The real-time mechano-optical behavior of Polyimide 3,30,4,40-benzophenone tetracarboxylic dianhydride (BTDA) 1,6-diaminohexane (DAH) [PI(BTDA-DAH)] films during uniaxial deformation was investigated in the glassy and rubbery states as a function of temperature and stretch rate to understand the stretching characteristics of the polymer and elucidate the structural evolution. The study combined real-time spectral birefringence with true stress and true strain measurements and the data were further augmented by offline DSC and WAXD measurements. During deformation near glass transition temperature, initial photoelastic regime exhibiting very small slope is followed by regimes II and III. As the deformation temperature increases, the initial photoelastic regime disappears and gives way to temperature-independent regime I following classic stress-optical behavior. Regime I is followed by either a negative deviation from SOR into regime IIIa at lower deformation temperatures, or a positive deviation from SOR into regime II at higher deformation temperatures which eventually transitions into regime IIIc at large strains. The polymer was essentially amorphous in regime I. As the deformation increased, strain-induced crystallization occurred in regime II where crystallinity as high as 24% was achieved. The strain-induced crystals enhanced network connectivity and increased the rate of polymer chain orientation before transitioning to regime IIIc. Under conditions where regime II was not observed, a linear mechano-optical response in regime I extended to higher deformations before transitioning into regime IIIa where the highly oriented chains exhibited a "nematic-like" order with translational disorder along the chain directions. Based on the above observations a schematic for the structural evolution of PI(BTDA-DAH) during uniaxial deformation was proposed. (C) 2017 Elsevier Ltd. All rights reserved.