Synthesis and evaluation of partly fluorinated polyelectrolytes as components in 19F MRI-detectable nanoparticles

A series of partly fluorinated polyelectrolytes were synthesized by transition metal mediated living radical polymerization and evaluated for their applicability as corona-forming components in 19F MRI-detectable nanoparticles in aqueous solutions. The polymers were statistical and block copolymers of trifluoroethyl methacrylate (TFEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The polymers were either directly dissolved in water (statistical copolymers), or assembled into aqueous nanoparticles with PTFEMA cores and P(TFEMA-co-DMAEMA) coronas (block copolymers). The polymer composition, polymer charge density, solution ionic strength and solution pH were varied. The 19F spin–lattice (T1) and spin–spin (T2) relaxation times and 19F image intensities of solutions of the polymers were measured and related to polymer structure and aqueous conformation. The 19F NMR T2 relaxation times were found to be highly indicative of the 19F imaging performance. Maintaining sufficient mobility of the 19F nuclei was important for obtaining images of high intensity. 19F mobility could be increased by preventing their aggregation in water by exploiting electrostatic repulsion between monomer units.