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Activated polymerization

Certain state highway authorities are studyiag the use of ftber-reiaforced polymers, typically thermosets such as epoxy or unsaturated polyester, for bridge constmction. On an even more futuristic scale, fiber optics that employ polymeric jacketing and, ia some cases, optically active polymeric cores, may someday be employed ia place of wines for home security systems, climate control, etc (10,91). [Pg.338]

Because this enzyme catalyzes the committed step in fatty acid biosynthesis, it is carefully regulated. Palmitoyl-CoA, the final product of fatty acid biosynthesis, shifts the equilibrium toward the inactive protomers, whereas citrate, an important allosteric activator of this enzyme, shifts the equilibrium toward the active polymeric form of the enzyme. Acetyl-CoA carboxylase shows the kinetic behavior of a Monod-Wyman-Changeux V-system allosteric enzyme (Chapter 15). [Pg.806]

It is interesting to note that all the new aromatic systems, as described, undergo displacement polymerizations in DMAC solvent by the K2CO3 method, except perfluoroalkylene [10] and amide activated polymerization [9], which were performed in NMP solvent. The displacement polymerization in DMAC solvent was carried out at 155-164°C. poly(aryl ether ketones) require less reaction time (3-6 h) than other aromatic systems for synthesis of polyethers [15]. Synthesis of the fluorinated polyether as reported by Irvin et al. [16] was carried out at room temperature for 16 h (Mw = 75,000), whereas the same polymer by Mercer et al. [17] was synthesized at 120°C for 17 h (Mw = 78,970). [Pg.37]

This relatively new trend in PCM manufacturing business amounts to creating a polymeric matrix out of the liquid or gaseous phase directly on the filler surface which has previously undergone special conditioning aimed at generating active polymerization sites on it. [Pg.42]

Acetyl-CoA carboxylase is an allosteric enzyme and is activated by citrate, which increases in concentration in the well-fed state and is an indicator of a plentiful supply of acetyl-CoA. Citrate converts the enzyme from an inactive dimer to an active polymeric form, having a molecular mass of several milhon. Inactivation is promoted by phosphorylation of the enzyme and by long-chain acyl-CoA molecules, an example of negative feedback inhibition by a product of a reaction. Thus, if acyl-CoA accumulates because it is not esterified quickly enough or because of increased lipolysis or an influx of free fatty acids into the tissue, it will automatically reduce the synthesis of new fatty acid. Acyl-CoA may also inhibit the mitochondrial tricarboxylate transporter, thus preventing activation of the enzyme by egress of citrate from the mitochondria into the cytosol. [Pg.178]

Wherever possible, we have sought a direct comparison of the reactivities of structurally related Crni and q-II alkyls with ethylene. For example, after having established the catalytic activity of complexes of the type [( Cri (L)2R] (see above), we showed that the isostructural neutral compounds Cp Crn(L)2R did not polymerize ethylene instead facile P-hydrogen elimination was observed. [3) This difference in reactivity was not due to the charge of the complexes. Thus, we have subsequently shown that neutral Cr J alkyls are also active polymerization catalysts. For example, Cp Cr I(THF)Bz2 and even anionic Li[Cp Cr H(Bz)3] (Bz = benzyl) polymerized ethylene at ambient temperature and pressure, while the structurally related CpCrD(bipy)Bz proved inert.[5]... [Pg.154]

The surfaces of some types of silica and alumina freed from adsorbed water contain acidic -OH groups. Ballard et al. (15) showed that these -OH groups react readily with transition metal alkyls giving stable compounds that are highly active polymerization catalysts for olefins. These systems are best described with reference to silica. [Pg.293]

Table VI. Effect of R m VO(OR)2Cl on catalyst activity. Polymerization conditions moiar ratio butadiene, propylene is 1.1, monomer concentration, 31 wt. % in -hexane reaction, — 50°C catalyst, 0.8 mmol VO(OR)2Cl phm, 6.0 mmol i-Bu3Al phm reaction time, 3 h. Data from Ref. 19. Table VI. Effect of R m VO(OR)2Cl on catalyst activity. Polymerization conditions moiar ratio butadiene, propylene is 1.1, monomer concentration, 31 wt. % in -hexane reaction, — 50°C catalyst, 0.8 mmol VO(OR)2Cl phm, 6.0 mmol i-Bu3Al phm reaction time, 3 h. Data from Ref. 19.
Colchicine is allelochemical from Colchicium genera, which binds the tubulin and prevents the mitosis (Fig. 2) Cytochalasin B, cell permeable fungal toxin from Helminthosporium dematiodeum, which inhibits cell division by blocking the active polymerization and formation of contractile actomyosin microfilaments, inhibit the germination of microspores (Roshchina, 2005a). Therefore, one mechanism of action of some allelochemicals from plants and... [Pg.30]

