Thermal stability of the fullerene‐chain link in 6‐arm PS stars with a C₆₀ core

Abstract

The thermal stability of well‐defined hexa‐adducts (PS)6C60 in solution at temperatures around 100 °C has been studied by multi‐detector Size Exclusion Chromatography. The degradation reaction corresponds to a quantitative release of the polystyrene arms from the fullerene core through thermal cleavage of the PS‐C60 link. From the kinetics of formation of cut arms and the progressive decrease of the stars' functionality, we could establish that the reaction follows a stepwise “breaking” mechanism where a 6‐arm star is first converted to a 5‐arm star, then to a 4‐arm star, and so on down to the ungrafted arm. Furthermore, not only does the thermal stability of the PSC60 bond increase if the functionality of the star decreases, but the difference is large enough to allow determination of the kinetics constants for the first three steps. The activation energy for the breaking of an arm‐C60 link is about 65 kJ/mol. The stability of (PS)6C60 slightly decreases with an increase of the arm length. MALDI‐TOF mass spectroscopy has shown that both CC bonds in α and β positions to C60 can be cut, but the breaking of the direct fullerene‐arm bond is favored. We have also found that a polyisopreneC60 bond is about seven times less stable than a PS‐fullerene link upon heating. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4820–4829, 2004

Contemporary Mass Spectrometry and the Analysis of Synthetic Polymers: Trends, Techniques and Untapped Potential

“…By using ESI‐ion trap and ESI‐Q‐TOF instruments to monitor the changes in the observed end‐group distributions for samples held in an ambient atmosphere at 95 °C over differing periods of time, these authors proposed that the chains under investigation degrade via an epoxidation of terminal vinyl bonds followed by subsequent elimination of formaldehyde and 2‐oxopropionic acid methyl ester. The features of the apparent MWDs for the different end‐group functionalities detected in degraded polymer samples can also allow insights to be made into degradation mechanisms, as was demonstrated in a MALDI‐TOF study conducted by Audouin et al134 This study focussed upon the degradation of six‐armed poly(styrene) stars with fullerene cores held at around 100 °C in toluene. It was proposed that degradation proceeds via the rupture of CC bonds in the α and β positions to the fullerene, with two series of peaks corresponding to ruptures at these two sites being observed at a relative abundance ratio of around 3:1.…”

Revisit of polystyrene-modified fullerene core stars: A computational study

“…However, very recent experiments by temperature gradient interaction chromatography (TGIC) [8][9][10][11][12][13][14] observed the C 60 core stars with greater than six arms [15]. Although there have been plentiful studies on the arm-grafted C 60 fullerene both experimentally and theoretically [3][4][5][6][7][8][15][16][17], several questions still remain: why 6-arm-grafted C 60 core star is observed in every experiments with the most abundance; why greater than 6-arm-grafted C 60 core star is only observed by the latest experiments; how the arms are grafted on C 60 fullerene. In this work, we aim to systematically study the relationships between the grafted arms and C 60 fullerene by DFT calculations.…”

Oligo- and poly(fullerene)s for photovoltaic applications: Modeled electronic behaviors and synthesis

“…Prior work has shown that polymers can be grafted onto C 60 using atom transfer radical additions with Br‐terminated polymer chains . It is possible to control the points of addition of the polymers to just one phenyl ring on the fullerene sphere due to a mechanism of bromine transfer between radical states .…”