Thermodynamic and metastable colorimetric states of polydiacetylenes composite films and their applications for deciphering secret codes and sensing temperature

Electrospun polydiacetylenes (PDAs) composite materials are favorable for practical applications. However, a further understanding of the colorimetric changes of the composite systems in terms of thermodynamic and metastable states resulting from the interactions among multiple components is normally neglected. Herein, we functionalized diacetylenes with a variety of head groups and used them to prepare electrospun films with polyethylene oxide (PEO) as the matrix. Detailed investigations have been performed on the thermochromic properties of the PDA/PEO composite films to profile their general energy landscapes that describe the identified metastable and thermodynamic colorimetric states. Underlying mechanisms for the generation of multiple energy minima were proposed on the basis of chemical structures of PDA head groups. Utilizing the fined-tuned chromic responsiveness of the PDA/PEO composite films under thermo- and pH stimulations, as well as the features of thermodynamic and metastable states, we fabricated delicate devices for secret codes with multiple deciphering pathways and temperature sensors with a high-temperature recording function.