The detection of mechanical stress in polymeric materials through optical variations has attracted considerable interest over the past ten years. In this tutorial review, the current state of knowledge concerning the preparation of polymers with mechanochromic features is summarized. Two types of procedures are illustrated and thoroughly discussed along with their respective structure–property relationships: the first resides in the physical dispersion of the dye in the form of supramolecular aggregates in a preformed polymer matrix; the second involves the covalent insertion of chromophoric units into the macromolecule backbone or side chains. Herein we review the simplicity of the preparative routes available, and their influence over the properties of the resulting dye–polymer systems, by focussing on the most illustrative examples described in the literature. Special reference is made to stimuli-responsiveness as a mechanical means towards innovative smart and intelligent materials.

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Mechanochromic polymer blends, i.e.polymer blends characterised by optical responsiveness to mechanical stimuli, have evoked major interest and experienced significant progress in recent years. Various examples are reported of chromogenic materials composed of a functional dye covalently linked to the polymer chains or physically dispersed in the continuous macromolecular matrix, the latter appears to be a more sustainable route for the industrial scale-up of these materials. This feature article examines the properties and performances of various mechanochromic materials prepared by using different thermoplastic polymers with non-covalently incorporated aggregachromic dyes. More specifically, the general mechanism underlying the optical phenomenon is introduced and the different approaches used to obtain chromogenic materials are presented and discussed considering both dye features and polymer characteristics. The combination of the properties of the blend components can often result in drastic differences in the material chromogenic responsiveness. The article concludes commenting and discussing the application of these kind of polymer devices as a new type of advanced materials and the perspective thereof.

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 (λ_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 °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.

In this review we describe several examples concerning the attractive properties of smart polymer composites containing aggregachromic dyes of different nature and structure. The dye–polymer interphase interactions depend on the equilibrium between the aggregated and the isolated forms of chromophores dispersed within the polymer matrix. Such interactions are easily perturbed by external solicitations like mechanical or thermal stresses, which induce a clear and rapid change in the composite’s optical properties both in absorption and in emission. These new stimuli-responsive composite materials therefore appear promising for the development of smart and intelligent polymer devices for sensing and safety applications.