W Hypercrosslinked Polymeric Networks and Adsorbing Materials, 71–116. Elsevier, 2011. http://dx.doi.org/10.1016/s0166-526x(11)56003-9.

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T. Varkey, Jaya. "Synthesis and Catalytic Activity Studies of Silver Nanoparticles Stabilized in Polymeric Hydro Gel". W Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97824.

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Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. But their stabilization towards agglomeration is a serious concern. Synthesized silver nanoparticles can be dispersed in polymeric hydrogel for stabilization and can be efficiently used in heterogeneous catalysis. Polystyrene crosslinked with 1, 6-hexanediol diacrylate can be suitably functionalized for catalytic activities. The nature of the support has a profound influence on the reactivity of the polymeric resin. A flexible support with optimum hydrophilic and hydrophobic balance enhanced the reactivity of the supporting system. Using this supported AgNPs catalytic reduction of Para-nitro phenol can be easily accomplished comparing to conventional method.
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Sheppard, R. C. "Introduction — a retrospective viewpoint". W Fmoc Solid Phase Peptide Synthesis. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780199637256.003.0005.

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The Chemical Society publication Annual Reports on the Progress of Chemistry for 1963 attempted to inform readers of all the highly significant advances in all the major fields of pure chemistry during that year. Fortunately, the section on peptide chemistry drew attention to a paper by R. B. Merrifield which had just been published in the Journal of the American Chemical Society: A novel approach to peptide synthesis has been the use of a chloromethylated polystyrene polymer as an insoluble but porous solid phase on which the coupling reactions are carried out. Attachment to the polymer constitutes protection of the carboxyl group (as a modified benzyl ester), and the peptide is lengthened from its amino-end by successive carbodiimide couplings. The method has been applied to the synthesis of a tetrapeptide, but incomplete reactions lead to the accumulation of by products. Further development of this interesting method is awaited. I remember thinking at the time that in this paper we had possibly seen both the beginning and the end of the interesting new technique of solid phase peptide synthesis. To many organic chemists, the described result was that anticipated—difficulty in bringing heterogeneous reactions to completion resulting in impure products. Both this and purification problems were expected to worsen as the chain length was increased beyond Merrifield’s tetrapeptide limit. In fact, I probably had at the time an inadequate appreciation of the difference between truly heterogeneous or surface reactions and those in the solvated gel phase. The latter approaches much more closely the solution situation. However, the new technique also flouted many of the basic principles of contemporary organic synthesis which required rigorous isolation, purification, and characterization regimes following each synthetic step. In Merrifield’s new technique, isolation consisted simply of washing the solid resin, there was no other purification of the products of each reaction, and little or no characterization of resin-bound intermediates was attempted. The first two of these are of course the important characteristics which give the method its speed and simplicity and contribute to its efficiency. Small wonder, though, that in many minds there was doubt about the future of the new technique.
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Streszczenia konferencji na temat "Heterogeneous Polystyrene"

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Zhao, Jun-Feng, i Han-Xiong Huang. "Migration of Nanoclay in PP/PS Blend and Effect of Its Localization on Cell Structure". W ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68660.

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In this work, the migration of clay in polypropylene/polystyrene (PP/PS) blend and the effect of its final localization on cell structure of microcellular foamed blend nanocomposites were studied. To observe the clay migration, a multilayered blend, alternatively superposed PS and PP/clay films with a thickness of 0.2 mm, was subjected to low shear flow. Batch foaming was performed on obtained blend nanocomposites to study the influence of the nanoclay localization on cell structure by using CO2 as the foaming agent. When subjected to flow, most clay dispersed in PP phase migrated into PS gradually. The migration of nanoclay caused smaller mean cell diameter and higher cell density to foamed PS. With the reduction of nanoclay content in PP phase, the cell density of PP foam decreased due to the reduction of heterogeneous nucleation sites and the mean cell diameter became smaller.
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Binkley, Michael, Andrew Ledbetter, Stefanie Shahan i J. Mark Meacham. "Reduced Order Modeling and Experimental Investigation of Acoustic Particle Manipulation in Complex 3D Geometries". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66904.

