Based on the Fourier transform IR spectroscopy together with the published NMR and X ray data, it was shown that cyclic co operative intramolecular hydrogen bond in calix[n]arene (n = 4, 6, 8) molecules is mainly responsible for their conformational state irrespective of the presence or absence of bulky substituents at the upper rim of the molecules. In accordance with the size of a macrocycle (n = 4, 6, 8), the stable conformation, secured by such a hydrogen bond, constitutes a cone, a pinched cone, and a pleated loop, respectively. The new, potentially competing system of hydrogen bonds in calix[6]arenes with 3 carboxymethyl 1 adamantyl substituents does not affect the conformational state of the macrocycle and its Н bonding. Six carboxy groups at the upper rim form in pairs three cyclic dimers, which does not disturb the hydrogen bonds of the hydroxy groups and the conformation of the macrocycle. In addition, the cavity of the molecule is considerably enlarged. The removal or rearrangement of the guest molecules in the solid calixarene by heating up to 180 °С only slightly affects the conforma tional state of macrocycles bearing bulky substituents, whereas in calixarenes devoid of such substituents, the similar procedure leads to somewhat of a distortion of the macrocycles (judging from the IR spectral indications of hydrogen bonding).
The effects of the concentration and functionalization of carbon nanotubes on the degree of conversion of epoxy groups in epoxy-amine compositions based on ED-20 epoxy oligomer and the PEPA curing agent are studied. It has been shown that increasing the concentration of functionalized carbon nanotubes (CNT) from 0 to 0.5 % increases the degree of conversion of the epoxy groups during curing at a room temperature. Further increase in concentration CNT of up to 1 % does not effect on the reaction kinetics. For native CNT not established such a relationship. Explains such a pronounced effect on the f-CNT aminolysis reaction kinetics and ultimate degree of conversion of epoxy groups, apparently, the catalytic effect of oxygen-containing groups (hydroxyl, carboxyl, and others) grafted to the surface of CNTs and their direct involvement in the reaction. By optical microscopy showed that the size of the agglomerates of nanotubes were substantially higher in the native systems than in the system with the functionalized nanotubes. These results may be important for the development of creation of epoxy composites modified by nanoparticles.
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