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Pendant groups, effect

Although it is generally accepted that the molecules should be long and rodshaped, it is also possible to introduce pendant groupings that will disrupt the packing of the molecules and hence extend the nematic range. Consider structures of the type (25) and (26)  [Pg.65]

The N I transition falls in proportion to the size of the substituent in going from X = F, Cl, Br, I, NO2, A change in the size of the pendant group [Pg.66]


M.R. Pixton, D.R. Paul, Gas transport properties of polyarylates part I connector and pendant group effects, J. Polym. Sci. Part B Polym. Phys. 33 (7) (1995) 1135-1149. [Pg.92]

In the methacrylate homologous series, the effect of side-chain bulkiness is just the opposite. In this case, however, the pendant groups are flexible and offer less of an obstacle to free rotation than the phenyl group in polystyrene. As chain bulk increases, molecules are wedged apart by these substituents, free volume increases, and Tg decreases. [Pg.255]

The hindered secondary amines can be highly effective photostabilizers for various polymers (]+.,5.,.6) Various hindered amines have been shown to retard oxidation, but most share the common feature of being secondary or tertiary amines with the a-carbons fully substituted. The most widely exploited representatives of this class are based on 2,2,6,6-tetramethylpiperidine either in the form of relatively simple low molecular weight compounds, or more recently as backbone or pendant groups on quite high molecular weight additives ( i.,5.,6). The more successful commercial hindered amines contain two or more piperidine groups per molecule. Photo-protection by tetra-methylpiperidines (near UV transparent) must result from the interruption of one or more of the reactions 1 to 3. Relatively recent results from our own laboratories, and in the open literature will be outlined in this context. [Pg.52]

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]

Hydrative cyclization of diynes with ruthenium catalyst has been reported for the synthesis of sulfolenes or enones in aqueous medium.381 Reactions of unsymmetrical 1,6-diynes have been investigated, and some substrates are found to exhibit a directing effect of the ketone moiety in a pendant group. [Pg.356]

Non-leaving ligand effects, for a series of 13-, 14- and 15-membered tetraaza-macrocycles with amine or carboxylate pendant groups, have... [Pg.80]

The tuning of electron injection and transport in PF has been undertaken by Shu s group [354], who introduced electron-deficient oxadiazole units as pendant groups in fluorene copolymer 257. The introduction of oxadiazole units into the PF can potentially improve the electron transport properties of the polymer, while their bulkiness can help to suppress aggregation effects (Chart 2.68). [Pg.150]

A reasonably large difference in diastereomeric excess was observed between product 47b with an adjacent methyl ester and 48b with a primary alcohol in the equivalent position [57]. It was noted by the authors that in cases involving a 1,3 system, changing the pendant group from a primary allylic alcohol to a methyl ester caused a reversal of facial selectivity [54, 58]. The same effect was absent in the 1,2 systems 51b and 52b studied. The diastereomeric ratio in the latter case was attributed mainly to catalyst control [58]. [Pg.50]

Due to the importance of polymer chemistry for the chemical industry, considerable effort has been devoted to the smdy of the effects of light on polymeric materials. The photochemistry of polymers is complex. However, it is well established that PFR occurs in some aromatic polyesters [211-222] and polyamides [223,224]. This process can take place either in the main chain of the polyester or in the pendant groups. [Pg.109]


See other pages where Pendant groups, effect is mentioned: [Pg.374]    [Pg.41]    [Pg.75]    [Pg.82]    [Pg.82]    [Pg.87]    [Pg.389]    [Pg.65]    [Pg.688]    [Pg.385]    [Pg.11]    [Pg.73]    [Pg.27]    [Pg.374]    [Pg.41]    [Pg.75]    [Pg.82]    [Pg.82]    [Pg.87]    [Pg.389]    [Pg.65]    [Pg.688]    [Pg.385]    [Pg.11]    [Pg.73]    [Pg.27]    [Pg.2603]    [Pg.519]    [Pg.238]    [Pg.95]    [Pg.170]    [Pg.504]    [Pg.541]    [Pg.138]    [Pg.446]    [Pg.23]    [Pg.548]    [Pg.182]    [Pg.105]    [Pg.113]    [Pg.114]    [Pg.284]    [Pg.610]    [Pg.184]    [Pg.51]    [Pg.106]    [Pg.188]    [Pg.463]    [Pg.51]    [Pg.35]   
See also in sourсe #XX -- [ Pg.75 , Pg.82 , Pg.87 ]




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Intramolecular Effects of Pendant Groups

Pendant group

Rigid pendant groups, effect

Transitions pendant group effects

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