Ultra‐High Molecular Weight Alpha‐Amino Poly(Methyl Methacrylate) with High Tg through Emulsion Polymerization by Using Transition Metal Cation–Tertiary Amine Pairs as a Mono‐Centered Initiator

As some complexes of transition metal cations in high oxidation state can oxidize tertiary amines under proper conditions into aminoalkyl radicals to initiate polymerization of electron‐deficient vinylic monomers, they form mono‐centered redox‐initiation pairs for preparation of 100% alpha‐amino telechelic polymer. Radical emulsion polymerization of methyl methacrylate (MMA) is performed by using water‐soluble amines as a reducing agent and Fe^III or Cu^II as an oxidizing agent. Tertiary amines such as 2‐(N,N‐dialkylamino)ethanol and N,N,N′,N′‐tertramethylethylenediamine exhibit a higher initiation activity. Monomer conversion can reach 80% in 8 h and 95% in 16 h, leading to PMMA with an absolute weight‐average molecular weight above 1.5 × 10⁶ g mol^?1. The alpha‐amino terminal functionality is verified by ultraviolet‐induced diarylketone‐initiated radical bock polymerization by using these PMMA chains as the macro‐sensitizer. Such a facile heterogeneous technique results in syndiotactic‐rich high‐T_g PMMA (rr > 50%, T_g = 124–127 °C). PMMA chains may be oxidized by Fe^II–O₂ complexes to initiate further radical polymerization, leading to PMMA with a long‐chain branched architecture.