Photoinduced Metal-Free Atom Transfer Radical Polymerization Using Highly Conjugated Thienothiophene Derivatives

Photoinduced metal-free atom transfer radical polymerization (ATRP) activated by highly conjugated electron-rich thienothiophene derivatives, namely 4-[2-(4-diphenylaminophenyl)-thieno[3,2- b ]thiophen-3-yl]benzonitrile (TT-TPA), 4-[2,5-bis(4-diphenylaminophenyl)-thieno[3,2- b ]thiophen-3-yl]benzonitrile (TPA-TT-TPA), 4-(2-(4-(1,2,2-triphenylvinyl)phenyl) thieno[3,2- b ]thiophen-3-yl)benzonitrile (TT-TPE) and 4-(2,5-bis(4-(1,2,2-triphenylvinyl)phenyl)thieno[3,2- b ]thiophen-3- yl)benzonitrile (TPE-TT-TPE) is reported. Polymerization of methyl methacrylate (MMA) is efficiently activated and deactivated with light, forming polymers with controlled the molecular weight characteristics, dispersity, and chain end functionality. Polymerization studies and DFT calculations revealed that TT-TPA is the most efficient activator due to the favorable thermodynamic properties.