Anti-Radical Activity of Fullerenes and Carbon Nanotubes in Reactions of Radical Polymerization and Polymer Thermal/Thermo-Oxidative Degradation

Abstract

The behaviour of fullerenes (mostly the C60 and C70) in a radical polymerization and during thermal/thermo-oxidative degradation of polymers is considered. The analysis of literature material clearly shows that fullerenes preferably act as scavengers of carbon-centered free radicals, and therefore they appear to be inhibitors for the radical polymerization and stabilizers for polymer materials.No distinct indication of any proved active or specific role for oxygen-centered radicals has been specified.As carbon nanotubes (CNTs) have electron affinities similar to those of fullerenes, and might therefore also be predicted to behave as radical traps in chain reactions such as polymerization and thermal degradation of polymers as well.

Radical scavenging efficiency of different fullerenes C60–C70 and fullerene soot

“…The apparent stabilizing role of fullerenes during thermooxidative degradation of polymers was confirmed by a recent set of investigations [32,33]. The stabilizing activity of fullerenes C 60 , C 60 / C 70 and C 70 , has been shown to be comparable to the activity of well-known hindered phenolic stabilizers, by means of model reactions of cumene and styrene initiated oxidation as well as in accelerated tests of polystyrene (PS) and polydimethylsiloxane (PDMS) rubber with fullerene moieties [34,35].…”

“…The analysis of the literature clearly shows that fullerenes preferably act as scavengers of carbon-centred free radicals, and therefore they appear to be inhibitors for the radical polymerization and thermal stabilizers for polymers. No distinct indication of any proved active or specific role for oxygencentred radicals has been identified [32]. The low rate constant for trapping of peroxy radicals by C 60 is k inh ¼ (3.1AE 1.1) Â 10 2 M À1 s À1 obtained in [59] and the inertness of peroxy radicals towards fullerene C 60 established by the chemiluminescence [60] indicates that fullerene C 60 is an extremely weak acceptor of peroxy radicals.…”

Biomedical potential of the reactive oxygen species generation and quenching by fullerenes (C60)

“…It is more likely that the observed effect involved physical quenching due to energy transfer, in which singlet oxygen was deactivated by conversion of its electronic excitation energy into vibration of O 2 and C 60 . Apart from this weak quenching of singlet oxygen, no study thus far, at least to our knowledge and according to the recent report [17], has demonstrated a significant scavenging capacity of pure, underivatized C 60 towards major oxygen-centered radicals. It is therefore plausible to consider the hypothesis that the ROS-deactivating capacity of various fullerene preparations might not be entirely related to the fullerene core itself, but also to the attached functional groups or various modifying agents introduced to provide water solubility.…”

“…This might appear somewhat surprising, having in mind the fairly low 1 O 2 -quenching capacity of pristine C 60 [6] and the lack of any documented ability for deactivation of other oxygencentered radicals [17]. While this suggests that covalently attached groups might play an important role in the ROS scavenging by derivatized C 60 , the dependence of ROS-deactivating capacity of fullerenes on the extent and/or type of functionalization has scarcely been directly assessed.…”

Antioxidant capacity of novel amine derivatives of buckminsterfullerene: Determination of inhibition rate constants in a model oxidation system

“…Underivatised fullerenes C 60 and C 70 are now widely known as effective scavengers of carbon-centred radicals [1][2][3][4][5][6][7][8][9][10]. They are recommended in practical end-use applications as inhibitors of chain radical polymerization and thermal stabilizers for polymers [2,5,6,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”