Toward the preparation of polymers without residual metal contamination, metal-free ring-opening metathesis polymerization (MF-ROMP) utilizing organic photoredox mediators has emerged as an alternative to traditional metal-based ROMP. Instead of using metal-based initiators, the photoredox-mediated MF-ROMP protocol uses vinyl ethers as organic initiators. Since vinyl ether moieties can be easily installed via simple organic transformations, we believe that the photoredox-mediated MF-ROMP, aside from its inherent metal-free merits, can also provide opportunities to develop expedient synthetic approaches toward controlling macromolecular architectures. This is crucial in shaping both physical and chemical properties of the obtained polymers. Herein, we describe our recent efforts in preparing polymers with various macromolecular architectures by photoredox-mediated MF-ROMP grafting from both multifunctional small molecular initiators and macroinitiators. The research began with the study of bidirectional MF-ROMP, which could have either inward or outward polymer growth depending on different relative orientation of alkoxy moieties in divinyl ethers. Based on the evaluation of inward-growing polymers versus outward-growing polymers, the incorporation of monomers was successful both at chain-end and chain-centered active site. The use of macroinitiators derived from PPG, PEG and polystyrene also allows the rapid access to acid-cleavable copolymers, which might be useful for future application.

Toward engineering macromolecular architectures of polymers through photoredox-mediated metal-free ring-opening metathesis polymerization

255th National Meeting (2018)

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