Synthesis of Breathing Metallopolymer Hollow Spheres for Redox-Controlled Release

A convenient synthetic approach for the preparation of uniform metallopolymer-containing hollow spheres based on 2-(methacryloyloxy)ethyl ferrocenecarboxylate (FcMA) as monomer by sequential starved feed emulsion polymerization is described. Core/shell particles consisting of a noncrosslinked poly(methyl methacrylate) core and a slightly crosslinked ferrocene-containing shell allows for the simple dissolution of core material and, thus, monodisperse metallopolymer hollow spheres are obtained. Since PFcMA is incorporated in the particle shell, herein investigated hollow spheres can be addressed by external triggers, i.e., solvent variation and redox chemistry in order to change the particle swelling capability. PFcMA-containing core/shell particles and hollow spheres are characterized by transmission electron microscope (TEM), scanning electron microscopy, cryogenic TEM, thermogravimetric analysis, and dynamic light scattering in terms of size, size distribution, hollow sphere character, redox-responsiveness, and composition. Moreover, the general suitability of prepared stimulus-responsive nanocapsules for the use in catch-release systems is demonstrated by loading the nanocapsules with malachite green as model payload followed by release studies.