Direct pyrolysis mass spectrometry technique was applied to investigate the characteristics of polylactide, (PLA) nanofibers containing organically modified montmorillonites, Cloisite 15A, (C15A) Cloisite 20A, (C20A) and Cloisite 30B, (GOB) prepared by electrospinning. As the amount of Cloisite present in the composites was increased, the fiber diameters became slightly narrower compared to neat PLA fiber due to the presence of quaternary ammonium salt as organic modifier increasing electrical conductivity. The diameters of the fibers were smallest for PLA/C15A composite and largest for PLA/C30B composite. This behavior was directly related to the amount of organic modifier present in the nanoclays. Significant increase in the thermal stability of PLA composite nanofibers was detected compared to not only neat PLA and PLA fiber but also compared to PLA/organoclay composites and associated with the increase in extent of delamination evidenced by pyrolysis mass spectrometry results. (C) 2017 Elsevier B.V. All rights reserved.