Thermally Responsive Unimolecular Nanoreactors from Amphiphilic Dendrimer-Like Copolymer Prepared via Anionic Polymerization and Cross Metathesis Reaction

Amphiphilic dendrimer-like polymers are expected to be promising candidates as micro containers or carriers due to their much larger size in relative to regular dendrimers. In the present study, we synthesize amphiphilic dendrimer-like copolymers possessing interior poly(styrene) segments and peripheral poly(ethylene oxide) (PEO) segments through iterative anionic polymerization, hydrosilylation, coupling, followed by olefin cross-metathesis with a PEO macromonomer bearing acrylic terminus (denoted as PEGMEA480). The molecular weight of the resulting dendrimer-like copolymer, G3-g-PEO2900, is as large as 2.16 × 106, with number of outer PEO arms up to 2900, and the average diameter 32.8 nm in solution. The behavior of the dendritic product as unimolecular micelles is investigated, using dynamic light scattering (DLS) and pyrene probing, together with the thermal responsiveness arising from the low critical solution temperature (LCST) of PEO segments. The amphiphilic dendrimer-like copolymers are used as nanoreactors for the nucleophilic displacement of benzyl halide by KSCN and the hydrolysis reaction of benzyl halide, in which significant increases in the reaction yields are observed. More interestingly, the nanoreactor can be regulated activation-and-deactivation due to thermoresponsiveness of peripheral PEO segments, and the dendritic nanoreactor is recyclable for at least 7 times.