Scalable Synthesis of Loop Polymer Brush-Grafted Silica-like Nanoparticles from Triethoxysilane-Containing ABA Triblock Copolymers

Cyclic and loop polymer brush-grafted particles have shown promise in applications ranging from drug delivery systems to polymer nanocomposites and imaging contrast agents. We present a scalable method for the synthesis of loop polymer brush-grafted nanoparticles (LB-NPs) with a silica-like core from ABA triblock copolymers via rapid formation of flowerlike spherical micelles using a multi-inlet vortex mixer (MIVM). Two ABA copolymers with outer blocks containing triethoxysilane groups, ABA-20k and -10k, were prepared by atom transfer radical polymerization of 3-(triethoxysilyl)propyl methacrylate from 20 and 10 kDa PEO difunctional initiators, respectively. The polymer solutions in water-miscible organic solvents were rapidly mixed with water via an MIVM, yielding flowerlike micelles, which were cross-linked by adding a catalyst. Methanol was found to be the best organic solvent, and HCl was the most effective in catalyzing the hydrolysis and condensation of triethoxysilane groups in the core of micelles. The PEO loops of LB-NPs were visible in the 1H NMR spectra, and transmission electron microscopy revealed spherical core NPs with rather uniform diameters (∼20 nm). The grafting densities of LB-NPs from ABA-20k and -10k were determined to be 0.13 and 0.16 PEO stem/nm2, respectively, on the core NPs. A larger scale synthesis using a methanol solution of 15 mg/mL ABA-10k yielded LB-NPs essentially identical to those made on a smaller scale. The scalable synthetic method reported here is anticipated to provide fresh opportunities for studying the behaviors of LB-NPs in solution and in bulk and exploring their applications, e.g., in polymer nanocomposites.