Synthesis and non‐linear optical characteristics of crosslinked and linear epoxy polymers with pendant tolane chromophores

Linear and crosslinked epoxy polymers containing high concentrations (ca. 86 wt.‐%) of pendant 4‐(4‐nitrophenylethynyl)aniline [4‐amino‐4′‐nitrotolane] chromophores were synthesized. They exhibit a smectic phase in the bulk once heated above the glass transition temperature (ca. 70°C). The appearance of the highly scattering smectic phase could be avoided by starting the crosslinking process of thin polymer films in the presence of solvent. Application of corona poling during crosslinking resulted in a highly polar polymer, exhibiting a very large birefringence of ca. 0,17 at 633 nm. Moreover, the birefringence remained stable during annealing at 80–90°C for ca. 30 days. The electro‐optic coefficient, determined from the Pockels‐effect, was roughly 8 pm/V for r113 at 633 nm.