Effects of structural order

In the second part of this section we will discuss the effects of structural ordering on the transport for the case of diindenoperylene (DIP). As we have demonstrated in the former section, DIP has proven to be less susceptible to chemical degradation and, therefore, represents a prototypical organic semiconductor to study the relations between structure and electronic transport. 

WEINKAUF PAUL Effects of Structural Order on Barrier Properties... 

To discuss the effect of structural ordering of the polymer on selectivity, we have been focusing on secondary structures of poly(o -amino acid)s, i.e., polypeptides.They provide rigid and exact conformations, such as a-helix and 3-structure, spontaneously if polymerization is done with a purely chiral amino acid. The poly(L-alanine), poly(L-leucine), and poly(L-phenylalanine) with a terminal reactive trimethoxysilyl group can be prepared by the corresponding iV-carbox-yanhydrides and 3-aminopropyltrimethoxysilane as an initiator for polymerization. However, in this case, a... 

Weinkauf, D.H., and Paul, D.R., Effects of Structural Order on Barrier Properties, Chapter 3 in Barrier Polymers and Structures, W. J. Koros Ed., American Chemical Society (1990). 

As part of an independent study of catalytic asymmetric cyclopropanation, Denmark et al. described a systematic investigation of the effect of addition order, stoichiometry and catalyst structure on sulfonamide-catalyzed Simmons-Smith cyciopropanations. Although early studies had shown promising levels of enantios-electivity, higher selectivity would be required for this to be a synthetically useful transformation. The principal issues that were addressed by this study included ... 

The stability of a carbanion (or ion pair) is increased by certain substituents and decreased by others. It is possible to rank the various structures in an order of increasing stability of the carbanion just as was done for carbonium ions. It will be recalled that our information about carbonium ions does not suffice for a prediction of the effect of temperature changes on the relative stabilities, and that it is unknown to what degree an increase in stability actually reflects a decrease in potential energy. The situation is similar in the case of carbanions the precise relationship of the stabilities is an unknown function of the temperature. It is also likely that the effects of structural changes are somewhat dependent on the solvent. Nevertheless it is possible to make valuable qualitative comparisionsof the various structures and to interpret them in terms of resonance and other potential energy quantities. 

Koe, J. R. Fujiki, M. Nakashima, H. Motonaga, M. Helical Poly(diarylsilylene)s Effects of Higher Order Structure on Optical Activity. In Synthetic Macromolecules with Higher Order Structure, Khan, I. M., Ed. ACS Symposium Series 812 Washington DC, 2002 pp 67-86. 

The differences in the rates of decomposition of the various initiators are related to differences in the structures of the initiators and of the radicals produced. The effects of structure on initiator reactivity have been discussed elsewhere [Bamford, 1988 Eastmond, 1976a,b,c Sheppard, 1985, 1988]. For example, k,i is larger for acyl peroxides than for alkyl peroxides since the RCOO- radical is more stable than the RO radical and for R—N=N—R, kd increases in the order R = allyl, benzyl > tertiary > secondary > primary [Koenig, 1973]. 

Structure of Adsorbed Layers of Interacting Biopolymers — Effect of the Order of Addition to the Interface... 

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