Stereoselective Living Coordination and Chain Transfer Polymerization of Kempe’s 4-Ethyl-1-alkenes

A toolbox of living coordination polymerization (LCP) processes mediated by cyclopentadienyl, amidinate (CPAM) group 4 metal ion pair initiators has been used to convert a family of branched 4-ethyl-1-alkenes, which are now readily accessible in practical quantities through Kempe’s titanium-mediated bis-homologation of linear 1-alkenes with ethene, into isotactic and atactic (iso-rich) forms of the corresponding poly(4-ethyl-1-alkene)s (P4E1As). Application of living coordinative chain transfer polymerization (LCCTP) of these same monomers, in which diethylzinc is employed as a reversible chain transfer agent, further permitted production of scalable quantities of ultralow-molar-mass, end-group-functionalized P4E1As of narrow dispersity (Đ ≤ 1.15) and with targeted DPn values of only 12–13. These highly branched x-P4E1As are of interest as a potential class of “globular” hydrophobic domain building blocks.