Saturday, August 4, 2012

Mechanistic investigation and selectivity of the grafting onto C60 of macroradicals prepared by cobalt-mediated radical polymerization

 The grafting mechanism of poly(vinyl acetate) macroradicals prepared by cobalt-mediated radical polymerization (CMRP) onto C60 is investigated. Experimental conditions such as the polymerization mechanism, the temperature and the stoichiometry directly impact the grafting mechanism and the nature and stability of the final products.
Mixtures of PVAc/C60 adducts having between one and eight polymer chains per C60 are formed. C60 has a well-known radical scavenging ability.

PVAc/C60 adducts prepared with low [PVAc]:[C60] ratios may contain weak C60-C60 bonds that further dissociate and account for the instability of the products. The formation of such dimers can be lessened by increasing the temperature from 30°C to 100°C. The temperature increase also allows a complete dissociation of the PVAc-Co dormant species into PVAc° macroradicals and an almost quantitative grafting of eight PVAc chains onto C60, leading to well-defined C60(PVAc)8 octa-adducts.
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