Synthesis of metal-complexing nanoparticles by post-functionalisation of reactive nanolatexes produced by microemulsion polymerisation

Metal-complexing nanoparticles, with average diameters ranging from 15 to 25 nm, are prepared using a two-step procedure: synthesis of reactive nanoparticles followed by post-functionalisation with a selective macrocyclic ligand, cyclam (tetraazacyclotetradecane). The starting nanoparticles, containing benzylhalide reactive groups are readily prepared by copolymerisation of vinylbenzylchloride in ternary oil-in-water microemulsions stabilized by a cationic surfactant (dodecyltrimethyl ammonium bromide). Elemental analyses of the polymer reveals that exchange of chlorine for bromine as well as hydrolysis of chloromethyl residues occur within the reaction medium, the rate of both side reactions being dependent upon the experimental conditions. The overall content of reactive chloro- and bromobenzyl moieties range from 0.7 to 1.1 mmol g –1 . Reaction of cyclam, performed directly in the aqueous suspensions, gives rise to stable suspensions of functionalised nanoparticles containing 0.2 to 0.3 mmol ligand g –1 . Spectrophotometric measurements show that these cyclam post-functionalized nanoparticles exhibit a ‘solution-like’ complexation behaviour thus demonstrating remarkable ligand accessibility.