The story of the “self-healing” materials was developed by the research teams in University of Illinois at Urbana-Champaign. My advisor, Dr.Kessler was beginning his Ph.D. research in the one of these teams. This novel concept is publised on Nature, Feb 15, 2001, to describe a material with the ability to heal itself autonomically, i.e. a self-healing material.

One simple approach of “self-healing” materials is a microencapsulated system. In a structural composite matrix, catalyst capable of triggering the polymerization of the healing agent and microcapsules containing healing agent are embedded. Once damage occurs, the cracks ruputure the microcapsules, releasing the healing agent, which contacts the catalyst to form polymers that bonds the crack faces together.

the nanoparticles response to different solvents!

How?
An asymmmetric difunctional initiator, “Y-silane” is designed and synthesized. “Y-silane” combines the initiators for both ATRP and NMRP together, as well as a silane group which can immobilize the “Y” difunctional initiator on the surface of silica nanoparticles.

Once the Y-initiator-terminated self-assembled monolayer (Y-SAM) forms on the nanoparticle surface, two different types of polymerization are initiated from the surface: ATRP of tert-butyl acrylate (PtBA), and then, NMRP of styrene at higher temperature. Finally, subsequent hydrolysis of PtBA produces amphiphilic mixed poly (acrylic acid) (PAA)/PS brushes.

These “hairy” nanoparticles response to environmental changes, such as in chloroform, the selective solvent for PS, or in methanol, a selective solvent for PAA.

These results were published on JACS, 2005.