Development of Diketopyrrolopyrrole-Based Smart Inks by Substituting Ionic Pendants and Engineering Molecular Packing Structures.

A series of diketopyrrolopyrrole (DPP) luminogen amphiphiles were newly designed and synthesized by a single-step anionic exchange reaction for controlling the photoluminescence properties in both solution and solid states. Multicolor emission in response to thermal, mechanical, and chemical stimuli was successfully demonstrated by engineering well-defined supramolecular assemblies. Phase transformation from the metastable amorphous solid to the stable orthorhombic crystal of [DP-Im][Br] provided the reversibly patternable light emission. Self-organization into the smectic crystalline phase of [DP-Im][TFSI] allowed us to show the linearly polarized light emission. By simultaneously applying [DP-Im][Br] and [DP-Im][TFSI], we demonstrated the fabrication of smart sensors for packaging of food or vaccines that can detect thermal attacks.