Soft-nanocoupling between silica and gold nanoparticles based on block copolymer

A novel triblock copolymer of ABC type was synthesized by RAFT polymerization with good control and successfully acts as a specific “adhesive” to “glue” the SiO₂ nanoparticles (NPs) and Au NPs together to make a hybrid. This method, with the coined name, soft-nanocoupling, is based on specific anchoring of organic groups onto the surface of inorganic nanoparticles with all-covalent interactions. SiO₂ and Au NPs were used as a proof of concept in this contribution. For the triblock copolymer, namely POE-PGMA-PMPS {poly[oligo(ethylene oxide) methyl ether metharylate]-b-polyglycidyl methacrylate-b-poly[3-(methacryloxypropyl) trimethoxysilane]}, the POE block with oligo-PEG side chains was used to improve the dispersability in solvent media; the PGMA block that was further reacted with lipoic acid was used to anchor onto the Au NPs; and the silane-containing PMPS block can “grab” the SiO₂ NPs. It was found that the resulting SiO₂-Au hybrid has a corona shell of SiO₂ NPs with Au NPs tightly embedded inside, and can even tolerate a harsh sonication process of 1 h. Since the soft triblock copolymer functions as a bridge to couple Au and SiO₂ NPs together, the process is called soft-nanocoupling. Compared to the conventional hard-coupling process, which requires specific case by case procedures, soft-nanocoupling is more straightforward, and especially can be designed in a modular way depending on the specific NPs used. With the well-established synthetic methodologies of NPs of single components to date, such as SiO₂, Au, Fe_xO_y etc., all that is needed to make hybrid NPs is the proper design of a specific “glue” with anchoring moieties targeting the selected NPs. Thus, the soft-nanocoupling methodology affords a new platform for fabricating hybrid nano-objects from NPs using block copolymers.