Heteronuclear, Monomer-Selective Zn/Y Catalyst Combines Copolymerization of Epoxides and CO2 with Group-Transfer Polymerization of Michael-Type Monomers.

Abstract

Terpolymerizations of cyclohexene oxide (CHO), CO2, and the Michael-type monomer 2-vinylpyridine (2VP) are presented. The combination of two distinct polymerization mechanisms was enabled by the synthesis of a heterobifunctional complex (3). Its β-diiminate zinc moiety allows the ring-opening copolymerization of CHO and CO2, whereas the yttrium metallocene catalyzed the rare earth metal-mediated group-transfer polymerization of the polar vinyl monomer. Both units were connected via the CH-bond activation of a pyridyl-alkoxide linker. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) revealed the successful transfer of the linker to the end-group of the respective homopolymers poly(cyclohexene carbonate) (PCHC) and poly(2VP) (P2VP) being the prerequisite for copolymer formation. Aliquot gel-permeation chromatography (GPC) analysis and solubility behavior tests confirmed the P2VP-block(b)-PCHC terpolymer formation via two pathways, a sequential and a one-pot procedure. Furthermore, the versatility of the method was demonstrated by introducing 2-isopropenyl-2-oxazoline (IPOx) as the second Michael-type monomer that yielded the terpolymer poly(IPOx)-b-PCHC.