Carbon Black Dispersing Agents based on Fully Hydrophilic Poly(N-Vinylamide): Surface Adsorption via Selective Interactions

Interface-stabilizing polymers are frequently used in commercial applications to provide long-lasting dispersions of colloids in liquid media. Although conventional poly(meth-)acrylate-based dispersing agents can easily be used in organic solvents, there is a strong need to develop environmentally benign water-based alternatives. Here, we present a novel, fully hydrophilic dispersing agent system for carbon black (CB) pigments based on partially hydrolyzed poly(N-vinylamides). The polymers can participate in hydrogen bonding, ion-dipole interactions and can be partially positively charged to engage in ion pair formation, providing strong surface affinity. Adsorption onto CB will occur through specific interactions between the polymer and surface-bound moieties, rather than the hydrophobic effect. Dispersants were synthesized using free radical copolymerization of N-vinylform- and acetamide, acidic hydrolysis and subsequent PEGylation. Full water solubility of the synthesized polymers was confirmed using fluorescence spectroscopy. Highly concentrated CB dispersions were prepared in acidic, neutral and basic media, which we identified to strongly affect the interactions between polymer and CB. The stability of CB dispersions was analyzed using ultracentrifugation and thermogravimetric analysis. The presented polymers were able to provide significantly more stable dispersions than a commercial reference product, showcasing the suitability of poly(N-vinylamines) as potent CB dispersing agents.