pH-Sensitive Polymethacrylates as Potential Contrast Agents in ¹⁹F MRI

¹⁹F MRI is a promising method of diagnosis that can complement the commonly used ¹H MRI with gadolinium contrast agents. Copolymers containing fluoroorganic groups demonstrate many advantages as potential ¹⁹F MRI contrast agents. In this work, a series of copolymers based on 2,2,2-trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFiPMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), or 2-hydroxyethyl methacrylate (HEMA) units are prepared using atom transfer radical polymerization. The highest S/N values in a ¹⁹F NMR spectra is achieved with a copolymer containing 15–25 wt% TFEMA or 18–22 wt% HFiPMA. Copolymers of HFiPMA show a strong effect of pH on T₁ and T₂ relaxation times while only T₂ is significantly affected for the TFEMA copolymers. DFT calculations reveal that the phenomenon is most likely caused by the pH-induced changes in the distance of fluoroorganic groups within a polymer chain.