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A reduced order computational model and imaging experiments are presented as a combined method to investigate migration and trapping of microscale particles within an ultrasonic droplet generator. Use of two-dimensional (2D) cross-sectional representations of the three-dimensional (3D) device enables observation of acoustic focusing phenomena that are otherwise visually inaccessible. Our approach establishes relationships between system operating parameters and particle retention due to acoustic radiation forces that arise during atomization of heterogeneous particle suspensions. The droplet generator consists of a piezoelectric transducer for ultrasonic actuation, a resonant fluid-filled chamber, and an array of microscopic pyramidal nozzles. 2D visualization chips were produced through anodic bonding of glass to microfluidic reservoirs deep reactive ion etched in silicon. Open nozzle orifices of the 3D microarray were sealed in its 2D representation to facilitate filling and testing. Finite element analysis was used to model the harmonic response of the 2D assembly from 500 kHz to 2 MHz. The average nozzle tip pressure amplitude across the 2D array was then used to identify operating frequencies that correspond to optimal droplet ejection from the 3D device (ejection modes). The pressure field at these resonant frequencies predicts the equilibrium distribution of polymeric beads suspended in the reservoirs of the 2D chips. To qualitatively assess the accuracy of the model results, visualization experiments were performed at the first three ejection modes of the system (fn1 ≈ 620–680 kHz, fn2 ≈ 1.14 MHz, and fn3 ≈ 1.63 MHz) using 10 μm polystyrene beads. The model demonstrates a remarkable ability to capture the overall shape, as well as specific details of the terminal particle distributions, defined as the state with no further movement toward a pressure node or antinode. Finally, time course trials of acoustic focusing of heterogeneous particle suspensions were used to observe the influence of particle volume on the magnitude of the acoustic radiation force. A mixture of 5 μm and 20 μm diameter polystyrene beads was subjected to a standing acoustic field in the 2D chips. Particle position was recorded at 5 ms intervals until an equilibrium distribution was achieved. As expected, the larger beads focused much more rapidly than smaller beads, acquiring their final positions in seconds (versus 10s of seconds for the 5 μm particles). The method and results reported here serve as building blocks toward translation of an existing ultrasonic droplet generator into a high-throughput particle separation and isolation platform.
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Burra, K. G., P. Singh, N. Déparrois i A. K. Gupta. "Pyrolysis and CO2 Gasification of Composite Polymer Absorbent Waste for Syngas Production". W ASME 2019 Power Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/power2019-1884.

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Abstract Development of alternative carbonaceous sources for energy production is essential to alleviate the dependence on depleting fossil fuels which led to increasing atmospheric CO2 and thus global warming. While biomass utilization for energy and chemical production has been extensively studied in the literature, such studies on municipal solid wastes is difficult to interpret due to the heterogeneous nature of the waste. Understanding of the influence of individual components is necessary for comprehensive development of waste-to-energy pathway. One such waste that is complicated and has often been ignored in the literature is composite polymer absorbent material waste which can also be considered as a potential feedstock for thermochemical pathway of energy production. Composite polymer absorbent materials are ubiquitously used these days in the form of sanitary napkins, diapers, water blockers, fire blockers and surgical pads due to their high water-absorptive nature. Pyrolysis and CO2 gasification is ideal for such materials due to its versatile feedstock intake and uniform product output in the form of syngas with adjustable composition. CO2 gasification also provides the added benefit of CO2 utilization which provides carbon offset to this process. In the present study, a mixture of cellulose, absorbent material (sodium polyacrylate), polypropylene and polystyrene in a fixed proportion, to model approximate composition of a diaper, was examined for its pyrolysis and CO2 gasification capability for viable syngas production. The influence of individual components into the syngas yield from the composite waste gasification was also investigated. A fixed-bed, semi-batch reactor facility along with gas chromatography was employed to analyse the syngas yield and compositional evolution. Pyrolysis was done under nitrogen atmosphere and gasification was done under CO2 atmosphere. CO2 gasification provided net CO2 consumption which means a net reduction in carbon emissions per joule of energy produced. The sample was tested under four isothermal conditions of 973, 1073, and 1173 K to understand the impact of operational conditions on the syngas yield. Influence of individual component of the composite absorbent waste on the syngas yield and composition was also analyzed by comparing these syngas characteristics with that of the yield from gasification of its individual components separately at 1173 K. These investigations provided us with novel results on the behavior and capabilities of these composite polymer absorbent wastes and which opens up a new avenue towards efficient utilization of solid waste resources for sustainable energy production in the form of syngas which can also be used for various chemicals production such as methanol, gasoline and other petrochemical products.
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Raporty organizacyjne na temat "Heterogeneous Polystyrene"

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Afeworki, Mobae, i Jacob Schaefer. Mechanism of DNP-Enhanced Polarization Transfer Across the Interface of Polycarbonate/Polystyrene Heterogeneous Blends. Fort Belvoir, VA: Defense Technical Information Center, listopad 1991. http://dx.doi.org/10.21236/ada242570.

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