Dispersion of submicron-sized SiO2/Al2O3-coated TiO2 particles and efficient encapsulation via the emulsion copolymerization of methacrylates using a thermoresponsive polymerizable nonionic surfactant

• Published in: Polymer journal Vol. 55; no. 5; pp. 617 - 629
• Main Authors: Hasan, Md. Kamrul, Enomoto, Kazushi, Kikuchi, Moriya, Narumi, Atsushi, Takahashi, Shigeki, Kawaguchi, Seigou
• Format: Journal Article
• Language: English
• Published: Tokyo Nature Publishing Group 01.05.2023
• Subjects: Aluminum oxide; Copolymerization; Emulsion polymerization; Encapsulation; Initiators; Maleic acid; Monomers; Polymethyl methacrylate; Rotation; Silicon dioxide; Sodium; Surfactants; Titanium; Titanium dioxide
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-023-00757-w

Submicron-sized SiO2/Al2O3(Si/Al)-coated titanium dioxide (Si/Al-TiO2) particles were encapsulated through the emulsion copolymerization of methacrylates using a thermoresponsive polymerizable nonionic surfactant, NE-10. An optimized water-dispersion method was developed to disperse Si/Al-TiO2 dried powders after various methods were investigated, such as using an ultrasonic homogenizer, a paint shaker, and a pot mill rotator (PMR) in the presence of partially neutralized poly(isobutylene-alt-maleic acid). The ultrasonic homogenizer successfully dispersed Si/Al-TiO2 in water, whereas the paint shaker and PMR caused overdispersion and broke the SiO2/Al2O3 shell. The optimal dispersion of Si/Al-TiO2 was obtained under the following conditions: 40 wt% solid content, 0.3 mm SiO2 beads, 0.25 wt% ISOBAM-600 (neutralization degree = 0.7), rotating speed <100 rpm, and rotating time <4 h. The encapsulation efficiency (Fen) was affected by the monomer and initiator types, NE-10 and sodium dodecyl sulfonate concentrations, and whether the process was batch or semibatch. The NE-10 concentration exhibited a significant effect on Fen; the optimal NE-10 addition was 1.4–2.5 mg for 1.0 g of Si/Al-TiO2. Fen > 90% was achieved using 0.25 g methyl methacrylate and 0.75 g n-butyl methacrylate, following a two-step semibatch emulsion copolymerization under optimized conditions. Compared to bare Si/Al-TiO2, the encapsulated hybrid particles showed a higher reflectance and dispersion stability in water.Submicron-sized SiO2/Al2O3(Si/Al)-coated titanium dioxide (Si/Al-TiO2) particles were encapsulated through the emulsion copolymerization of methacrylates using a thermoresponsive polymerizable nonionic surfactant, NE-10. An optimized water-dispersion method was developed to disperse Si/Al-TiO2 dried powders using an ultrasonic homogenizer, a paint shaker, and a pot mill rotator in the presence of partially neutralized poly(isobutylene-alt-maleic acid). The encapsulation efficiency (Fen) was affected by the monomer and initiator types, NE-10, and sodium dodecyl sulfonate concentrations. Fen > 90% was achieved by a two-step semibatch emulsion copolymerization under optimized conditions.