As noted above, turbidity and polymer weight concentration can be directly related (Cp = or, where t is the turbidity), and the proportionality constant may be determined experimentally (cf. Zackroff et al., 1980). Microtubule protein preparations, however, usually contain a fraction of protein that does not contribute to polymer formation, and the most likely interpretation is that this fraction is composed of assembly-incompetent tubulin and nontubulin protein contaminants (Gaskin et al., 1974 Zackroff et al., 1980). Note that Eq. (30) is based on the assumption that Co represents active, polymerization-competent protomer. If only a fraction y, less than one, is active, this equation must be corrected to give... [Pg.185]

Figure 3.19 Process for preparation of activated polymeric surfaces. (From Lee, P.H. et al.. Bioconjugate Chem., 13, 97-103, 2002. With permission.)... Figure 3.19 Process for preparation of activated polymeric surfaces. (From Lee, P.H. et al.. Bioconjugate Chem., 13, 97-103, 2002. With permission.)...
The silica-supported chromate can be activated directly to a very efficient ethylene polymerization catalyst by ethylene itself or by reduction under CO, to yield active Cr(ll) bisiloxy species, ](=SiO)2Cr] [8]. While the silsesquioxane Cr derivative on its own does not lead to an active polymerization catalyst under ethylene (albeit only low ethylene pressure were tested), the silsesquioxane chromate ester can yield an active polymerization catalyst by addition of methyl-aluminoxane as co-catalyst. Comparison between the two catalytic systems is therefore possible but suffers from the lack of molecular definition of the active homogeneous species obtained after activation with the alkylating agent (Scheme 14.11). [Pg.579]

Third, many solid state catalysts offered several active polymerization sites due to differences in the precise structure at and about the active sites. This resulted in an average stereoregular product being formed. [Pg.150]

Certain oxides, particularly clays and synthetic silica-alumina composites, are very active polymerization catalysts. They probably owe their activity to the presence of acidic hydrogen. [Pg.22]

Luen, D. Sengupta, A.K. (2000) Preparation and characterization of magnetically active polymeric particles (MAPPs) for complex environmental separations. Environ. Sci. Techn. 34 3276-3282... [Pg.602]

In transition metal chemistry, ligand variation has proven to be the key to obtaining highly active polymerization catalysts. In particular, sterically hindered monocationic alkyl complexes with an empty site seem to be well suited for polymerization. The steric bulk prevents (associative) -hydrogen transfer, while the positive charge destabilizes the free hydride and thus opposes (dissociative) /(-elimination. [Pg.148]

Davies-Coleman, M.T. Faulkner, D.J. Dubowchik, G.M. Roth, G.P. Poison, C. Fairchild, C. (1993) A new EGF-active polymeric pyridinium alkaloid from the sponge Calfyspongia fibrosa. J. Org. Chan., 58, 5925-30. [Pg.313]

In the kinetic experiments a special method of mixing was required. This revealed a further experimental variable order of addition. The initiator solution was frozen into the bottom of the NMR tube. Monomer was frozen on the upper walls of the tube. On initiation the monomer melted first and ran down onto the frozen initiator, the initiator solution thus melted into a high concentration of monomer. If however molten initiator solution was run on to frozen monomer the rate of polymerization was drastically reduced. The concentration of unreacted t-BuMg groups was also significantly reduced. The efficiency of initiation of active polymerization sites was much lower when this event occurs at high initiator and low monomer concentration. [Pg.195]

Research Focus Preparation of IV-substituted imide dialkyl-thiocarbamic acid esters as high-activity polymerization initiators. [Pg.317]


See other pages where Activated polymerization is mentioned: [Pg.103]    [Pg.195]    [Pg.6]    [Pg.274]    [Pg.130]    [Pg.309]    [Pg.276]    [Pg.286]    [Pg.291]    [Pg.292]    [Pg.300]    [Pg.323]    [Pg.285]    [Pg.215]    [Pg.473]    [Pg.507]    [Pg.26]    [Pg.169]    [Pg.170]    [Pg.171]    [Pg.571]    [Pg.572]    [Pg.572]    [Pg.519]    [Pg.273]    [Pg.576]    [Pg.141]    [Pg.164]   
See also in sourсe #XX -- [ Pg.576 ]

See also in sourсe #XX -- [ Pg.576 ]




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1.5- cyclooctadiene polymerization activity

Activated monomer enzymatic polymerization

Activation Energies of Propagation and Termination in Free Radical Polymerization

