The solvent-free chemical modification (SFM) of fullerene (C
60) by polyethylene glycol with amino terminal (amino-PEG) was studied in order to improve the fullerene dispersability. The effect of the stirring rate and the C
60 particle size on the modification yield was investigated in the temperature range 60-120°C for 3-24 h. As a result, 65 % of C
60 was modified at 60°C for 24 hr to disperse in ethanol. The effect of C
60 particle size on the yield was found to be more significant than that of the stirring rate. Therefore, the SFM is more sensitive to the collision frequency between C
60 and amino-PEG compared to the diffusion of C
60 in amino-PEG.
In order to understand the chemical modification mechanism, simulation was performed based on a shrinking-core model assuming a chemical reaction as a rate limiting step.Using this model it was possible to estimate the number of amino-PEG molecules attached to C
60. The results of simulation fit well the gel permeation chromatography (GPC) data collected in the early period of reaction considering that one amino-PEG attached to C
60. As for the final period of reaction, the number of attached amino-PEG molecules increases according to the GPC data but the simulation shows opposite tendency.This tendency was explained by decrease in C
60 surface activity and by the additional reaction between products in the fluid phase.
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