A Simple Preparation of C60-Poly(ethylene glycol) Gel and its Properties

Abstract

Poly(ethylene glycol) (PEG) biradicals formed by thermal decomposition of macroazo-initiator, (Azo-PEG)n, which were prepared by the polycondensation of 4,4′-azobis(4-cyanopentanoyl chloride) with PEG, were successfully trapped by C60 fullerene to give C60-PEG gel containing C60 fullerene at cross-linked point. It was found that when the feed ratio (PEG/C60) was less than 3, PEG-grafted C60 fullerene was formed, but the gelation does not proceed. On the contrary, when the feed ratio exceeded 4, the gelation of PEG successfully proceeded. In the case of the feed ratio is 4, the gel fraction was about 80%, and it was gradually decreased with an increase in the feed ratio. The gel fraction increased with increasing reaction temperature and reached to 80% at 80 °C. It is concluded that the reaction conditions to give highest gel fraction is summarized as follows: the feed molar ratio, 5 (mol/mol); concentration of C60, 3.5 mmol/L; 70 °C; 24 h. The thermal stability of C60-PEG gel was dramatically increased in comparison with that of (Azo-PEG)n. C60-PEG gel was swelled in solvents, such as water, methanol, and THF and degree of swelling was about 5.1 to 7.8. Breaking strength decreased with increasing the feed molar ratio.