Controlled Functionalization of Crystalline Polystyrenes via Activation of Aromatic C−H Bonds

The iridium-catalyzed functionalization of the C−H bond of commercial polystyrenes with three types of tacticities (syndiotactic, isotactic, atactic) using boron reagents is reported. The boronate ester group in the polystyrene was further converted to hydroxy and arene via oxidation and Suzuki−Miyaura cross-coupling, respectively. These functionalizations proceeded without affecting the tacticity or chain length of the starting polymer, and the functional group concentration was easily controlled by changing the ratio of boron reagent to polymer repeating unit. The size and concentration of the functional group in the syndiotactic polystyrenes were found to have huge impacts on the thermal properties of the functionalized polymers. The incorporation of even a small amount (