Condensation oligomers

Fig. 8.14 TEM images showing (A) self-assembled layers of individual myoglobin molecules wrapped by condensed oligomers of AMP (B) top view of single sheet showing ordered superstructure of the hydrophobic organoclay wrapped myoglobin molecules.

Isocyanates can also be advanced into a variety of intermediate products that contain different forms of condensation oligomers. These advanced products are typically used in applications where the reactivity or the viscosity of the isocyanate is modified for specific requirements in an end-use application. 

Given the ineluctable fact that both side reactions are intrinsic to the very nature of the -2,5-Fu—CH2— unit formed in the initial FA self-condensation oligomers, no obvious way to avoid, or indeed minimize them, has yet been found. 

Ordinarily, silanes are applied to a substrate as monomeric, hydrolyzed species. The effectiveness of a silane is better when applied as monomeric silane rather than condensed oligomers. These silane films are very thin with a thickness on die order of several nanometers and, thus the strength of the film is rather insignificant in terms of the overall mechanical properties of a composite material. However, a sUane primer is applied as a rather concentrated, condensed species, forming a film of a few hundred nanometers. Thus, the mechanical properties of the film itself can contribute to the composite properties. For this type of silane primer as well as the structure of silane on a solid surface, consideration of a kinetic effect and a thermodynamic effect is very important. 

Figure 3.17. Models of [A) cyclic trisilicic. (B) cubic octasilicic acids, and (C) and ( )) the corresponding theoretical colloidal particles formed by condensing monomer to form closed rings until the original species is completely surrounded by one layer of deposited silica bearing silanol groups. When formed above pH 7 the inner silica contains few silanol groups. Different kinds of incompletely condensed oligomers could form the cores of colloidal particles. There is no evidence that A and B are specifically involved. Spheres, oxygen atoms black dots, hydrogen atoms. Silicon atoms are not visible. [From Her (97b) by permission of Plenum Press.]...

Figure 29 Variation of the lap-shear strength as a function of the test temperature between 25 and 450°C. Assemblies made by bonding (a) TU-2 titaninm alloy (b) ZIO CNT 1810 stainless steel with adhesive films prepared from condensation oligomers 31.

Such interactions only exist after the condensing oligomer has reached a certain size, with the cyclization being impossible when they are still too small. 

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