177,838 research outputs found
The synthesis and properties of some well-defined fluorinated polymers
No full textThis thesis describes studies directed to the ring opening metathesis polymerisation (ROMP) of some fluorinated compounds using a range of well-defined initiators. Chapter 1 reviews some general aspects of olefin metathesis and ring opening metathesis polymerisation of relevance to the work described in this thesis. Topics such as piezo- and pyro-electricity and optical and electrical properties of conjugated polymers are introduced and these receive more detailed attention later in the thesis. Chapter 2 describes the synthesis, characterisation and properties of . poly(bis(trifluororaethyl)norbomadiene) in detail. The use of various initiating systems that have been used previously and the effect they have on the tacticity of the resulting polymer raicrostructure are discussed. The latter part of this chapter reviews some of the current thinking concerning the detailed mechanistic aspects of this polymerisation. Chapter 3 reviews attempts directed to an improvement in tacticity control in the synthesis of poly(bis(trifluoromethyl)norbomadiene). The synthesis and activity of the new well-defined initiators used in these studies are reported. It is shown that varying the nature of the ancillary Ligands surrounding the metal centre can have a dramatic influence on the tacticity of the resulting polymer. Chapter 4 reports studies directed to an examination of the limits of the well controlled synthesis of poly(bis(trifluoromethyl)norbornadiene). The syntheses of high trans and high cis, highly tactic poly(bis(trifluoromethyl)norbornadiene samples using well-defined initiating systems are described. It is shown that by varying the monomerinitiator ratio, samples with a wide range of molecular weights can be achieved and these are reported. Chapter 5 describes experiments concerning the ROMP of fluorinated monomers containing six membered rings. In particular ROMP studies of the monomers, 2,3-bis(trifluoromethyl)bicyclo[2.2.2]octa-2,5-diene . and 2,3- (tetrafluorobenzo)bicyclo[2.2.2]octatriene are described finally, Chapter 6 provides a summary of the work reported and outlines some ideas for future studies
Node types in the Shape Up Somerville (SUS) and Romp & Chomp (R&C) discussion networks.
No full textNode types in the Shape Up Somerville (SUS) and Romp & Chomp (R&C) discussion networks.</p
Shape Up Somerville (SUS) and Romp and Chomp (R&C) steering committee network metrics.
No full textShape Up Somerville (SUS) and Romp and Chomp (R&C) steering committee network metrics.</p
Demographics and affiliation information of survey participants from Shape Up Somerville (SUS) and Romp & Chomp (R&C).
No full textDemographics and affiliation information of survey participants from Shape Up Somerville (SUS) and Romp & Chomp (R&C).</p
High-Load, Hybrid Si-ROMP Reagents
No full textThe combination of norbornenyl-tagged (Nb-tagged) silica particles and functionalized Nb-tagged monomers for the generation of hybrid Si-ROMP reagents and scavengers is reported. Specifically Si-ROMP-derived bis-acid chloride, dichlorotriazine and triphenylphosphine scavenger/reagents have been grafted from the surface of silica particles utilizating surface-initiated, ring-opening metathesis polymerization (ROMP). These hybridpolymeric materials combine the physical properties of current immobilized silica reagents and represent a key advancement in load by merging the inherent tunable properties of the ROMP-derived oligomers with silica supports for application in parallel synthesis
High-Load, Hybrid Si-ROMP Reagents
No full textThe combination of norbornenyl-tagged (Nb-tagged) silica particles and functionalized Nb-tagged monomers for the generation of hybrid Si-ROMP reagents and scavengers is reported. Specifically Si-ROMP-derived bis-acid chloride, dichlorotriazine, and triphenylphosphine scavenger/reagents have been grafted from the surface of silica particles utilizing surface-initiated, ring-opening metathesis polymerization (ROMP). These hybrid polymeric materials combine the physical properties of current immobilized silica reagents and represent a key advancement in load by merging the inherent tunable properties of the ROMP-derived oligomers with silica supports for application in a parallel synthesis
Pensioenen en AOW geen onderwerp voor SER
