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

F-19 MRI is a promising method of diagnosis that can complement the commonly used H-1 MRI with gadolinium contrast agents. Copolymers containing fluoroorganic groups demonstrate many advantages as potential F-19 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 F-19 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 T-1 and T-2 relaxation times while only T-2 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.