Fluorinated 2-Alkyl-2-oxazolines of High Reactivity: Spacer-Length-Induced Acceleration for Cationic Ring-Opening Polymerization As a Basis for Triphilic Block Copolymer Synthesis

The synthesis of defined triphilic terpolymers with hydrophilic, lyophilic, and fluorophilic blocks is an important challenge as a basis for the development of multicompartment self-assembled structures with potential for, e.g., cascade catalysis and multidrug loading. The synthesis of fluorophilic poly(2-oxazoline)s generally suffers from a very low reactivity of fluorinated 2-oxazoline monomers in cationic ring-opening polymerization (CROP). We report a systematic study on overcoming the extremely low reactivity of 2-perfluoroalkyl-2-oxazolines in CROP by the insertion of methyl and ethyl hydrocarbon spacers between the 2-oxazoline ring and the trifluoromethyl group. The kinetic studies showed the gradual increase of the rate of polymerization with increasing of the hydrocarbon spacer length. The monomer with an ethyl spacer was found to have similar reactivity as 2-alkyl-2-oxazolines and allowed the synthesis of defined triphilic triblock copolymers.