Synthesis and characterizations of highly fluorinated poly(arylene ether)s for quadratic nonlinear optics

New highly fluorinated poly(arylene ether sulfone)s (FPAES), poly(arylene ether ketone)s (FPAEK), and poly(arylene ether)s with several types of NLO chromophores as pendant groups were obtained by a polycondensation reaction using very mild conditions. The different polymer structures were designed with the objective to investigate the influence of both the polarity of the chromophore and the nature of the tether between the NLO chromophore and the chain. The resulting copolymers have glass transition temperatures (Tg\u2019s) varying between 160 and 215\ub0C, and they are stable up to 280\ub0C under nitrogen. Although these copolymers are soluble in common organic solvents, cyclohexanone gave the best film quality and was used for the film preparation. After optimization of the poling conditions, the in situ second harmonic generation (SHG) measurements gave nonresonant values of the second-order susceptibilities d33 ranging from 2 to 8 pm/V, and the SHG signals of the poled polymer films were found to be thermally stable below 130\ub0C. Although being comparable with the values obtained for similar polymers and chromophores in the literature, d\u2083\u2083 are smaller than those obtained for more conventional NLO polymers like PMMA-Disperse Red One (PMMA-DR1), which was taken as a reference. An unusual drop of the SHG signal during cooling was found in the thermally assisted orientation process. This drop occurred at a characteristic temperature below Tg. In this relaxation process which has never been observed, intra- and interchain dipolar interactions are shown to play an important role, which is amplified in the case of chromophores which have their donor group embedded in the main chain, connected by two rigid tethers.Peer reviewed: YesNRC publication: Ye