This study investigates the tensile (compressive) behavior of a single molecular chain of the rod-like polyimide poly-(P-phenylene pyromellitimide) (PMDA-PDA) at zero temperature using a density functional theory (DFT) calculation. The force-displacement curve of the single PMDA-PDA molecular chain is calculated from simulations of predefined strain deformations along the axis of the molecular chain, allowing a discussion of the distribution and change of local strain of the molecular chain. We find that the six-membered ring of the PDA group deforms the most until an engineering strain of 7.0% under uniaxial tensile develops. However, eventually carbon-nitrogen bonds between the PMDA and PDA groups break at the point where fracture of the molecular chain occurs. (C) 2004 Elsevier Ltd. All rights reserved.