Antioxidant Activity of Methano- and Cyclopentenofullerenes

Kinetics and Catalysis - The rate constant of the reaction of methano- and cyclopentenofullerenes (С60R) with a peroxyl radical (PhCH(OO?)CH3) was measured in a model system of the...     

Reactions of fullerene C60 with methyl methacrylate radicals: A density functional theory study

We have investigated the stepwise addition of four growing methyl methacrylate (MMA) radicals to C₆₀ fullerene, taking into account all possible types of the formed adducts. This reaction set is a reliable approximation for understanding the MMA polymerization process in the presence of C₆₀ fullerene. We have analyzed the structures of the fullerene-MMA adducts and energy parameters of their formation (heat effects and activation enthalpies). We found that up to three MMA growing radicals are favorably attached to C₆₀ as the fullerene-MMA trisadduct is a stable radical of the allyl type. It is inactive for further radical addition, and the elimination of the hydrogen atom from the growing MMA radical becomes preferable. The effects of steric factors and structures of the products of multiple growing MMA radical additions to C₆₀ on the radical polymerization of MMA in the presence of C₆₀ fullerene are considered.     

Simulation of Potentially Possible Reactions at the Initial Stages of Free-Radical Polymerization of Styrene and Methyl Methacrylate in the Presence of Fullerene C<Superscript>60</Superscript>

The quantum-chemical simulation of possible reactions occurring at the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C⁶⁰ is performed. The reactions of interaction between initiating and model short-chain growing radicals containing from one to three monomer units with fullerene are considered. It is shown that, at the initial stage of styrene polymerization, the addition of short-chain growing radicals to fullerene predominates (with respect to the reaction of chain propagation). In the case of methyl methacrylate polymerization in the presence of fullerene C⁶⁰, the induction period is absent because of a higher probability of the initiation and chain propagation reactions (compared with the chain-termination reaction of short growing poly(methyl methacrylate) chains on fullerene C⁶⁰). The formation of bis- and trisadducts of fullerene C⁶⁰ with short-chain styrene and methyl methacrylate growing radicals is analyzed. The quantum-chemical simulation results are confirmed by electron spectroscopy and ESR studies.     

On the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C<Subscript>60</Subscript>

It has been demonstrated experimentally and theoretically that the essentially different inhibiting effects of fullerene C₆₀ on the initial stage of the polymerizations of styrene and methyl methacrylate (including complete hampering of styrene polymerization throughout a long induction period) are of common kinetic nature. The difference arises from the competition between C₆₀ and the monomer not for initiating radicals but for radicals originating from the monomer; that is, the difference stems from the competition between the chain propagation reactions and the termination reactions on fullerene molecules. As a consequence, the further development of the process is determined by the relative reactivities of the radicals toward C₆₀ and towards their parent monomers.     

Quantum chemical modeling of the addition reactions of 1‐n‐phenylpropyl radicals to C60 fullerene

Modeling of the addition of various radicals to C₆₀ fullerene is currently an active research area. However, the radicals considered are not able to adequately model polymeric radicals. In this work, we have performed a theoretical study of the possible reactions of C₆₀ fullerene with 1‐n‐phenylpropyl radicals, which are used to model polystyrene radicals. Several possible ways of subsequent addition of up to four 1‐phenylpropyl radicals to C₆₀ have been analyzed, the structures of the intermediates have been defined and thermal properties, such as the activation enthalpies of the corresponding reactions, have been calculated using density functional theory with the approximation of PBE/3z. It is shown that the topology of the spin density distribution on the fullerenyl radical causes regioselectivity for further radical addition. According to the energetic characteristics of the reactions, we assume the possibility of formation of products of one‐, two‐, three‐, and four‐ addition of the growth radical to the fullerene core in radical polymerization of styrene in the presence of C₆₀ fullerene. © 2016 Wiley Periodicals, Inc.