Well-defined tertiary amine-based methacrylate pH-responsive homopolymers and block copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using a dithioester or trithiocarbonate based RAFT agent for homopolymers and poly(ethylene glycol) (PEG) macro-RAFT agents for block copolymers. <sup>1</sup>H NMR and gel permeation chromatography results confirmed the successful synthesis of these homopolymers and block copolymers. A detailed study of the polymerization kinetics for each of these systems indicated that the formation of both the homopolymers and the block copolymers were well defined. The pH-responsive properties of these homopolymers and block copolymers were also studied by determining the pKa values using titration-based techniques and also monitoring the hydrodynamic volume and zeta potential of the polymers in solution via dynamic light scattering (DLS). The pKa titration experiments suggested that the homopolymers and the related block copolymers have a similar pKa. The DLS investigation showed that all of the block copolymers underwent a sharp transition from unimers to micelles around their pKa and the hydrodynamic diameter (D<sub>h</sub>) was not only depended on the molecular weight but also on the composition of the block copolymers. These copolymers have then been used to modify gadolinium (Gd) nanoparticles to design a smart contrast agent for magenetic resonance imaging (MRI), which will potentially allow for enhanced diagnostics in the treatment of cancer.

RAFT polymerization of tertiary amine-based methacrylate pH-responsive monomers for smart MRI contrast agents

249th National Meeting (2015)

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