Concurrent Tandem Living Radical Polymerization: Gradient Copolymers via In Situ Monomer Transformation with Alcohols

We developed concurrent tandem living radical polymerization as a novel methodology to efficiently, conveniently, and in one-pot produce gradient copolymers via in situ monomer transformation. The key is to employ, a metal alkoxide [Al(Oi-Pr)(3), Ti(Oi-Pr)(4)] and an alcohol solvent (ROH) in ruthenium-catalyzed polymerization of conventional ester-based methyl (meth)acrylate [M(M)A], where the monomer was directly transformed into R(M)A via in situ transesterification to gradually vary the monomer composition during the copolymerization. Typically, methyl methacrylate (MMA) was polymerized with a ruthenium catalyst in the presence of excess ethanol (ROH) and Al(Oi-Pr)(3) cocatalyst to give well-controlled gradient copolymers from MMA to EMA along the polymer chain, in which the original MMA was gradually converted into ethyl methacrylate (EMA) by the cocatalyst. This concurrent tandem polymerization, in conjunction with a wide variety of alcohols, efficiently and conveniently produced various gradient copolymers including long alkyl chain and PEG pendent groups. The obtained copolymers further exhibited unique physical properties different from the corresponding random and block counterparts.