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Polymer Phase (polymer + phase)
Selected AbstractsA New Donor,Acceptor,Donor Polyfluorene Copolymer with Balanced Electron and Hole Mobility,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007A. Gadisa Abstract A new alternating polyfluorene copolymer poly[2,7-(9,9-dioctylfluoren)- alt -5,5-(5,,8,-di-2-thienyl-(2,,3,-bis-(3,,-octyloxyphenyl)-quinoxaline))] (APFO-15), which has electron donor,acceptor,donor units in between the fluorene units, is synthesized and characterized. This polymer has a strong absorption and emission in the visible range of the solar spectrum. Its electroluminescence and photoluminescence emissions extend from about 560 to 900 nm. Moreover, solar cells with efficiencies in excess of 3.5,% have been realized from blends of APFO-15 and an electron acceptor molecule, a methanofullerene [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM). It has also been observed that electron and hole transport is balanced both in the pure polymer phase and in polymer/PCBM bulk heterojunction films, which makes this material quite attractive for applications in opto-electronic devices. [source] Highly magnetic latexes from submicrometer oil in water ferrofluid emulsionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006Franck Montagne Abstract The synthesis of functionalized submicrometer magnetic latex particles is described as obtained from a preformed magnetic emulsion composed of organic ferrofluid droplets dispersed in water. Composite (polystyrene/,-Fe2O3) particles were prepared according to a two-step procedure including the swelling of ferrofluid droplets with styrene and a crosslinking agent (divinyl benzene) followed by seeded emulsion polymerization with either an oil-soluble [2,2,-azobis(2-isobutyronitrile)] or water-soluble (potassium persulfate) initiator. Depending on the polymerization conditions, various particle morphologies were obtained, ranging from asymmetric structures, for which the polymer phase was separated from the inorganic magnetic phase, to regular core,shell morphologies showing a homogeneous encapsulation of the magnetic pigment by a crosslinked polymeric shell. The magnetic latexes were extensively characterized to determine their colloidal and magnetic properties. The desired core,shell structure was efficiently achieved with a given styrene/divinyl benzene ratio, potassium persulfate as the initiator, and an amphiphilic functional copolymer as the ferrofluid droplet stabilizer. Under these conditions, ferrofluid droplets were successfully turned into superparamagnetic polystyrene latex particles, about 200 nm in size, containing a large amount of iron oxide (60 wt %) and bearing carboxylic surface charges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2642,2656, 2006 [source] Particle formation under monomer-starved conditions in the semibatch emulsion polymerization of styrene.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Abstract Particle formation and particle growth compete in the course of an emulsion polymerization reaction. Any variation in the rate of particle growth, therefore, will result in an opposite effect on the rate of particle formation. The particle formation in a semibatch emulsion polymerization of styrene under monomer-starved conditions was studied. The semibatch emulsion polymerization reactions were started by the monomer being fed at a low rate to a reaction vessel containing deionized water, an emulsifier, and an initiator. The number of polymer particles increased with a decreasing monomer feed rate. A much larger number of particles (within 1,2 orders of magnitude) than that generally expected from a conventional batch emulsion polymerization was obtained. The results showed a higher dependence of the number of polymer particles on the emulsifier and initiator concentrations compared with that for a batch emulsion polymerization. The size distribution of the particles was characterized by a positive skewness due to the declining rate of the growth of particles during the nucleation stage. A routine for monomer partitioning among the polymer phase, the aqueous phase, and micelles was developed. The results showed that particle formation most likely occurred under monomer-starved conditions. A small average radical number was obtained because of the formation of a large number of polymer particles, so the kinetics of the system could be explained by a zero,one system. The particle size distribution of the latexes broadened with time as a result of stochastic broadening associated with zero,one systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3940,3952, 2001 [source] Effect of processing variables on the linear viscoelastic properties of SBS-oil blendsPOLYMER ENGINEERING & SCIENCE, Issue 12 2001F. J. Navarro Block copolymers, especially styrene-butadiene-styrene three-block copolymers (SBS), are recognized as especially effective asphalt modifiers because of their thermoplastic elastomeric properties. The concentration of copolymer, its ability to swell by the maltenic oils, and the processing variables are essential in the development of a three-dimensional network in the polymer-rich phase that enhances the vis-coelastic properties of these modified binders. This swollen polymer phase may influence the mechanical properties of the modified bitumens and synthetic binders. This paper deals with the influences that processing variables exert on the linear viscoelastic properties of oil/SBS mixtures in a wide range of temperatures. From the experimental results obtained we