Toward Ultimate Control of Radical Polymerization: Functionalized Metal–Organic Frameworks as a Robust Environment for Metal-Catalyzed Polymerizations

Hui-Chun Lee, Jongkook Hwang, Uwe Schilde, Markus Antonietti, Krzysztof Matyjaszewski, Bernhard V. K. J. Schmidt

Index: 10.1021/acs.chemmater.8b00546

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Abstract

Herein, an approach via combination of confined porous textures and reversible deactivation radical polymerization techniques is proposed to advance synthetic polymer chemistry, i.e., a connection of metal–organic frameworks (MOFs) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Zn2(benzene-1,4-dicarboxylate)2(1,4-diazabicyclo[2.2.2]octane) [Zn2(bdc)2(dabco)] is utilized as a reaction environment for polymerization of various methacrylate monomers (methyl, ethyl, benzyl, and isobornyl methacrylate) in a confined nanochannel, resulting in polymers with control over dispersity, end functionalities, and tacticity with respect to distinct molecular size. To refine and reconsolidate the compartmentation effect on polymer regularity, initiator-functionalized Zn MOF was synthesized via cocrystallization with an initiator-functionalized ligand, 2-(2-bromo-2-methylpropanamido)-1,4-benzenedicarboxylate (Brbdc), in different ratios (10%, 20%, and 50%). Through the embedded initiator, surface-initiated ARGET ATRP was directly initiated from the walls of the nanochannels. The obtained polymers had a high molecular weight up to 392 000. Moreover, a significant improvement in end-group functionality and stereocontrol was observed, entailing polymers with obvious increments in isotacticity. The results highlight a combination of MOFs and ATRP that is a promising and universal methodology to prepare various polymers with high molecular weight exhibiting well-defined uniformity in chain length and microstructure as well as the preserved chain-end functionality.