Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Alkylation pendant groups

The cured or fully imidized polyimide, unlike the poly(amic acid), is insoluble and infusible with high thermooxidative stability and good electrical-insulation properties. Thermoplastic polyimides that can be melt processed at high temperatures or cast in solution are now also available. Through an appropriate choice of the aromatic diamine, phenyl or alkyl pendant groups or main-chain aromatic polyether linkages can be introduced into the polymer. The resulting polyimides are soluble in relatively nonpolar solvents. [Pg.57]

Paraffinic oils contain not only high levels of naphthenic rings but also higher levels of alkyl pendant groups, unsaturated hydrocarbon pendant groups, and, most important, fewer naphthenic groups per molecule. Pure paraffins from refined petroleum condense out as wax. [Pg.459]

Almost all of the rigid-rod polymers with flexible side branches have been prepared from monomer s substituted regular ly and laterally by either n-alkoxy " or n-alkyl pendant groups. [Pg.477]

Paraffinic oils contain high levels of naphthenic rings but also higher levels of alkyl pendant groups, unsaturated hydrocarbon pendant... [Pg.442]

Ordering of a PU film presents some restrictions on the chemical nature of the molecules. The molecules will typically need to be made amphiphilic by attaching either pendant nonpolar (e.g., alkyl) groups to yield a hydrophobic end, or pendant polar (e.g., carboxylic acid) or even ionic (e.g., carboxylate anion) groups to make a hydrophilic end, complicating the synthetic task. Further, the pendant groups may have a cross section that is not well matched with the size of the electroactive... [Pg.41]

On the basis of this simple orbital picture, we can also consider the effect of alternative alkene pendant groups R in the catalytic propagation reaction (4.105). In the case of propylene (R = CH3), for example, one can envision two distinct isomers of the alkyl-alkene complex, with either the primary or the secondary alkene carbon atom as the proximal Cp. This leads to the alternative primary and... [Pg.514]

Recently, however, examples of intramolecular triplet sensitization have been described. Alkyl aryl ketones with pendant azido groups in the alkyl moiety were irradiated into the benzoyl chromophore. The excited alkylphenyl ketones undergo intersystem crossing to their triplet states within picoseconds and they can then transfer their triplet energy to the nearby alkyl azido group. This process... [Pg.509]

PMA is a tough leathery resin with a low Tg and a solubility parameter of 10.5 H. In polymers of alkyl acrylates the solubility parameter decreases as the size of the alkyl group increases. The flexibility also increases with the size of the pendant groups but because of side chain crystallization this tendency is reversed when the alkyl group has more than ten carbon atoms. Polyalkyi acrylates are readily hydrolyzed by alkalis to produce salts of polyacrylic acid. The copolymer of ethyl acrylate (95%) and chloroethyl vinyl ether (5%) is a commercial oil-resistant elastomer. [Pg.158]

Alkyl-2-cyanoacrylates are readily polymerized in the presence of weak bases such as water. Because of the presence of the strong polar cyano pendant group these polymers (e.g. Super Glue) are excellent adhesives. Polybutyl-2-cyanoacrylate is tolerated by the body better than its lower alkyl homo-logues. Hence polybutyl-2-cyanoacrylate is used as an adhesive aid to stop bleeding in some surgical operations. [Pg.158]

An important advantage of the use of such added nucleophiles is that it allows controlled/living cationic polymerization of alkyl vinyl ethers to proceed at +50 to +70°C [101,103], relatively high temperatures at which conventional cationic polymerizations fail to produce polymers but result in ill-defined oligomers only, due to frequent chain transfer and other side reactions. Recently, initiators with functionalized pendant groups [137] and multifunctional initiators [ 138—140] have been developed for the living cationic polymerizations with added nucleophiles. [Pg.311]


See other pages where Alkylation pendant groups is mentioned: [Pg.1767]    [Pg.713]    [Pg.720]    [Pg.723]    [Pg.811]    [Pg.143]    [Pg.143]    [Pg.1332]    [Pg.303]    [Pg.68]    [Pg.27]    [Pg.266]    [Pg.1767]    [Pg.302]    [Pg.303]    [Pg.122]    [Pg.272]    [Pg.41]    [Pg.1767]    [Pg.713]    [Pg.720]    [Pg.723]    [Pg.811]    [Pg.143]    [Pg.143]    [Pg.1332]    [Pg.303]    [Pg.68]    [Pg.27]    [Pg.266]    [Pg.1767]    [Pg.302]    [Pg.303]    [Pg.122]    [Pg.272]    [Pg.41]    [Pg.519]    [Pg.238]    [Pg.541]    [Pg.446]    [Pg.41]    [Pg.187]    [Pg.610]    [Pg.286]    [Pg.74]    [Pg.498]    [Pg.75]    [Pg.639]    [Pg.85]    [Pg.19]    [Pg.262]    [Pg.133]    [Pg.519]    [Pg.238]    [Pg.19]    [Pg.65]    [Pg.386]   


SEARCH



Pendant group

© 2024 chempedia.info