Phosphonic Acid-Functionalized Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly: Synthesis, Characterization, and Occlusion into Calcite Crystals

Dialkylphosphonate-functionalized and phosphonic acid-functionalized macromolecular chain transfer agents (macro-CTAs) were utilized for the reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) at 20% w/w solids in methanol at 64 °C. Spherical, worm-like and vesicular nano-objects could all be generated through systematic variation of the mean degree of polymerization of the core-forming PBzMA block when using relatively short macro-CTAs. Construction of detailed phase diagrams is essential for the reproducible targeting of pure copolymer morphologies, where these were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). For nano-objects prepared using the phosphonic acid-based macro-CTA, transfer from methanol dispersion to water leads to the development of anionic surface charge as a result of ionization of the stabilizer chains, but this does not adversely affect the copolymer morphology. Given the well-known strong affinity of phosphonic acid for calcium ions, selected nano-objects were evaluated for their in-situ occlusion within growing CaCO3 crystals. Scanning electron microscopy (SEM) studies provide convincing evidence for the occlusion of both worm-like and vesicular phosphonic acid-based nano-objects and hence the production of a series of interesting new organic-inorganic nanocomposites.