High glass transition chromophore functionalised polyimides for second-order nonlinear optical applications

Nonlinear optical (NLO) polymers with glass temperatures (Tg) as high as 291°C were prepared, PI 2-4 by covalent bonding of a chromophore to the backbone of hydroxyl polyimides via a Mitsunobu reaction, PI 1 as a donor-embedded polyimide was synthesised by polycondensation of a diaminochromophore and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride in a two-step reaction. Poled films of the polymers were measured for their second-harmonic generation (SHG) effect and showed d33 values up to 20 pm/V. Some of the films show a stable nonlinear optical response even to 90% of remaining NLO-intensity at 125°C during 200 h.