Grafting of poly-β-alanine onto carbon black: The hydrogen transfer polymerization of acrylamide catalyzed by n-butyllithium in the presence of carbon black

The hydrogen transfer polymerization of acrylamide (AAm) catalyzed by n-butyllithium in the presence of carbon black was carried out at 80–100°C and the grafting of poly-β-alanine (nylon 3) was investigated. It was suggested that the growing polymer anion was captured by the quinonic oxygen group on the surface of carbon black. Furthermore, the growing polymer anion reacted with the phenolic hydroxyl group on the surface to give ungrafted polymer and the lithium phenolate (O⁻Li⁺) group (chain transfer to phenolic hydroxyl group). The O⁻Li⁺ group formed was considered to be capable of initiating the hydrogen transfer polymerization of AAm. Accordingly, during the hydrogen transfer polymerization in the presence of carbon black, poly-β-alanine was effectively grafted by the termination of growing polymer anion and the propagation of the polymer from the O⁻Li⁺ group on the surface. The grafting ratio was determined to be 60–80%. The carbon black obtained from the polymerization gave a stable colloidal dispersion in water, N,N-dimethylformamide, and formic acid. Furthermore, it was found that the ratio of hydrogen transfer polymerization to normal vinyl polymerization (T ratio) increased with an increase in polymerization temperature.