How tailor-made copolymers can control the structure and properties of hybrid nanomaterials: the case of polyionic complexes

Hybrid polyionic complexes (HPICs) are colloidal structures with a charged core rich in metal ions and a neutral hydrophilic corona. Their properties, whether as reservoirs or catalysts, depend on the accessibility and environment of the metal ions. This study demonstrates that modifying the coordination sphere of these ions can tune the properties of HPICs by altering the composition of the complexing block or varying formulation conditions. Hence, double hydrophilic block copolymers were synthesized using RAFT polymerization, with polyethylene glycol as the neutral block and different ratios of acrylic acid (AA) and vinylphosphonic acid (VPA) as the functional block and further complexed with Fe(III) ions. The resulting iron-based HPICs with higher VPA content were more stable at low pH due to stronger VPA-iron interactions, but their catalytic efficiency in the photo-Fenton process decreased at higher pH. In nanoparticle synthesis, polymers with higher VPA content produced smaller, less-defined Prussian blue nanoparticles, while a 50/50 AA/VPA ratio resulted in uniform nanoparticles and optimal reactivity. Multivariate analysis revealed that not only composition but also local structural organization impacts HPIC properties, influenced by changes in the complexing block structure (<i>e.g.</i>, statistical, block) or formulation conditions.