Highly efficient, thermally stable and optically transparent third-order nonlinear optical copolymers consisting of fluorene and quinoxaline/quinoline units

New fluorene-linked conjugated polyquinoxaline and polyquinoline possess adequate optical transparency, excellent thermal stability and good processability. Degenerate four-wave-mixing measurements on these polymers yield nonresonant third-order susceptibilities as high as 1.1x10(-10) esu and nonresonant second-order hyperpolarizabilities per repeated unit as high as 2.0x10(-31) esu. The large nonlinearity originates from the high electron delocalization due to the planar rigid structure of the fluorene ring and the imine nitrogen of quinoxaline and quinoline.