Poly(2-oxazoline)s (PAOx) are readily made by the cationic ring opening polymerization (CROP) providing direct access to well defined polymers with a broad range of architectures. Not only the structure can be tuned, but more importantly, also the polymer properties, such as thermoresponsive lower critical solution temperature (LCST) behavior. For further applications the introduction of functionalities is important. The functionalisation of PAOx can be achieved via four different pathways, namely through initiation, termination, functional monomers and post-polymerization modification. In this work, we will discuss our endeavors to functionalize PAOx via termination as well as side chain post-modification. The functionalization of PAOx via termination is based on the efficient end-capping of the living PAOx chains with deprotonated carboxylic acids, thiolates and amines that act as nucleophilic terminating agents. In this way different functionalities have been introduced, such as reactive groups for further (click) modification, including thiols and amines and reactive dyes. The second developed method for side-chain post-modification of PAOx is based on the introduction of methyl ester groups in the side chain, either via copolymerization of a methyl ester containing 2-oxazoline monomer or by partial hydrolysis of the PAOx followed by modification of the resulting secondary amine groups with different linkers such as bromo acetate, methyl-chlorosuccinate and methoxycarbonylethyliso(thio)cyanate. It will be demonstrated that these side chain methyl ester groups can be easily reacted with amines in a transamidation step to introduce a wide variety of functional groups such as acid, amine, alcohol, hydrazide and propargyl groups. Finally, the secondary amine groups in the main chain of partially hydrolyzed PAOx are also utilized for the introduction of side chain sugars by reductive amination.

Functionalization of poly(2-oxazoline)s by post-polymerization modification of side chains and end-groups

248th National Meeting (2014)

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