Temperature and pH dual-responsive cross-linked polymeric nanocapsules with controllable structures via surface-initiated atom transfer radical polymerization from templates

Novel intelligent nanocapsules with temperature-responsive cross-linked polymer shells and pH-responsive polymer brushes on their inner walls were designed by the "polymerization from template" strategy via the surface-initiated atom transfer radical polymerization (SI-ATRP) technique using silica nanoparticles as the templates. The two-step sequential SI-ATRP procedures provided poly(tert-butyl acrylate) brushes on the inner walls of temperature-responsive cross-linked poly(N-isopropyl acrylamide) shells. Then the tert-butyl ester groups in the nanocapsules were transformed chemically into acrylic acid groups after the silica templates had been etched with hydrofluoric acid. The hollow structures and the multiple environmental stimuli-responsive properties were validated with transmission electron microscopy and dynamic light scattering techniques, respectively. In the strategy developed, the inner diameter, the cross-linking degree and the thickness of the shells, and the length of the functional brushes could be controlled by adjusting the preparation conditions. From the Clinical Editor: This basic science paper discusses the synthesis and functions of novel intelligent nanocapsules with temperature-responsive cross-linked polymer shells and pH-responsive polymer brushes on their inner walls. (C) 2011 Elsevier Inc. All rights reserved.