Miniemulsion SI-ATRP by Interfacial and Ion-Pair Catalysis for the Synthesis of Nanoparticle Brushes
Rongguan Yin, Paweł Chmielarz, Izabela Zaborniak, Yuqi Zhao, Grzegorz Szczepaniak, Zongyu Wang, Tong Liu, Yi Wang, Mingkang Sun, Hanshu Wu, Jirameth Tarnsangpradit, Michael R. Bockstaller, Krzysztof Matyjaszewski
Abstract
Densely grafted polymer/inorganic nanoparticle hybrids were synthesized via a surface-initiated activator regenerated by electron transfer (SI-ARGET) atom transfer radical polymerization (ATRP) of n-butyl acrylate (BA) under ion-pair and interfacial catalysis in miniemulsion (hydrodynamic diameters from 105 to 128 nm) with ascorbic acid (AsAc) as the reducing agent. The use of a single-catalyst system in dispersed media allowed the preparation of hybrid materials using a very low catalyst loading (as low as 100 ppm of [Br-CuII(L)]+ relative to monomer) and obtaining high monomer conversion (up to 70%) without macroscopic gelation. The resulting polymers exhibited narrow molecular weight distributions (Đ ≤ 1.31), and the polymer-grafted nanoparticles showed excellent size uniformity. Dispersions in organic solvents (e.g., tetrahydrofuran) were stable without any particle aggregations. Subsequent chain extension of the particle brushes with tert-butyl acrylate (tBA) proved the livingness of the polymerization and high retention of chain-end fidelity. The developed miniemulsion SI-ARGET ATRP technique with interfacial and ion-pair catalysis offers numerous advantages for the preparation of nanoparticle brushes over the traditional hydrophobic ATRP process. These include a high monomer conversion, high grafting density, better control over polymerization rate, high chain-end livingness, and the use of a very low amount of copper catalyst.