Synthesis and properties of a new second-order NLO chromophore containing the benzo[b]furan moiety for electro-optical materials

Abstract

To further explore the potential application of the benzo[b]furan ring in NLO chromophores, we have designed and synthesized a new chromophore (A) having a 1,1,7,7-tetramethyljulolidine fused furan ring as the electron donor group to systematically investigate the role of benzo[b]furan ring in NLO chromophores. Its corresponding chromophore B using 8-(1-hydroxyhexoxy)-1,1,7,7-tetramethyljulolidine as electron donor group was also prepared for comparison. Upon introducing benzo[b]furan ring at the donor end of chromophore A, a reduced energy gap of 1.14 eV was obtained compared with chromophore B (E_ge = 1.28 eV). Furthermore, the macroscopic EO activity of the new chromophores was investigated using guest-host doped polymer films (doping chromophores A or B into amorphous polycarbonate (APC) with a loading density of 20 wt%). The poled films containing chromophore A achieved a maximum EO coefficient (r₃₃) of 52 pm V⁻¹ at 1310 nm, which is larger than the poled films containing chromophore B (r₃₃ = 35 pm V⁻¹). These two chromophores showed excellent thermal stability with onset decomposition temperatures higher than 229 °C. The combined large EO activities and high thermal stability indicates the important role of the benzo[b]furan moiety in the construction of new NLO chromophores.