No full textHet kabinet heeft zijn crisisplannen gepresenteerd en het meest pijnlijke onderdeel - geleidelijke verhoging van de pensioenleeftijd naar 67 jaar - is voorlopig doorgeschoven naar de overlegtafel in de SER. Volgens de Amsterdamse economen Beetsma en Romp is dit gezelschap niet geschikt, omdat het debat over het pensioenstelsel bij uitstek gaat om toekomstige, ongeboren generaties en vakbonden en werkgevers meer oog hebben voor hun eigen vergrijsde leden dan voor de toekomstige generaties
ROMP-based polymer composites and biorenewable rubbers
No full textThis research is divided into two related topics. In the first topic, the synthesis and characterization of novel composite materials reinforced with MWCNTs by ring-opening metathesis polymerization (ROMP) is reported for two ROMP based monomers: dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB). Homogeneous dispersion of MWCNTs in the polymer matrices is achieved by grafting norbornene moieties onto the nanotube surface. For the DCPD-based system, the investigation of mechanical properties of the composites shows a remarkable increase of tensile toughness with just 0.4 wt % of functionalized MWCNTs (f-MWCNTs). To our knowledge, this represents the highest toughness enhancement efficiency in thermosetting composites ever reported. DMA results show that there is a general increase of thermal stability (rg) with the addition of f-MWCNTs, which means that covalently bonded f-MWCNTs can reduce the local chain mobility of the matrix by interfacial interactions. The ENB system also shows significant enhancement of the toughness using just 0.8 wt % f-MWCNTs. These results indicate that the ROMP approach for polyENB is also very effective. The second topic is an investigation of the biorenewable rubbers synthesized by the tandem ROMP and cationic polymerization. The resin consists of a norbornenyl-modified linseed oil and a norbornene diester. Characterization of the bio-based rubbers includes dynamic mechanical analysis, tensile testing, and thermogravimetric analysis. The experimental results show that there is a decrease in glass transition temperature and slight increase of elongation with increased diester loading
ROMP-Facilitated Methodologies and Automated Library Development of Thiadiazepin-1,1-dioxide-4-ones
No full textThe use of ring-opening metathesis polymerization (ROMP) for polymer-assisted solution phase (PASP) synthesis is described herein. Multiple ROMP-based strategies will be discussed in the scope of this dissertation. These include the development and application of a multifaceted oligomeric phosphate as a facilitated leaving group in both SN2 and SN2´ processes, as well as an in-situ generated sequestration reagent. We also investigate the use of ROMP in an atom-economical approach to generate a diverse collection of cyclic sulfonamides (sultams) whereby a vanishing support protocol imparts a traceless, chromatography-free synthesis of these motifs. Also highlighted within is the ability to use ROMP technology to aid in the development of higher-loading magnetic nanoparticles for the purpose of supported catalysis. These cobalt-based ROMPgel nanoparticles were subsequently doped with Pd and demonstrated for use in several Suzuki-Miyaura coupling reactions. The nanoparticles were conveniently reclaimed via external magnetic field and recycled for later use. Lastly, we present the design, validation, and completion of a 225-member library of thiadiazepin-1,1-dioxide-4-ones using both solution- and polymer-assisted solution phase protocols. The library was validated and conducted on an automated parallel synthesis platform in which a facile, two-step diversity-rendering sequence was performed
End-Functionalized ROMP Polymers for Biomedical Applications
No full textWe present two novel allyl-based terminating agents that can be used to end-functionalize living polymer chains obtained by ring-opening metathesis polymerization (ROMP) using Grubbs’ third generation catalyst. Both terminating agents can be easily synthesized and yield ROMP polymers with stable, storable activated ester groups at the chain end. These end-functionalized ROMP polymers are attractive building blocks for advanced polymeric materials, especially in the biomedical field. Dye labeling and surface coupling of antimicrobially active polymers using these end-groups were demonstrated
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