A new L-PLA@Croconaine-based all organic composite: selective management of thermophysical properties of L-PLA by a photothermal croconaine-based molecular additive

• A new all-organic composite material L-PLA@CR-BI was developed by incorporating a benzoindolenine-based croconaine (CR-BI) into L-PLA matrix. • CR-BI acts as a photothermal molecular additive with high affinity for the PLA, forming a homogeneous molecular network inner L-PLA. • With just 1% CR-BI we are able to selectively modulate the thermal properties of PLA, with an impressive increase of more than three times of thermal diffusivity and conductivity, while preserving electrical insulation. • The very low concentration of CR-BI additive allows to preserve the thermal stability of PLA. • CR-BI molecules into PLA matrix increases the polymer chain mobility, facilitating the release of thermal energy thank to the formation of newly ordered structures, making this composite material interesting also for energy storage applications. Selective management of chemico-physical properties of l -polylactic acid (L-PLA) is pivotal to broaden the application range of this polymer. As a thermally and electrically insulating polymer, its application in energy field and electronic instruments requires innovative strategies capable of selectively tune thermal and electrical properties, safeguarding mechanical properties and thermal stability. Here, we propose a molecular approach to selectively enhance thermal conductivity of l -PLA, preserving electrical insulating capacity, by incorporating a benzoindolenine-based croconaine (CR-BI) as functional photothermal additive. l -PLA@CR-BI composite solid layers were prepared via solution casting, by combining different amounts of CR-BI and comprehensively characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), UV–vis and FTIR spectroscopy, electrical, photothermal and thermophysical measurements. l -PLA@CR-BI composites displayed homogeneous coloration and a uniform CR-BI molecular dispersion inner l -PLA, with a molecular-level thermal network resulting in a strong impact on its thermal properties. Remarkably, the inclusion of only 1wt% CR-BI led to an over threefold increase in thermal diffusivity and conductivity compared to neat l -PLA. TGA evidenced a CR-BI-induced enhancement of polymer chain mobility and the formation of new crystalline domains, improving heat transfer and suggesting thermal energy storage applications. Importantly, the electrical insulating nature of l -PLA remained unchanged across all compositions. To the best of our knowledge, this work provides the first demonstration of croconaines as molecular modulators of l -PLA’s chemico-physical properties, enabling selective and efficient enhancement of thermal transport while maintaining electrical insulation- an advance with significant implications for sustainable polymer-based electronic and energy materials.