Chemoselective RAFT Polymerization of a Trivinyl Monomer Derived from Carbon Dioxide and 1,3-Butadiene: From Linear to Hyperbranched

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL), a substituent delta-lactone synthesized through telomerization of CO2 with 1,3-butadiene, is highly functionalized containing a six-membered ring and two vinyl groups. It can hardly be polymerized directly through common methods due to its poor polymerizability. In this paper, we report the controlled polymerization of a highly reactive trivinyl monomer derived from EVL, i.e. methyl-2-ethylidene-S-hydroxyhept-6-enoate methacrylate (MEDMA), which is synthesized through ring cleavage of EVL and subsequent esterification with methacryloyl chloride. Chemoselective RAFT polymerizations of MEDMA mediated by 2-cyanoprop-2-yl-dithiobenzoate (CPDB) are achieved and well-defined polymers with linear and hyperbranched topologies are obtained under optimized polymerization conditions. RAFT polymerizations show good control in producing linear PMEDMAs with predetermined molecular weights (4000 g/mol) and moderate polydispersity indices (below 1.22). The resultant hyperbranched PMEDMAs are fully characterized by H-1 NMR, C-13 NMR, H-1-C-13 HMQC, DEPT, DLS, and TEM. The incorporations of vinyl group in allylic ester into polymer chains lead to the hyperbranched topology. Both PMEDMAs are ready for the introduction of amino and carboxy groups through thiol-ene click chemistry, and the products self-assemble to the micelles with different morphologies. This protocol develops the utilization of EVL in synthetic polymers and is significant to the carbon dioxide transformation.