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Reactive Solvent (reactive + solvent)
Selected AbstractsMicrowave-Assisted Kolbe-Schmitt Synthesis Using Ionic Liquids or Dimcarb as Reactive SolventsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009A. Stark Abstract The activation of relatively inert carbon dioxide as a building block for organic products is of interest from both ecological and chemical points of view. One of the few industrially relevant processes using CO2 is the Kolbe-Schmitt synthesis. Two strategies to obtain the carboxylated product 2,4-dihydroxybenzoic acid from resorcinol are presented: both Dimcarb and hydrogencarbonate- or methylcarbonate-based ionic liquids are employed as reactive solvents in a microwave-assisted reaction. Reaction optimization shows that the ionic liquids are more reactive than Dimcarb. However, Dimcarb offers advantages with regard to ecological aspects, such as the Global Warming and Human Toxicity Potential and the Cumulative Energy Demand, which were assessed as part of the process development. [source] Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent systemMACROMOLECULAR SYMPOSIA, Issue 1 2003Jaap Schut Abstract Syndiotactic polystyrene (sPS) is a new semi-crystalline thermoplastic which is believed to fill the price-performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy-amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy-amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic-thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy-amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy-amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7-9 min for low concentration blends, while it increases to 20-45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions. [source] DGEBA monomer as a solvent for syndiotactic polystyreneMACROMOLECULAR SYMPOSIA, Issue 1 2003Jaap Schut Abstract Syndiotactic polystyrene (sPS) has to be processed at high temperatures (i.e. >290°C due to its melting point of 270°C), which approaches its degradation temperature. We aim to facilitate the processing of sPS by lowering its melt temperature and viscosity with a curable epoxy/amine model system as reactive solvent, which will result in a thermoplastic-thermoset polymer blend. As a first step we therefore investigated the melting behaviour of sPS in epoxy monomer, established its phase diagram, and investigated the crystalline form of sPS in these mixtures. DGEBA epoxy monomer is found to be a solvent for syndiotactic polystyrene at temperatures above 220°C. The DGEBA-sPS phase diagram was established by means of DSC, on the basis of crystallization and melting peaks. The form of the curve in the phase diagram indicates that DGEBA is a poor solvent for sPS. In WAXS studies of blends only the , crystalline form was detected, not the , form, thus no sPS-DGEBA polymer-solvent compounds (clathrates) were detected. However, DGEBA can still serve as a monomer for improved processing as it depresses the crystallization temperature by 20 to 60 K upon addition of 20 to 90 wt% DGEBA respectively, while a 16 to 45 K melting peak depression can be observed by adding 20 to 90 wt% DGEBA. [source] Methylene as a possible universal footprinting reagent that will include hydrophobic surface areas: Overview and feasibility: Properties of diazirine as a precursorPROTEIN SCIENCE, Issue 12 2000Frederic M. Richards Abstract Methylene is one of, if not the, most reactive organic chemical known. It has a very low specificity, which makes it essentially useless for synthesis, but suggests a possible role in protein footprinting with special importance in labeling solvent accessible nonpolar areas, identifying ligand binding sites, and outlining interaction areas on protomers that form homo or hetero oligomers in cellular assemblies. The singlet species is easily and conveniently formed by photolysis of diazirine. The reactions of interest are insertion into C-H bonds and addition to multiple bonds, both forming strong covalent bonds and stable compounds. Reaction with proteins and peptides is reported even in aqueous solutions where the vast majority of the reagent is used up in forming methanol. Species containing up to 5 to 10 extra : CH2 groups are easily detected by electrospray mass spectroscopy. In a mixture of a 14 Kd protein and a noninteracting 1.7 Kd peptide, the distribution of mass peaks in the electrospray spectra was close to that expected from random modification of the estimated solvent accessible area for the two molecules. For analysis at the single residue level, quantitation at labeling levels of one 13CH2 group per 10 to 20 kDa of protein appears to be possible with isotope ratio mass spectroscopy. In the absence of reactive solvents, photolysis of diazirine produces oily polymeric species that contain one or two nitrogen atoms, but not more, and are water soluble. [source] Microwave-Assisted Kolbe-Schmitt Synthesis Using Ionic Liquids or Dimcarb as Reactive SolventsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2009A. Stark Abstract The activation of relatively inert carbon dioxide as a building block for organic products is of interest from both ecological and chemical points of view. One of the few industrially relevant processes using CO2 is the Kolbe-Schmitt synthesis. Two strategies to obtain the carboxylated product 2,4-dihydroxybenzoic acid from resorcinol are presented: both Dimcarb and hydrogencarbonate- or methylcarbonate-based ionic liquids are employed as reactive solvents in a microwave-assisted reaction. Reaction optimization shows that the ionic liquids are more reactive than Dimcarb. However, Dimcarb offers advantages with regard to ecological aspects, such as the Global Warming and Human Toxicity Potential and the Cumulative Energy Demand, which were assessed as part of the process development. [source] | ||||||||||