Leveraging the Enantiomeric Excess of Catalyst for Precise Stereocontrol in Poly(3‐hydroxybutyrate)

ABSTRACT The properties of polymers are governed by multi‐level structural parameters, with tacticity being particularly critical for crystallization, thermal, and mechanical performance. Conventional approaches to modulate tacticity—such as tuning monomer enantiomeric excess or synthesizing distinct catalysts—are often complex and lack precise control. To address this challenge, we present a stereocontrol strategy by exploiting an enantiopure catalyst governed by an enantiomorphic site control (ESC) mechanism and polymeric exchange between the enantiomer pair. As a result, the enantiopure DiMeBiPh‐BINOL‐salen catalysts ( R , R )‐ Y1 and ( S , S )‐ Y1 were designed and demonstrated outstanding isoselectivity for the ROP of rac ‐BBL via the ESC mechanism. Their racemic pair rac ‐ Y1 exhibited high syndioselectivity ( P r = 0.93) due to polymeric exchange. Ultimately, a series of P3HB products with streamlined tacticity ( P m : 0.07−0.90) was readily prepared by simply adjusting the enantiomeric excess (ee) values of the catalyst. A systematic investigation of the relationship between tacticity and material properties was performed. This work not only establishes an efficient and controllable route to tailor‐made P3HB but also provides a scalable pathway for precise stereocontrol in polymer synthesis.