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

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.