Facile approach to functionalize nanodiamond particles with V-shaped polymer brushes

Nanodiamond (ND) particles were functionalized with V-shaped polymer brushes of polystyrene and poly(t-butyl methacrylate) (PtBMA) through the reaction of surface carboxylic groups of NDs toward epoxy functionalities located in the middle of the polymer precursor, an ABC-type triblock copolymer. The block copolymer was prepared through sequential radical polymerizations of tBMA, glycidyl methacrylate (GMA), and styrene mediated by a reversible addition-fragmentation chain transfer process, in which the lengths of different segments are well-controlled by virtue of the living nature of the reaction. The polymerization product, PtBMA-b-PGMA-b-PS, carried a short block of PGMA in the middle, which was used for subsequent reaction with -COOH on the convex surface of the NDs. This grafting-onto approach through a center-linking process functionalized nanoparticles with V-shaped polymer brushes possessing an exact 1: 1 molar ratio of different arms. Furthermore, ND particles with amphiphilic functionalities were prepared after hydrolysis of the PtBMA segment. The obtained polymer grafted ND was characterized by electron microscopy (TEM and SEM), NMR and IR spectroscopy, and TGA. The product not only formed stable dispersions in organic solvents such as tetrahydrofuran, toluene, and chloroform but also self-assembled at oil-water interfaces to form flat films or large droplets of water-in-oil and oil-in-water. The mechanism of self-assembly at liquid-liquid interfaces is discussed.