Oligomeric character

By eliminating the volatile components under vacuum, the reaction mixture yields oleous products which have been subjected to elemental and physico-chemical analyses (Table 26). The viscous oil products show an oligomeric character and a structure originating from the alternating copolymerization of an 02 molecule with the conjugated diene system. In fact, the absorption bands of the dienic systems are... 

The constitutional graphs of common compounds and those of Mobius compounds and knots (recently synthesized) are connected. The graphs of catenanes and rotaxanes, however consist of two or more components reflecting the dimeric (oligomeric) character of these compounds. 

A trimer (2,5-di(2-thienyl)pyrrole) containing pyrrole between two thiophene rings (78) [331] forms materials with conductivities up to 0.1 S cm". This low value is attributable to the oligomeric character of the soluble materials. The dimer pyrrole-thiophene (79) [332] has also been electropolymerized to materials conducting in the range 0.1—3 S cm and with a bandgap of 2.8 eV (440 nm) intermediate between polypyrrole and polythiophene. Bithiophene and dipyrrole fused with a... 

Lastly, a general comment about our employment of the term "polymer is in Older. Unfortunately, we have, to this point, been unsuccessful in determining the molecular weights of these reaction products. From the observations of l ing infusible, poorly soluble, and amorphous (by XRPD) we concluded that these materials were of at least oligomeric character. 

The acidic character of 5A zeolite as a function of the calcium content has been explored by different techniques propylene adsorption experiments, ammonia thermodesorption followed by microgravimetry and FTIR spectroscopy. Propylene is chemisorbed and slowly transformed in carbonaceous compounds (coke) which remain trapped inside the zeolite pores. The coke quantities increase with the Ca2+ content. Olefin transformation results from an oligomerization catalytic process involving acidic adsorption sites. Ammonia thermodesorption studies as well as FTIR experiments have revealed the presence of acidic sites able to protonate NH3 molecules. This site number is also correlated to the Ca2+ ion content. As it has been observed for FAU zeolite exchanged with di- or trivalent metal cations, these sites are probably CaOH+ species whose vas(OH) mode have a spectral signature around 3567 cm"1. 

Polymerization reactions of olefins and dienes cannot be treated here in detail. Knowledge of the early steps which occur on nickel, as in oligomerization reactions, help explain the course of polymerization reactions and particularly their stereospecific character, as in Ziegler-Natta polymerization. 

The difference in the effect of various endo-D-galacturonanases on oligomeric substrates [in particular, the difference in the rate of degradation of tri(D-galactosiduronic acid) and in the action pattern toward the tetrasaccharide] indicates, however, that it is not the substrate, but rather, the properties of the enzyme (in particular, the character of its active center) that constitute the determining factor. 

The subsequent import mechanism has not been clarified, but it has a remarkable character it can pass proteins in a folded or even oligomerized state. 

Multihydroxyl containing monomeric or oligomeric p-cyclodextrins (PCD) such as those attained by grafting with glycidyl ethers of protected polyols (glycerol and pentitols) appeared rather promising components for their amphiphilic character, connected to the presence of an hydrophobic pocket and an external hydrophilic shell with an amplified number of hydroxyl groups. 

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