Dynamic Supramolecular Helicity in a Multi-Aluminum Porphyrin Catalyst Enables Stereocontrolled Synthesis of Ultrahigh-Molecular-Weight Isotactic Poly(propylene oxide)

Abstract

Isotactic poly(propylene oxide) (iPPO) is a robust polyether with photodegradability. However, its stereoselective synthesis from racemic propylene oxide (rac-PO) remains dominated by preconfigured axially chiral cobalt/chromium bimetallic catalysts. Here, we report an ion pair-assisted dynamic helical organization strategy employing a bifunctional multi-aluminum porphyrin (BMAlP) catalyst for stereocontrolled synthesis of iPPO. This approach affords highly isotactic PPO with [mm] up to 97.6%, ultrahigh viscometric molecular weight (Mv up to 6700 kDa), and a tensile strength of 92 MPa comparable to nylon-66. Mechanistic studies reveal that π–π interactions among polyacrylate-supported porphyrin generate dynamic P/M helical organizations, while ion pairs stabilize hierarchical organization and promote cooperative aluminum-site arrangement, creating locally persistent enantiomorphic catalytic environments for enantiomorphic-site-controlled PO insertion. This work establishes dynamic supramolecular chirality as an alternative strategy for stereoselective polymerization beyond static molecular chirality.