title: Robust composite-shell microcapsules via pickering emulsification.
abstract: Microencapsulation technology has been increasingly applied toward the development of self-healing paints. Added to paint as a dry powder prior to spraying, the microcapsules store a liquid that can repair the protective barrier layer if released into a scratch. However, self-healing will not occur unless the microcapsules can withstand spray-painting, aggressive solvents in the paint, and long-term exposure to the elements. We have therefore developed a one-pot synthesis for the production of Pickering microcapsules with outstanding strength, solvent resistance, and barrier properties. Octadecyltrimethoxysilane-filled (OTS) microcapsules form via standard interfacial polycondensation, except that silica nanopowder (10-20 nm diameter) replaces the conventional surfactant or hydrocolloid emulsifier. Isophorone diisocyanate (IPDI) in the OTS core reacts with diethylenetriamine, polyethylenimine, and water to form a hard polymer shell along the interface. Compared to pure polyurea, the silica-polyurea composite improves the shelf life of the OTS by 10 times. The addition of SiO2 prevents leaching of OTS into xylenes and hexanes for up to 80 days, and the resulting microcapsules survive nebulization through a spray gun at 620 kPa in a 500 cSt fluid.
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Marcia W
authors: MW
authors: Patchan
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Benedict W
authors: BW
authors: Fuller
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Lance M
authors: LM
authors: Baird
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Paul K
authors: PK
authors: Gong
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Erich C
authors: EC
authors: Walter
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Brendan J
authors: BJ
authors: Vidmar
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Ike
authors: I
authors: Kyei
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Zhiyong
authors: Z
authors: Xia
authors: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States.
authors: Jason J
authors: JJ
authors: Benkoski
keywords: hydrolysis; interfacial polymerization; microencapsulation; pickering emulsion; solvent resistance