Reactive carbon black having active phenyl ester groups: Preparation and reaction with functional polymers having hydroxyl or amino groups

Abstract

The introduction of active phenyl ester groups onto carbon black, such as p-nitrophenyl ester and pentachlorophenyl ester groups, was achieved by the reaction of carboxyl groups on the surface with the corresponding phenols by use of N,N′-dicyclohexylcarbodiimide as a coupling agent. The amounts of p-nitrophenyl ester and pentachlorophenyl ester groups introduced onto the surface were determined as being 0.26 mmol/g and 0.19 mmol/g, respectively. By the reaction of the carbon black thus obtained with commercially available polymers having hydroxyl or amino groups, the latter polymers were found to be grafted onto the surface via ester or amide bonds. For instance, by use of the reactive carbon black bearing p-nitrophenyl ester groups, the percentage of grafting of poly(propylene glycol) ( M n = 3.0 × 10 3 ), diol-type poly(dimethylsiloxane) (SDO; M n = 1.8 × 10 3 ), and diaminetype poly(dimethylsiloxane) ( M n = 3.0 × 10 3 ) was found to be as high as 25.0 %, 23.1 %, and 61.5%, respectively. The percentage of grafting increased with increase in the molecular weight of functional polymer, but the number of grafted polymer chains decreased. This is probably because the reactive groups become shielded by grafted polymer chains, and this effect increases with an increase in their molecular weight. The relationship between the number of grafted polymer chains (G n) and the molecular weight ( M n ) of SDO was found to be G n = 9.05 × 10 −2 M n −0.78 . The carbon black obtained from the reaction formed stable dispersions in good solvents for the grafted polymer.