Ozonolysis of polydienes

Abstract

Boehmite (AlOOH) nanoparticles have been synthesized in subcritical (300 bar, 350 °C) and supercritical (300 bar, 400 °C) water. The formation and growth of AlOOH nanoparticles were studied in situ by small‐ and wide‐angle X‐ray scattering (SAXS and WAXS) using 80 keV synchrotron radiation. The SAXS/WAXS data were measured simultaneously with a time resolution greater than 10 s and revealed the initial nucleation of amorphous particles takes place within 10 s with subsequent crystallization after 30 s. No diffraction signals were observed from Al(OH)3 within the time resolution of the experiment, which shows that the dehydration step of the reaction is fast and the hydrolysis step rate‐determining. The sizes of the crystalline particles were determined as a function of time. The overall size evolution patterns are similar in sub‐ and supercritical water, but the growth is faster and the final particle size larger under supercritical conditions. After approximately 5 min, the rate of particle growth decreases in both sub‐ and supercritical water. Heating of the boehmite nanoparticle suspension allowed an in situ X‐ray investigation of the phase transformation of boehmite to aluminium oxide. Under the wet conditions used in this work, the transition starts at 530 °C and gives a two‐phase product of hydrated and non‐hydrated aluminium oxide.

Synthesis and Ozone Degradation of Alternating Copolymers ofN‐Substituted Maleimides with Diene Monomers

“…Judging from the results obtained in this study, the methyl substitution decreased their ozone degradation rate. This seemed to be contradictory to the fact of polyisoprene degradation faster than polybutadiene reported in the literature . Steric factor may more significantly affect the degradation rate rather than polar factor for the ozone degradation of DMPD copolymers in the present study.…”

“…This seemed to be contradictory to the fact of polyisoprene degradation faster than polybutadiene reported in the literature. [27][28][29] Steric factor may more significantly affect the degradation rate rather than polar factor for the ozone degradation of DMPD copolymers in the present study. The repeating units of the electron-accepting monomers also affected their degradation rates.…”

Ozone and its Reactions with Diene Rubbers

“…It is also known that some reactions of the polymers proceed more slowly, compared with their low molecular analogues (catalytic hydrogenation). The folded or unfolded forms of the macromolecules provide various conditions for contact of the reagents with the reacting parts [4,25]. By using the modified version of this principle [26] it was possible to explain the proceeding of reactions without any specific interactions between the adjacent C=C bonds and the absence of diffusion limitations.…”

Effect of cis / trans isomerism on selective oxidation of olefins with nitrous oxide

“…[5a] In turn, the F cleav value for trans-3-heptene agrees quite well with F cleav ≈ 15% for ketonization of C=C bonds of nitrile-butadiene rubber, [5b] which contains predominantly trans-1,4-butadiene units. 9 Based on the obtained results one can suggest that, similar to cycloaddition of other 1,3-dipoles to C=C bond, the N 2 O reaction with olefins proceeds stereospecifically. If this is the case, geometrical isomerism of olefin will determine the structure of 1,2,3-oxadiazole intermediate.…”