Figure 3.
(a) Images of a 1-PU film show that the fluorescence is turned on upon deformation and switched off when the stress is removed. Top and bottom images were taken under irradiation with 365 nm light and ambient illumination, respectively. (b) Emission spectra of a pristine 1-PU film in the initial state and upon uniaxial deformation to the indicated strains. (c) Emission spectra of the sample used in (b) recorded upon gradually releasing the stress and thereby reducing the strain; the stress-free state had a residual elongation of 190%, due to hysteresis. All spectra were recorded with λex = 385 nm.