Multifactor Control of Vinyl Monomer Sequence, Molecular Weight, and Tacticity via Iterative Radical Additions and Olefin Metathesis Reactions

Monomer sequence control in terms
of a single monomer unit, particularly
in vinyl polymers, is one of the largest challenges in polymer chemistry.
Furthermore, multifactor control of monomer sequence, molecular weight,
and stereoregularity is an ultimate goal. In this work, we propose
a strategy to prepare C–C main-chain sequence-regulated polymers
with controlled molecular weights from vinyl monomers via a combination
of iterative atom transfer radical additions and olefin metathesis
reactions. This strategy enabled the synthesis of sequence-regulated
polymers with exact styrene–acrylate–styrene sequences
in the C–C main chains, controlled molecular weights of up
to 104, and stereoregularities varying with syndiotacticity,
isotacticity, and heterotacticity. The utility of this strategy is
further demonstrated by formation of block copolymers consisting of
sequence-regulated vinyl polymer segments by combining living ROMP
of norbornene derivatives.