Janus particles stabilized alkenyl succinic anhydride emulsion as internal sizing agent

Alkenyl succinic anhydride (ASA) is widely used in papermaking industry as an internal sizing agent. In situ emulsification of ASA using cationic starch is conventionally practiced because of the low shelf life of ASA emulsion. We synthesized Janus particles by surfactant-free seeded polymerization to stabilize ASA emulsion. The morphology evolution and anisotropic compositions of Janus particles were confirmed by transmission electron microscopy. The Janus particles showed a strong tendency to adsorb at the ASA–water interface and enhanced the stability of ASA emulsion. The droplet size of ASA emulsion decreased and emulsion phase volume increased with the concentration of Janus particles increased. In comparison with cationic starch, Janus particles exhibited superior emulsification performance in ASA emulsion. The ASA emulsion stabilized by Janus particles was used as an internal sizing agent for cellulose paper. The results of sizing degree and Cobb30 showed that the sizing performance of ASA emulsion stabilized by Janus particles was significantly improved. Our study provides a better choice of preparing ASA emulsion for paper sizing and promotes the application of Janus materials in paper industry. Graphical abstract