Abstract
The use of fluorinated contrast agents in magnetic resonance imaging (MRI) facilitates improved image quality due to the negligible amount of endogenous fluorine atoms in the body. In this work, we present a comprehensive study of the influence of the amphiphilic polymer structure and composition on its applicability as contrast agents in 19 F MRI. Three series of novel fluorine-containing poly(2-oxazoline) copolymers and terpolymers, hydrophilic–fluorophilic, hydrophilic–lipophilic–fluorophilic, and hydrophilic–thermoresponsive–fluorophilic, with block and gradient distributions of the fluorinated units, were synthesized. It was discovered that the CF 3 in the 2-(3,3,3-trifluoropropyl)-2-oxazoline (CF 3 EtOx) group activated the cationic chain end, leading to faster copolymerization kinetics, whereby spontaneous monomer gradients were formed with accelerated incorporation of 2-methyl-2-oxazoline or 2- n -propyl-2-oxazoline with a gradual change to the less-nucleophilic CF 3 EtOx monomer. The obtained amphiphilic copolymers and terpolymers form spherical or wormlike micelles in water, which was confirmed using transmission electron microscopy (TEM), while small-angle X-ray scattering (SAXS) revealed the core–shell or core–double-shell morphologies of these nanoparticles. The core and shell sizes obey the scaling laws for starlike micelles predicted by the scaling theory. Biocompatibility studies confirm that all copolymers obtained are noncytotoxic and, at the same time, exhibit high sensitivity during in vitro 19 F MRI studies. The gradient copolymers provide the best 19 F MRI signal-to-noise ratio in comparison with the analogue block copolymer structures, making them most promising as 19 F MRI contrast agents.