Grafting reaction of surface carboxyl groups on carbon black with polymers having terminal hydroxyl or amino groups using N,N′-dicyclohexylcarbodiimide as a condensing agent

Abstract

The grafting of polymers onto carbon black surface by the direct condensation of surface carboxyl groups with functional polymers in the presence of condensing agent was investigated. It was found that the grafting reaction of surface carboxyl groups with functional polymers having hydroxyl or amino groups readily proceeded in the presence of N, N′-dicyclohexylcarbodiimide (DCC) as a condensing agent at 30°C and the corresponding polymers were grafted onto carbon black surface with ester or amide bonds: the percentage of grafting of diol-type poly(propylene oxide) (PPG: Mn = 2.0 × 10 3) and diamine-type poly(dimethylsiloxane) (SDA: Mn = 1.7 × 10 3) was determined to be 24.5 and 40.2%, respectively. No grafting reaction onto carbon black surface, however, was observed in the absence of DCC. The percentage of grafting increased with increasing carboxyl group content of carbon black and increasing reaction temperature. The percentage of grafting and the number of grafted polymer chains decreased with increasing molecular weight of functional polymers, because the reaction of surface carboxyl groups was inhibited by the already grafted polymer chains. Polymer-grafted carbon black gave a stable colloidal dispersion in a good solvent for the grafted polymer.