may conclude that most of the oil/SBS blends studied are highly structured thermoplastic gels above a critical SBS concentration that depends upon temperature, time of processing and surrounding atmosphere. [source] Nanostructured polyolefins/clay composites: role of the molecular interaction at the interfacePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2008Elisa Passaglia Abstract The extent of interphase interactions between polymer phase and inorganic particles is the driving force addressing the preparation/properties design in the field of the corresponding micro- and nanocomposites. In the case of preparation of nanocomposites based on polyolefins (POs) and inorganic compounds as potentially nanodispersed phase, the use of a PO with proper functional groups is necessary for the interface adhesion and stabilization of the nanostructured morphology. According to this approach, ethylene/propylene copolymers with a different propylene content were used for the preparation of nanocomposites through melt mixing with organophilic montmorillonites (OMMT). By taking into account the important role of functionalities grafted onto POs, two different synthetic approaches were compared here: (1) the dispersion of the inorganic filler was obtained by using previously functionalized POs bearing carboxylate groups as matrices; (2) the nanocomposites were prepared by performing contemporaneously the functionalization of POs (by using maleic anhydride (MAH) and/or diethyl maleate (DEM)) and the dispersion of the filler in a one-step process. The morphology of the nanocomposites as well as the variation of solubility and glass transition temperature (Tg) of the PO matrix were evaluated and tentatively discussed with reference to functionalization degrees, structure of PO, and preparation procedure. Copyright © 2008 John Wiley & Sons, Ltd. [source] Bioproduction of the aroma compound 2-Phenylethanol in a solid,liquid two-phase partitioning bioreactor system by Kluyveromyces marxianusBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Fang Gao Abstract The rose-like aroma compound 2-phenylethanol (2-PE) is an important fragrance and flavor ingredient. Several yeast strains are able to convert l -phenylalanine (l -phe) to 2-PE among which Kluyveromyces marxianus has shown promising results. The limitation of this process is the low product concentration and productivity primarily due to end product inhibition. This study explored the possibility and benefits of using a solid,liquid Two-Phase Partition Bioreactor (TPPB) system as an in situ product removal technique. The system applies polymer beads as the sequestering immiscible phase to partition 2-PE and reduce the aqueous 2-PE concentration to non-inhibitory levels. Among six polymers screened for extracting 2-PE, Hytrel® 8206 performed best with a partition coefficient of 79. The desired product stored in the polymer was ultimately extracted using methanol. A 3,L working volume solid,liquid batch mode TPPB using 500,g Hytrel® as the sequestering phase generated a final overall 2-PE concentration of 13.7,g/L, the highest reported in the current literature. This was based on a polymer phase concentration of 88.74,g/L and aqueous phase concentration of 1.2,g/L. Even better results were achieved via contact with more polymers (approximately 900,g) with the aqueous phase applying a semi-continuous reactor configuration. In this system, a final 2-PE concentration (overall) of 20.4,g/L was achieved with 1.4,g/L in the aqueous and 97,g/L in the polymer phase. The overall productivities of these two reactor systems were 0.38 and 0.43,g/L,h, respectively. This is the first report in the literature of the use of a polymer sequestering phase to enhance the bioproduction of 2-PE, and exceeds the performance of two-liquid phase systems in terms of productivity as well as ease of operation (no emulsions) and ultimate product recovery. Biotechnol. Bioeng. 2009; 104: 332,339 © 2009 Wiley Periodicals, Inc. [source] Thermodynamic characterization of hybrid polymer blend systemsPOLYMER ENGINEERING & SCIENCE, Issue 6 2009Amos Ophir A thermodynamic model was used to predict the morphology of hybrid multicomponent polymer blend systems. Two systems were studied, both including two noncompatible polymers, a third compatibilizer polymer and layered, organo-treated clays. The polar and nonpolar contributions of the surface energies of the components of the systems were calculated using measurements of the contact angles. The morphology of the multicomponent systems and the relative position of the organo-clays within them, were predicted by calculating the interaction energies between the different components of the system and evaluating these values according to the Vaia and Giannelis thermodynamic model for polymer melt intercalation in organically modified layered silicates. The experimental results show good correlation with the prediction that the organo-clays will have higher affinity to the compatibilizer polymer component situated at the interface between the two noncompatible blend components. In addition, the presence of the organo-clays in this interface was found to have a significant additional compatibilizing effect between the two polymer phases. The results presented in this work support the idea that hybrid formation via polymer melt intercalation depends mostly on energetic factors that can be determined from surface energies of polymers and organo-modified layered silicates, also in the case of multiphase polymer system. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | ||||||||||