mechanochromic lldpe filmsNew article just published by the Smart Polymer Group: "Mechanochromic LLDPE Films Doped with NIR Reflective Paliogen Black" (C. Micheletti, P. Minei, Prof. G. Ruggeri, Prof. A. Pucci). The work shows the self-diagnostic properties of P-black/LLDPE film as a new solution to detect deformations through optical and thermal outputs.
Here the abstract of the article.
The perylene bisimide derivative Paliogen Black (P-black) is proposed as a new chromogenic probe that shows visible (Vis) and near-infrared (NIR) responses after mechanical solicitations of host linear low-density polyethylene (LLDPE) films.

P-black is reported to display strong absorption in the vis spectrum and unusual reflective and cooling features in the NIR region. Uniaxial deformation of the 2.5, 5, and 10 wt% P-black/LLDPE films yields a dichroic absorption under polarized light with color variations attributed by the computational analysis to the distinct anisotropic behavior of the transition dipole moments of P-black chromophores. When LLDPE films are deformed, P-black aggregates reduce their size from ≈30–40 µm to ≈5–10 µm that, in turn, causes reflectivity losses of about 30–40% at the maximum elongation. This gives rise to warming of 5–6 °C of the locally oriented film placed in contact with a black substrate under the illumination with an IR lamp for 5 s. These features combined with the high sensitivity of the Vis-NIR response toward mechanical solicitations render P-black as a new solution to detect uniaxial deformations of plastic films through both optical and thermal outputs.
Their work is available at the following link: https://doi.org/10.1002/marc.202000426