Research Projects

Molecular photoswitches have garnered attention for over 30 years and have been investigated as energy storage systems in recent years. In these systems, photoswitchable molecules can act as “molecular batteries” storing (charging) and releasing (discharging) energy on demand by converting between its stable- and metastable-isomers upon absorption of light. However, the current challenge is that many of the photoswitches resist change to undergo photoisomerization in the solid/crystalline state owing to strong intermolecular interactions. Therefore, most of the isomerization studies have been performed either in solution state or in molten state to quantify their energy storage capabilities. In molten state (i.e. at higher temperatures), the thermal back isomerization processes competes with the forward one, making the energy storage and its quantification difficult. To solve this issue, molecular photoswitches need to integrate with some phase change materials (PCMs) that not only make possible the isomerization in the condensed state but also can undergo phase change upon isomerization, where both isomerization and latent heat energy will contribute to total energy storage. This proposal fills the gap by integrating liquid crystals (LCs) as PCMs with molecular photoswitches for energy storage applications. Specifically, our proposal focused on the development of indigo-based LC photoswitches, which remain largely untapped. Indigoid-based photoswitches: thioindigo, hemi-indigo and hemi-thioindigo are known to absorb in the visible region; therefore, by employing this class of photoswitches and integrating them with the LCs as PCMs allow us to absorb the maximum fraction of solar energy. Additionally, these derivatives exhibit robust photochromic behaviour, high fatigue resistance, and excellent thermal stability, qualities crucial for long-term photoswitching applications. These derivatives will be achieved by using two strategies: one by careful structural engineering, such as varying alkyl chain lengths, incorporating lateral substituents, or introducing π-conjugated spacers, which can lead to stable mesophases (nematic, smectic, or columnar) and reversible light-induced trans-cis or Z–E isomerization. Another strategy is to dope the Indigoid photoswitches into the commercially available LCs. The research methodology includes a modular organic synthesis of indigo derivatives, followed by extensive characterization and photoisomerization kinetics. The proposal is driven by the integration of recent advances in molecular photoswitches and soft matter science, aiming to systematically develop indigoid-based LC photoswitches as next-generation photothermal PCMs. By addressing a critical research gap, the study seeks to establish fundamental design principles for dual-functional, solar-responsive soft materials with potential applications in sustainable energy technologies.