Nanocatalytic coatings

For industrial catalytic applications permanent immobilization of nanoparticles in carrier systems or on solid supports is extremely desired, since this eases manipulation and ensures purification of products, recycling of the precious catalyst and minimization of waste treatment. The high number of functional groups and the open structure of polymer brushes ensure stabilization and easy diffusion of reactants to the nanoparticle surface at the same time. These properties render polymer brushes as optimal canditates for the creation of nanocatalytic coatings.

Nanoparticles can be immobilized in such polymer brush layers either by covalent or noncovalent interactions and either with functional groups along the whole chain or at specific endgroups of the polymer chains. However, the polymer brush cannot only immobilize preformed nanoparticles, it is also able to act as a “nanoreactor” where nanoparticles can be formed insitu and are both immobilized and stabilized simultaneously. For catalytic applications this method is especially interesting, because of the absence of any additional stabilizer molecules on the surface of the nanoparticles.

Scheme of the insitu synthesis of catalytically active nanoparticles in P2VP brushes and consecutive UVvis spectra of the reduction of 4-nitrophenol catalyzed by the thus fabricated nanocomposites

Due to their stimuli-responsive swelling behaviour, polymer brushes cannot only be used as sole carriers but also to modulate the properties of the immobilized moieties. The induceable collapse of the polymer brush layer, a diffusional barrier is created, which hinders access of the reactants to the catalyst surface. These coatings therefore show non-Arrhenius like catalytic activity. The performance of these functional coatings can be influenced by variation in the composition of the polymer layer, grafting density and the molecular weight of the applied polymers.

Scheme of the stimuli-responsive catalysis of nanoparticles immobilized in binary brushes with a thermoresponsive component