Tetra-hydropyrimidin-2-ylidene-Based Lewis Pair Polymerization to Access Alkyl (Meth)acrylate Polymers with Tunable Topology and High Performance

Abstract

Developing cost-effective and highly efficient Lewis pair (LP) systems represents a powerful strategy for achieving living/controlled polymerization of (meth)acrylates, enabling the synthesis of functional polar vinyl polymers with diverse structures and topologies. Herein, a new class of strong nucleophilic tetra-hydropyrimidin-2-ylidenes (THPEs) bearing mono-, dual-, tri-, tetra-, and hexa-initiating units was successfully synthesized on a multigram scale in a two-step synthetic procedure. By combining with bulky and modestly acidic Lewis acids, a series of multi-initiating THPE-based LP systems were effectively prepared for the living polymerization of methyl methacrylate (MMA), thus affording the corresponding polymers with predicted molecular weight (Mn up to 285.3 kg mol–1), narrow dispersity value (Ð as low as 1.08), and tunable topology (2-, 3-, 4- and 6-arm). Furthermore, by integrating these multi-initiating LP systems with the unique compounded sequence control strategy, one-step polymerization of MMA or isobornyl methacrylate (IBOMA) with 2-methoxyethyl acrylate (MEA) was developed for the synthesis of all-(meth)acrylic triblock thermoplastic elastomers with diverse topologies and well-defined sequences. Mechanical investigations demonstrated that 3-arm star-shaped elastomers significantly outperformed other topological architectures in both tensile strength and elongation at break, while IBOMA-derived elastomers exhibited superior service temperatures and enhanced elastic recovery compared to their MMA-derived counterparts.