Bis(benzoxazolyl)stilbene excimers as temperature and deformation sensors for biodegradable poly(1,4-butylene succinate) films

In this work, new and innovative polymeric film sensors based on excimer luminescence and responsive to both mechanical and temperature stress were obtained through the dispersion of moderate amounts (0.02 - 0.2 wt%) of the food-grade dye bis( benzoxazolyl) stilbene (BBS) into a thermoplastic aliphatic biodegradable polyester [ poly( 1,4-butylene succinate), PBS]. Emission from BBS excimers emerged with dye concentrations higher than 0.05 wt% conferring to the film a green luminescence (lambda(exc). = 366 nm). On applying mechanical stress at rt, the PBS reorganization efficiently breaks the BBS arrangements leading to the prevalence of blue emission from the excited isolated chromophores. Moreover, the optical behaviour of PBS - BBS quenched blends was thermally affected in the range 50 - 80 degrees C, providing composite films characterized by a very sensitive temperature dependent luminescence response. The easy modulation of the luminescent properties of polyester films by varying the supramolecular organization of BBS dispersed molecules by thermal or mechanical perturbations suggests various applications in the field of smart and intelligent films from thermoplastic materials.