Luminescence of Polyamide-6 α and γ forms (Invited)

We report the results of an experimental study of polymer bulk material Polyamide-6 luminescence properties. A new effect of persistent time-delayed luminescence was revealed at room temperature. Detailed inspection of the effect has shown strong dependence on the microscopic crystalline structure of the polymer. Two morphological forms were recognized with the aid of X-ray Bragg reflection treating. The afterglow with the decay time exceeding 10 seconds was found to appear at about 150 K for the γ-form and is observed at room temperature for the α- form. The temporal dependence of time-delayed luminescence was found to satisfy hyperbolic Becquerel law, thus indicating the recombination origin of the effect. Also, emission realized with the excitation by third optical harmonics of a femtosecond Ti:Sapphire laser (267 nm) at room temperature was examined. The registered luminescence spectra were found quite different for these forms. While γ-form samples exhibit spectrum at the visible region, the α-form emits a pronounced luminescence output in the near UV (340 nm).