In order to improve the dispersibility of carbon black (CB) in organic solvent, the grafting of poly(L-lactic acid) (PLLA) onto CB surface by (1) polycondensation of L-lactic acid (LLA) in the presence of CB and (2) grafting by the reaction of PLLA with CB surface in the presence of catalyst was investigated. It was found that, during the polycondensation of LLA in the presence of CB, the grafting of PLLA onto CB surface proceeded both in the absence and in the presence of scandium (III) triflate (Sc(OTf)3) as catalyst to give PLLAgrafted CB (1), but the percentage of PLLA grafting onto CB in the presence of Sc(OTf)3 was higher than that in the absence of Sc(OTf)3. In addition, the condensation reaction of surface functional groups on CB with PLLA was successfully achieved in the presence of Sc(OTf)3 to give PLLA-grafted CB (2). The average particle size of CB considerably decreased by grafting of PLLA onto the surface. Therefore, it was concluded that the aggregation of CB particles was considerably destroyed and prevented by grafting of PLLA onto the surface. The PLLA-grafted CBs gave a stable dispersion in polar solvents, such as DMSO and 1,4-dioxane, which are good solvents for PLLA.
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