Nanoparticles bearing a photoreactive shell: Interactions with polymer matrice and polymer surface

 
In this presentation strategies for the attachment of photoreactive moieties onto the surface of silica nanoparticles, and potential applications of UV-reactive nanoparticles are discussed. Photosensitive nanoparticles bearing azidophenyl units at their surface were prepared from amino functionalized silica nanoparticles with 4-azidophenyl isothiocyanate. Under UV irradiation, nitrene groups are formed at the surface and the nanoparticles react with their environment (e.g. matrix polymers). Azidophenyl modified nanoparticles have been investigated as photo-crosslinking agents for C=C unsaturated polymers (polyisoprene and a derivative of polynorbornene). Here, photofunctional nanoparticles are used as non-migrating photoinitiators. In another approach, the UV induced immobilization of azidophenyl functionalized nanoparticles on inert polymer surfaces (e.g. polyethylene foils, polyester and polyamide fibres) has been demonstrated. Under appropriate conditions, dense nanoparticle layers are covalently attached to the polymer surfaces. The use of photoreactive nanoparticles opens new fields of application because they can be coupled to virtually any polymer surface, without the necessity to carry out a pre-treatment or coating of the targeted polymer substrate. Therefore, these particles my be termed "piranha" nanoparticles. In addition, the patterned attachment of nanoparticles onto the surface of photoreactive polymers is described. These approaches rely on the UV assisted generation of anchoring groups at the polymer surface which are capable of reacting with nanoparticles (e.g. amino-functionalized silica NP). Potential applications are discussed as well.