Soluble side-chain polyimides bearing Disperse Red One groups (PI-DR1) have been synthesized and characterised for second order nonlinear optics (second order NLO). Thermally oriented samples show a very good orientational stability. In order to overcome the degradation of DR1 inherent to the orientation process which is performed at 210 degreesC, photoassisted poling was carried out and the second harmonic generation signal measured during the poling. The degradation ratio decreases to less than 2 %, with this method, but there is also a decrease in the orientational stability compared with thermally assisted poling. However, by carrying out photoassisted poling at different temperatures varying from 20 to 150 degreesC, it has been shown that the second order susceptibility d(33) increases, the degradation ratio keeps a low value, and the orientational stability increases and becomes comparable with the one observed for thermally poled samples provided the poling temperature is higher than 120 degreesC. This last temperature has been identified in a previous work as a secondary glass transition temperature for this polyimide.