Construction of Tunable Degradable Polydicyclopentadiene: Regulating the Performance–Environment Trade-off through Phosphoester Bonds

As a thermoset, polydicyclopentadiene (PDCPD) exhibits excellent mechanical properties and dielectric performance. However, its nondegradable carbon–carbon network poses significant environmental challenges. To address the inherent trade-off between polymeric material performance and environmental sustainability, this work introduces an approach by incorporating cleavable phosphoester bonds into PDCPD through ring-opening metathesis copolymerization of dicyclopentadiene (DCPD) with a cyclic phosphoester (CPE) as a comonomer. Guided by a reverse gel-point model based on the Miller–Macosko and Flory–Stockmayer theories, the optimal comonomer content was determined to achieve network degradability without compromising other key performances. The resulting polymeric materials exhibited tunable glass transition temperatures, tensile strength, and modulus, as well as good dielectric properties. Notably, the PDCPD formulation containing 14% CPE, prepared according to the model-predicted optimum, degraded completely within 12 h in a tetrahydrofuran solution of sodium methoxide while retaining good performance. This work provides a promising approach for designing high-performance thermosets with controllable end-of-life degradability, thereby expanding the potential applications of PDCPD.