Regulation of Molecular Solar Thermal Energy Storage Capacity of Azobenzene and Acrylic Ester Copolymers through Hydrogen Bonding and Application in Solar Thermal Cells

Azobenzene photoactive molecules are capable of undergoing reversible E-to-Z isomerization upon excitation with light of specific wavelengths, allowing for stable storage and controllable release of photochemical energy. This makes them an effective approach for harnessing solar energy. Azobenzene polymers, in particular, show great potential for molecular solar thermal energy storage systems (MOST) owing to their excellent film-forming performance on various substrates. Herein, two types of ether-based azobenzene homopolymers and copolymers with acrylates tethered to different alkoxy side chain lengths are synthesized. By manipulating hydrogen bond networks constructed through the multiple ether bonds located in the azobenzene side chains and the 2-hydroxyethyl methacrylate (HEMA) units in the polymer, the photochemical energy storage capacity of the azobenzene polymers was effectively regulated. Additionally, a solar thermal cell was fabricated by employing the synthesized azobenzene copolymer, demonstrating stable charging-discharging cycles with promising scalability, highlighting potential applications in photothermal energy storage and controlled thermal release.