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Self-healing materials

Dr. Leonid Ionov
Nikolay Puretskiy

We are interested in design of materials with self-healing surface properties using colloidal particles.

Self-healing switchable surfaces

It was found that hydrophilic silica particles almost completely immerse in wax after annealing in dry environment above wax melting point. On the other hand, the degree of particles immersion in wax decreases after annealing in aqueous environment. The surface properties of the particle-wax films are, therefore, switched between hydrophobic and hydrophilic states after annealing in air and in water, respectively. The hydrophilicity/hydrophibicity can be frozen by the cooling below the wax melting point. We also demonstrated possibility to produce hydrophilic/hydrophobic pattern on wax-particle films using local heating.

 

Scheme of switching of wax-particle surfaces. The hydrophilic particles are mixed with wax. Annealing in water and in air changes depth of immersion of the particles in oil layer that switches properties of the layer between hydrophilic and hydrophobic states.

Self-healing superhydrophobic surfaces

We developed the approach for synthesis of mechanically and solvent resistant raspberry-like particles.  The particles were prepared by immobilization of silica nanoparticles on the surface of silica microparticles coated by poly(glycidyl methacrylate) brush layer. The raspberry-like particles retain their structure after ultrasonication and exposure to organic solvents that allows their use as substrates for immobilization on polymers. Fabrication ultrahydrophobic surfaces using raspberry-like particles with immobilized poly(pentafluorostyrene) was also demonstrated.

 

Scanning electron microscopy of raspberry-like particles with poly(pentafluorostyrene) shell (a); Snap shots of water droplet standing on the film of raspberry-like particles (b) and water droplet upon water receding (c). 

We also developed an approach for the design of materials with self-repairable ultrahydrophobic properties. The materials are based on highly fluorinated crystalline fusible wax with incorporated colloidal particles. Due to the highly pronounced tendency of the wax to crystallize, the formation of the blends with rough fractal surfaces was observed. In order to prove their self-repairing ability, we mechanically damaged them by scratching, which removed most of the particles from the surface. Melting of the damaged blend resulted in the reorganization of the particles at the wax-air interface, restoring the initial structure and thus the ultrahydrophobic behavior. 

Schematic of materials with self-repairing ultrahydrophobicity. The ultrahydrophobic surface is formed from perfluorinated wax with colloidal particles. (a,b). Particles may be removed from the topmost layer by mechanical damage (c). Melting of the wax results in reorganization of the particles and their migration to the surface and restoration of the ultrahydrophobic behavior (a).

References

Ionov, L.; Synytska, A.
Self-healing superhydrophobic materials more
Physical Chemistry Chemical Physics 14 (2012), 10497-10502.

Puretskiy, N.; Stoychev, G.; Synytska, A.; Ionov, L.
Surfaces with self-repairable ultrahydrophobicity based on self-organizing freely-floating colloidal particles more
Langmuir 28 (8) (2012), 3679–3682.

Puretskiy, N.;  Ionov, L.
Synthesis of robust raspberry-like particles using polymer brushes more
Langmuir 27(6) (2011) 3006-3011

Puretskiy, N.; Stoychev, G.; Stamm, M.; Ionov, L.
Switchable surfaces based on freely floating colloidal particles more
ACS Applied Materials & Interfaces 6 (10) (2010) 2944-2948.

 
Self-healing materials
Self-healing materials

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