The benzaldehyde derivatives, such as 2,4-dimethoxy benzaldehyde (PC1) and p-anisaldehyde (PC2), were successfully used as photoredox catalysts (PCs) in combination with typical RAFT agent 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CTP) for the controlled photoinduced electron transfer RAFT polymerization (PET-RAFT) of methyl methacrylate (MMA) and benzyl methacrylate (BnMA) at room temperature. The kinetics of the polymerizations showed first order with respect to monomer conversions. Besides, the average number molecular weights (M-n) of the produced polymers increased linearly with the monomer conversions and kept relatively narrow polydispersity (PDI=M-w/M-n). For example, the M-n of PMMA increased from about 3400 to 17,300 g mol(-1) with the increasing in monomer conversion from 11% to 85%, and the PDI maintained around 1.36. The living features of polymerizations with the PC1 and PC2 as catalysts have also been further supported by chain extension and synthesis of PMMA-b-PBnMA diblock copolymer. As a result, the simplicity and efficiency of benzaldehyde derivatives catalyzed PET-RAFT polymerization have been demonstrated under mild conditions. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 229-236