Dynamic Linear Polymers via [2π + 2π] Cycloaddition Reactions Using Dicoumarin Monomers

Dynamic polymers represent a versatile class of materials that reversibly change their structure and properties in response to external stimuli. These materials offer unique functionalities for applications in sensors, actuators, coatings, and recyclable systems. Topochemical polymerization, a solid‐state reaction governed by molecular alignment within a crystal lattice, enables regio‐ and stereo‐selective formation of polymers. However, few examples of dynamic linear polymers exist, and coumarin derivatives have not yet been explored under topochemical conditions. In this study, a series of n ‐alkyl bis‐coumarin monomers is synthesized and investigated for their ability to undergo reversible [2π + 2π] cycloaddition. Monomers with butyl and hexyl spacers form photoactive crystals capable of reversible polymerization and depolymerization under 365 nm and 254 nm irradiation, respectively, while the octyl analogue remains inactive due to excessive olefinic spacing. Structural analysis reveals that crystal packing and solvent‐dependent recrystallization critically influence photoreactivity.