Self-assembly of block copolymers with an alkoxysilane-based core-forming block: a comparison of synthetic approaches

Polymerization-induced self-assembly (PISA) has become the preferred method of preparing self-assembled nano-objects based on amphiphilic block copolymers. The PISA methodology has also been extended to the realization of colloidal nanocomposites, such as polymer–silica hybrid particles. In this work, we compare two methods to prepare nanoparticles based on self-assembly of block copolymers bearing a core-forming block with a reactive alkoxysilane moiety (3-(trimethoxysilyl)propyl methacrylate, MPS), namely (i) RAFT emulsion polymerization using a hydrophilic macroRAFT agent and (ii) solution-phase self-assembly upon slow addition of a selective solvent. Emulsion polymerization under both ab initio and seeded conditions were studied, as well the use of different initiating systems. Effective and reproducible chain extension (and hence PISA) of MPS via thermally initiated RAFT emulsion polymerization was compromised due to the hydrolysis and polycondensation of MPS occurring under the reaction conditions employed. A more successful approach to block copolymer self-assembly was achieved via polymerization in a good solvent for both blocks (1,4-dioxane) followed by the slow addition of water, yielding spherical nanoparticles that increased in size as the length of the solvophobic block was increased.