Atom Transfer Radical Polymerization and Third‐Order Nonlinear Optical Properties of New Azobenzene‐Containing Side‐Chain Polymers

The atom transfer radical polymerization (ATRP) technique has been successfully applied to synthesize a series of nonlinear optically (NLO) active homopolymers, 4‐(4‐nitrophenyl‐diazenyl) phenyl acrylate ( P ‐ NPAPA ) and 4‐(4‐methoxyphenyl‐diazenyl) phenyl acrylate ( P ‐ MPAPA ), containing azobenzene groups on the side chain. The third‐order NLO properties of the polymer films were measured by the degenerated four‐wave mixing (DFWM) technique. A dependence of the χ (3) values and response times of polymers on their number‐average molecular weight and the electronic effect of the substituent (nitro‐ or methoxy‐) on the azobenzene group have been evidenced. The increasing χ (3) value of the polymer films at the magnitude of about 10 −10 was displayed with increasing molecular weight and the presence of the push‐pull electronic system contributes much in enhancing the third‐order NLO susceptibility of polymers.