Versatile side chain modification via isocyanide-based multicomponent reactions: tuning the LCST of poly(2-oxazoline)s

Poly(2-oxazoline)s are receiving large current interest based on their potential use in biomedical applications. The development of novel methods to control the polymer side chains and to tune the polymer properties will further enhance this potential. In this contribution, the Passerini and Ugi multicomponent reactions are used to modify a random poly(2-oxazoline) copolymer of 2-ethyl-2-oxazoline (EtOx) and 2-methyl butyrate-2-oxazoline (C3-MestOx) with defined chain length and comonomer ratio. Hydrolysis of the pending methyl ester groups provided an easy access to carboxylic acid groups in the side chain, which were used for post-polymerization modification reactions via isocyanide-based multicomponent reactions (IMCRs) to simultaneously introduce various substituents. This allowed a straightforward adjustment of the properties of the random poly(2-oxazoline). Most importantly, control over the cloud point and glass transition temperatures was possible by simple variation of the components used in the multicomponent grafting approach.