Photoreactions offer precise control over reaction kinetics and material properties; however, reproducibility is often limited by poorly characterized or inaccessible photoreactor setups. We report a low‐cost, modular light‐emitting diode (LED)‐based photoreactor designed for small‐scale photochemical reactions, featuring precise control over light intensity, wavelength, and temperature. Interchangeable 365 and 395 nm LED arrays, controlled via a variable DC power supply, enable tunable and reproducible ultraviolet (UV) exposure. A custom‐built UV sensor and thermistor provide quantitative determination of the irradiance and real‐time monitoring of the internal reaction temperature. Irradiance mapping confirmed spatial uniformity and voltage‐dependent control of the light intensity. As proof of concept, the built photoreactor was applied to a photoinitiated polymerization‐induced self‐assembly reaction, using a polyethylene glycol‐based macro‐chain transfer agent, 2‐hydroxypropyl methacrylate monomer, and a photoinitiator. Results demonstrate that both temperature and light intensity significantly influence the morphology of the resulting nanoparticles, with larger vesicular structures forming only when the system is preheated before light exposure. This highlights the importance of reporting and controlling reaction conditions such as temperature, light intensity, and thermal equilibration. The presented modular photoreactor bridges a gap in literature, providing a reproducible and accessible tool for photopolymerization and broader photochemical applications.
Vermeijlen et al. (Mon,) studied this question.