Acetone/Water as a new photoinitiating system for photografting: A theoretical study

Acetone can function as a high efficient photoinitiator for photografting copolymerization when it is mixed with water. The initiation mechanism of acetone/water as a new photoinitiating system for photografting copolymerization has been theoretically investigated at the B3LYP/6-31G** level. Acetone exists in the form of hydrates in its aqueous solution. Acetone dihydrate CH3COCH3·2H2O is readily excited to a triplet state (T1) under UV irradiation (254 nm) and then generates a radical C3H8O2 involving two single electrons. The photolysis of C3H8O2 is difficult to occur. However, the hydrogen abstraction from a polymer substrate by the ketonic oxygen of the radical is easier to take place, due to its lower energy requirement. The latter path produces a macromolecular radical that can initiate a photografting reaction easily. The photochemical reactions of acetone dihydrate produce less free radicals, leading to less termination reactions of the growing grafted chains. This study elucidates the photoinitiation mechanism of acetone/water photoinitiating system reasonably.