PVK-based polymers with a high density of chromophores and improved processibility: synthesis and second-order nonlinearity optical properties

Five new poly(N-vinylcarbazole) (PVK)-based polymers, containing high density of second-order nonlinear optical (NLO) chromophores, are synthesized and described. Specifically, PVK is partially formylated by the standard Vilsmeier reaction, and the formyl groups of high reactivity are condensed with cyanoacetylated chromophores to afford PVK-based polymers in almost complete conversion. Their structures have been verified by ¹H-NMR, IR, and UV-Vis spectra. TGA results show that the modified polymers are thermally stable up to around 290 °C. The values of the NLO coefficient d₃₃ of these polymers, measured by in situ second harmonic generation, are 22.3, 20.9, 15.7, 5.6 and 11.5 pm/V, respectively.