Activation energies anionic polymerizations

Activation energies cationic polymerizations

Activation energies step-growth polymerizations

Activation energies, step polymerization

Activation energy Ziegler—Natta polymerization

Activation energy anionic chain polymerization

Activation energy cationic chain polymerization

Activation energy emulsion polymerization

Activation energy olefin polymerization

Activation energy polymerization

Activation energy radical chain polymerization

Activation energy ring-opening polymerization

Activation energy stereoselective polymerization

Activation parameters polymerization

Activation temperature polymerization activity

Activation temperature polymerization kinetics

Activation volume selected polymerization reactions

Activator polymerization

Activator polymerization

Activators of anionic polymerization

Active Ester-Forming Polymeric Reagents

Active Species in the Polymerization of Cyclic Acetals

Active centres of polymerizations

Active centres of radical polymerizations

Active esters polymeric

Active in polymerizations

Active polymerization systems

Anionic chain polymerization activation parameters

Anionic polymerization active species

Anionic ring opening polymerization activators

Atom transfer radical polymerization activation rate constants

Atom transfer radical polymerization active copper complexes

Biologically Active Polymeric Displays

Biosynthesis of Monosaccharide Components, and Their Activation for Polymeric-Chain Formation

Catalytic activity, enzymes enzymatic polymerization reaction

Cationic coordination polymerization activated monomer

Cationic polymerization active species

Cationic polymerization covalent active species

Chain-growth polymerization laboratory activity

Cyclic acetal polymerization active sites

Discovery of Highly Active Molecular Catalysts for Ethylene Polymerization

Ethylene Polymerization Activity of Zr- and Ti-FI Catalysts

Ethylene polymerization active site concentration

Ethylene polymerization, with Lewis acid catalytic activity

Ethylene polymerizations, highly active

Ethylene polymerizations, highly active living

Ethylene polymerizations, highly active molecular catalysts

Exchange Activity (Immortal Polymerization)

Free radical addition polymerization activation energies

Free radical polymerization activation energies

Free radical polymerization biologically active polymers

Highly Active Ethene Polymerization Catalysts with Unusual Imine Ligands

Initiation of Polymerization at the Active Center

Isoprene polymerization active site distributions over kinetic

Lactams polymerization, activated monomer

Lactams polymerization, activated monomer mechanism

Living radical polymerization activation-deactivation processes

Living radical polymerization activator

Living radical polymerization active species

Monomers, optically active polymerization

Of anionic activated polymerization

Optically active hydrocarbons polymerizations

Organochromium catalysts polymerization activity

Oxirane polymerization active groups

Oxirane polymerization active sites

POLYMERIC SURFACE ACTIVE

POLYMERIC SURFACE ACTIVE AGENT

Plasma polymerization, electrically active

Plasma polymerization, electrically active polymers

Polymeric activated dextrans

Polymeric adsorbents versus activated carbons

Polymeric materials/polymers electrically active

Polymerization actinically activated

Polymerization activated monomer mechanism

Polymerization activators for

Polymerization active center

Polymerization active life

Polymerization activity

Polymerization activity

Polymerization activity cyclopentene

Polymerization by activated monomer mechanism

Polymerization monomer activation

Polymerization on activated ligands

Polymerization reversible activation

Polymerization surface activation

Polymerization with Two Active Species

Polymerization with activated monomer

Polymerization without Transfer and with One Active Species

Polymerization, activation

Polymerization, activation

Polymerization, activation anionic

Polymerization, activation cationic

Polymerization, activation coordination

Polymerization, activation deactivation

Polymerization, activation degree

Polymerization, activation equilibrium

Polymerization, activation experiments

Polymerization, activation industrial

Polymerization, activation ionic

Polymerization, activation kinetics

Polymerization, activation living

Polymerization, activation mechanisms

Polymerization, activation pressure effects

Polymerization, activation radiation induced

Polymerization, activation radical

Polymerization, activation regulated

Polymerization, activation ring-opening

Polymerization, activation solvent effects

Polymerization, activation spontaneous

Polymerization, activation statistics

Polymerization, activation structure-controlled

Polymerization, activation thermal

Polymerizations initiated by thermally activated donor-acceptor complexes

Propylene polymerization zirconocene precatalysts activated with

Radiation-activated polymerization

Radical chain polymerization activation parameters

Radical polymerization activation rate constants

Replacement in Transition Metal Alkyl Compounds and Polymerization Activity

Ring-opening polymerization activated monomer

Silica-alumina catalysts, active sites ethylene polymerization

Ziegler-Natta olefin polymerization active cationic species

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