Nonlinear optical (NLO) polymers with glass temperatures (T-g) as high as 291 degreesC 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 d(33) 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 degreesC during 200 h. (C) 2001 Elsevier Science Ltd. AU rights reserved.