The detection of 2,4-dinitrotoluene (DNT) by fluorescence quenching of a new class of polyimines consisting in pi-conjugated segments regularly alternated with chiral C-2 symmetry units has been studied for solutions and thin films. Their photophysical properties and their sensitivity towards DNT detection has been compared to those of a small model molecule incorporating the same pi-conjugated segment. In solution, all the compounds exhibit the same photo-physical properties and sensitivity towards DNT detection. In contrast, for thin films, better performances are observed in static conditions for this new class of polyimines compared to the small model molecule. It seems that C-2 symmetry units prevent from the stacking of the pi-conjugated segments and provide in addition to high fluorescence signal an improved diffusion of the analyte inside the films. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4141-4149, 2009