The living cationic ring-opening polymerization of 2-oxazolines (see Figure) has been studied in great detail since its discovery in 1966. The versatility of this polymerization method allows copolymerization of a variety of 2-oxazoline monomers to give a range of tunable polymer properties that enable, for example, hydrophilic, hydrophobic, fluorophilic, as well as hard and soft materials. However, this class of polymers was almost forgotten in the 1980s and 1990s because of the long reaction times and limited application possibilities. In the new millennium, a revival of poly(2-oxazoline)s has arisen because of their potential use as biomaterials and thermoresponsive materials, as well as the easy access to defined amphiphilic structures for (hierarchical) self-assembly.<br/><br/>Recent developments from our research group that broaden the scope of poly(2-oxazoline)s will be discussed in this lecture, focusing on the (co)polymerization of larger cyclic imino ethers, such as 2-oxazines and 2-oxazepines. It was unexpectedly found that copolymerization of 2-oxazolines with 2-oxazines yields gradient copolymers in which the 2-oxazine is incorporated faster. In contrast, during homopolymerization the 2-oxazolines polymerize faster than the 2-oxazines. This difference between the homopolymerizations and copolymerizations will be discussed based on the combination both electronic and steric effects. Finally, the synthesis and homopolymerization of 2-phenyl-2-oxazepine will be discussed revealing significantly slower homopolymerization than the corresponding 2-phenyl-2-oxazoline and 2-phenyl-2-oxazine.

Poly(cyclic imino ether)s beyond 2-oxazolines

2019 Spring National Meeting

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