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Alumina particle surface interaction in copolymer of isobutylene and maleic anhydride aqueous solution characterized by colloidal probe atomic force microscopy

Yamamoto, Masahiro, Shimai, Shunzo, Oguma, Kazuki, Wang, Shiwei, Kamiya, Hidehiro
Powder technology 2019 v.354 pp. 369-376
aluminum oxide, aqueous solutions, atomic force microscopy, composite polymers, dispersants, gelation, maleic anhydrides, powders, silica
By the addition of isobutylene-maleic anhydride copolymer, Al₂O₃ aqueous suspensions retain fluidity for approximately 1 h and then gelation occurs. The bi-functionality mechanism as dispersant and gelling-agent of the copolymer was investigated by colloidal probe atomic force microscopy. The time-dependent surface interaction between Al₂O₃ particles and sapphire substrates were compared to those of SiO₂, the suspension of which did not appear experience gelation. After 40 min, repulsive forces increased slightly and attractive forces decreased dramatically with short-range character, corresponding to the dispersant action of the copolymer in aqueous Al₂O₃. As aging time increased to 2 h, a large repulsive force and long-range attractive force developed. With the aging time going to 3 h, the repulsive force disappeared and only long-range attractive forces remained. On the contrary, in the case of SiO₂, long-range repulsive force was only observed after the addition of ISOBAM, and long-range attractive interactions were not observed with increased of aging time. However, no time-dependent long-range attractive interaction was observed in the SiO₂ suspension. Therefore, it seems gelation of the Al₂O₃ aqueous suspension was correlated to the long-range attractive interaction between Al₂O₃ surfaces.