Preparation of oxazoline-group-functionalized diamond using poly (2-vinyl-2-oxazoline) based on a model reaction between oxazoline and carboxylic acid

We conducted research aimed at combining diamond particle surfaces with external moieties using a polymer. We here propose an effective solution using a reactive polymer, poly (2-vinyl-2-oxazoline) (Pvozo), with a large amount of reactive oxazoline as side chains. The idea is that some of the oxazoline groups react with carboxylic acid at the surface and the other oxazoline groups remain as available unreacted groups for further reaction with external moieties. The chemical reactivity of oxazoline with carboxylic acid was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy using model low-molecular-weight molecules, followed by reaction between Pvozo and the surface. The amount of acid groups on the surface was determined by titration. Diamond particles reacted with Pvozo in a solvent, followed by a washing step, which resulted in the formation of a uniform monolayer of nanosized Pvozo on micron-sized diamond particles, which was confirmed by thermogravimetric analysis (TGA) and by a visible-marker method with scanning electron microscopy (SEM) using carbon nanotubes. The amounts of reacted and unreacted oxazoline of Pvozo on the surface were quantified using nonanoic acid in conjunction with TGA.