Tandem Hydroalumination/Oxidation Enables In-Chain Hydroxyl Functionalization of Polydienes.

Abstract

The efficient and facile introduction of polar functionalities into the backbone of nonpolar polydienes remains a longstanding goal in polymer science. However, existing approaches largely rely on functional diene derivatives or multistep post-polymerization functionalization procedures, which often suffer from catalyst deactivation, complex workup, and limited scalability. Herein, we report a tandem hydroalumination/oxidation strategy for the in-chain hydroxyl functionalization of polydienes. Commercially available diisobutylaluminum hydride and metal catalysts enable hydroalumination of C═C bonds to generate reactive C─Al species, which are subsequently converted into hydroxyl groups by in situ oxidation with molecular oxygen. Hydroalumination degrees of up to 26% were achieved and readily tuned by catalyst identity, reagent loading, and temperature, with both hydroalumination and oxidation preferentially occurring at pendant vinyl units. The strategy is applicable to PB, PI, SBR, and butadiene-isoprene copolymers and can be integrated with anionic polymerization to provide a one-pot route directly from butadiene monomer to hydroxyl-functionalized PB. The use of readily available reagents, molecular oxygen as a clean oxidant, and simple workup facilitates practical implementation and future scale-up. The resulting hydroxyl-functionalized polymers further improve silica dispersion and mechanical performance in silica-filled rubber compounds, demonstrating the practical utility of this strategy for functional polydiene materials.