Secret Ink: Kinetically Controlled Polymorphic Superstructure of Transparent Illuminant

Simultaneous manipulation of both transparency and luminescence is one of the biggest challenges in developing security materials and memory devices. To understand the crucial factors influencing such optical properties, we synthesized a new class of a transparent luminescent molecule (mPD) comprising dendritic alkyl chains as a model organic compound. As the result of the fundamental phase-transition behavior and the microscopic structure analysis, it was demonstrated that there are metastable and stable phases, determined by the competition between H-bonding and π–π interactions. Interestingly, the polymorphic superstructure of mPD was effectively manipulated by the kinetic control of molecular packing process, which causeda significant change in optical properties. Specifically, the visibility and luminescent intensity of mPD material can be precisely regulated by sample processing and external stimuli. Our investigation highlights that the manipulation of molecular packing structure of a luminescent molecule via kinetic control can be a useful strategy for developing optically tunable smart luminescent materials.