Polyoxazoline adsorption on silica nanoparticles mediated by host–guest interactions

The objective of this work is to develop an original method of polyoxazoline brush generation based on supramolecular chemistry onto silica nanoparticles. A first layer is realized by adsorption of a polymer bearing β-cyclodextrin units (PβCD). This allows the anchoring of a second layer made of alkyl end-capped poly(2-methyl-2-oxazoline) (POXZ–Cn) via host–guest interactions between the alkyl end groups and the β-cyclodextrin units. The characteristics of the surface layers were studied by dynamic light scattering. A first study of PβCD adsorption allowed to define the conditions of homogeneous PβCD coverage onto the silica surfaces. Then the adsorption of the second polymer onto the PβCD coated nanoparticles was studied as a function of the POXZ–Cn solution concentration. Brush layers with chains in extended conformation could be obtained above a critical POXZ–Cn concentration. The large thickness sensitivity to the feeding POXZ–Cn concentrations allowed to show that the POXZ–Cn grafting ratio can be controlled by the POXZ–Cn concentrations. In a limited concentration range, the nature of the anchoring end-group (C12 or C18) does not influence the shape of the POXZ layer.