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 chi((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 chi((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.