Shell-crosslinked polymeric capsules

A new variation of interfacial polymerization was developed by Russell and Emrick in which functionalized nanoparticles or premade oligomers self-assemble at the interface of droplets, stabilizing them against coalescence. The functional groups are then crosslinked, forming permanent capsule shells around the droplets to make water-in-oil (Lin et al. 2003 Skaff et al. 2005) and oil-in-water (Breitenkamp and Emrick 2003 Glogowski et al. 2007) microcapsules with elastic membranes. 

The amine-based Henry reaction catalyst was encapsulated via the interfacial polymerization of oil-in-oil emulsions. PEI was encapsulated by dispersing a methanolic PEI solution into a continuous cyclohexane phase. Upon emulsification, 2,4-tolylene diisocyanate (TDI) was added to initiate crosslinking at the emulsion interface, forming polyurea shells that contain free chains of PEI. The microcapsules crenate when dry and swell when placed in solvents such as methanol and dimethylformamide, suggesting a hollow capsule rather than a solid sphere formation. The catalyst loading was determined to be 1.6 mmol g . ... 

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