Tuning Stiffness and Backbone Rigidity of Diels–Alder-Based Thermosets with Macrocyclic Telechelic Cyclopentadiene Monomers

Dynamic covalent polymer networks based on Diels–Alder (DA) chemistry provide a versatile platform for reprocessable and recyclable thermosets. While mechanical properties in these systems are typically tuned through cross-link density or chemical composition, the role of segmental mobility within network junctions has received far less attention. Here, we present a cyclopentadiene–maleimide (Cp–Mal) thermoset platform that enables direct control over segmental mobility through molecular topology. Telechelic cyclopentadiene monomers featuring either macrocyclic or acyclic backbones with nearly identical chemical reactivity were synthesized and combined to form dynamic thermoset networks with constant stoichiometry. A systematic increase in cyclic monomers is consistent with progressive restriction of segmental motion, producing a continuous transition from moderately soft to extremely stiff, glassy thermosets. These results demonstrate that backbone topology and segmental mobility serve as powerful, orthogonal design parameters for controlling thermomechanical performance of dynamic polymer networks without altering network chemistry.