Photocycloaddition as a Tool for Modulation of the Lower Critical Solution Temperature in a Molecular π‐System to Control Transmission of Solar Radiation
Satyajit Das, Dipak Patra, Sreejith Shankar, Ayyappanpillai Ajayaghosh
Abstract
Abstract Diels–Alder photocycloaddition, a well‐known textbook reaction, has not been explored in materials chemistry. Herein we describe how this classical photochemistry can be used to modulate the lower critical solution temperature (LCST) of a molecular π‐system, which can further be exploited for the controlled transmission of solar radiation for the management of indoor heat and light. An amphiphilic anthracene derivative 9‐PA‐1 exhibited LCST behavior at 27–32 °C with a reversible transition from a transparent to an opaque phase in water (1–5 mM). Irradiation of a toluene solution of 9‐PA‐1 with 365 nm light resulted in a [4+2] photocycloadduct 9‐PA‐2 , which exhibited a modulated LCST behavior at 25–27 °C, at a concentration as low as 6 μM. The photocycloaddition of 9‐PA‐1 was significantly retarded in water, making it a stable candidate for the design of sustainable smart windows. We also demonstrated 100 cm 2 smart window prototypes (Δ T lum 82 %, Δ T IR 68 %, ΔT sol 73 %) with more than 1000 cycles of stable operation.