DL‐Methionine‐Mediated PET‐RDRP: A Route to Low‐Molecular‐Weight Polyacrylic Acid for Effective Scale Inhibition

ABSTRACT Low‐molecular‐weight polyacrylic acid (LMW‐PAA) is a water‐soluble, phosphorus‐free scale inhibitor. Current industrial production employs chain transfer agents for molecular weight control, but this approach often yields products with wide molecular weight distributions. To address this limitation, photoinduced electron/energy transfer‐reversible deactivation radical polymerization (PET‐RDRP) is employed as an effective method for preparing polymers with controllable molecular weights. In this study, LMW‐PAA is prepared through DL‐methionine (DL‐Met)‐mediated photopolymerization catalyzed by zinc protoporphyrin (ZnPP) in dimethyl sulfoxide (DMSO). Precise control over molecular weight and its distribution is achieved. Polymerization conditions are examined at room temperature by varying the concentrations of DL‐Met and ZnPP. The optimal acrylic acid (AA): DL‐Met: ZnPP molar ratio is identified as 1400.00:33.74:1.00. The resulting LMW‐PAA exhibits a number‐average molecular weight ( M n ) of 450 g·mol −1 and a dispersity ( Đ ) of 1.049. Furthermore, the polymerization demonstrates responsiveness to external light switching, and the synthesized LMW‐PAA effectively inhibits scaling caused by both CaCO 3 and CaSO 4 .