Cationic Bottlebrush Copolymers from Partially Hydrolyzed Poly(oxazoline)s

Cationically charged bottlebrush copolymers were produced by hydrolysis of poly(2-ethyl-2-oxazoline) (PEtOx). The cationic ring-opening polymerization of EtOx was initiated using a styrene derivative to produce PEtOx macromonomers with two different lengths. After detailed characterization, these macromonomers were polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization in a grafting-through process. The length of the bottlebrush backbone was varied, and it was found that a good control over the polymerization could be retained up to backbone DP 50. Hydrolysis of PEtOx repeating units under acidic conditions afforded cationic bottlebrushes, with a defined charge content that could be adjusted by changing the hydrolysis reaction time. Bottlebrush copolymers were analyzed in detail using size-exclusion chromatography, small-angle neutron scattering, and atomic force microscopy indicating a cylindrical topology and an increasing flexibility with increasing chain length.