Unidirectional Chain Transfer of Enol Ethers Yields Heterotelechelic Degradable Poly(Enol Ether)

In ring opening metathesis polymerization (ROMP), vinyl and enol ethers have been predominantly used to terminate the polymerization. However, contrary to convention, we have previously reported ROMP of a cyclic enol ether, 2,3-dihydrofuran, to give an acid degradable poly(enol ether). Herein, we describe the use of linear, hetero bifunctional enol ethers as chain transfer agents to synthesize heterotelechelic poly(enol ether). Unidirectional chain transfer was achieved by leveraging regioselective addition of enol ethers to the Grubbs complexes. Excellent regioselectivity in producing the desired heterotelechelic polymers was confirmed by high-resolution mass spectroscopy and NMR spectroscopy. We demonstrate various tranformations of the end group functionalities without causing unwanted degradation of the poly(enol ether) backbone. The end group functionalities were also used to synthesize fully degradable block copolymers, where each block can be degraded under orthogonal conditions. The unique unidirectional chain transfer allows for the installation of functionalities at one or both chain ends, facilitating further applications of readily synthesized poly(enol ether) as a sustainable polymer.