Synthesis of core-brush fluorescent silica nanoparticles with tunable hydrophilicity by ATRP method

Polymer coating on fluorescent silica nanoparticles enables to tailor made nanocomposite with unique tunable properties. Combining the emission of a fluorescent probe and the surface chemistry of a polymer shell a wide range of applications can be cover. The changing in the conformation of polymer chains enables to modify the hydrophilicity of the functionalized particles. For this, zwitterionic polymers are optimal since the electrostatic interaction between charged groups determines the conformational regime of the chains and the colloidal stability of the particle. In this work, we propose a functionalization of Amino Fluorescent Silica Nanoparticles (Amino-NPF) with a zwitterionic polymer by ATRP method. Poly [2- (Methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide (PDMAPS) was successfully grafted onto the Amino-NPF surface. In particular, we followed three routes with different amount of catalyst. Route 1 corresponds to non-Cu (II) in solution, while pathways 2 and 3 consist of an increment in the metal concentration, 10% and 60% relative to Cu (I), respectively. A very short reaction time, only 15 min, was employed to diminish or avoid radical-radical termination. The stability and dispersability of the obtained core-brush nanoparticles in different solvents was evaluated. We demonstrate that the Cu (II) to Cu (I) concentration ratio defines the conformation of the polymer chains and in turn the hydrophilic character of the particles. [Display omitted] •A zwitterionic polymer shell was successfully grafting from a fluorescent silica core via ATRP method.•The ratio between the activation-deactivating species, Cu(II)/Cu(I), determines the conformational regime of the polymer chains and the graft density.•Nanoparticles with tunable colloidal stability in brine and non-polar media were obtained.