Creep-Resistant Covalent Adaptable Heterogeneous Networks

Dynamic covalet networks, exemplified by Vitrimers, hold significant promise for sustainable polymers due to their reprocessability and mechanical robustness. However, their susceptibility to creep deformation under sustained stress, driven by dynamic bond mobility, limits practical utility. We report a multiphase Vitrimer elastomer based on transesterification. Two distinct carboxylic acid cross-linkers containing dynamic β-hydroxy ester bonds were highly cross-linked into epoxidized natural rubber (ENR). Dithiodibenzoic acid (DS) bearing benzene rings first undergoes preferential aggregation via π–π interactions and thermally cross-links with epoxy groups to form a rigid hard phase, thereby restricting chain slippage and rearrangement at service temperatures to enhance creep resistance. Concurrently, 3,3′-dithiodipropionic acid (DD) establishes a soft phase with epoxy groups in the matrix, while preserving the material’s reprocessability. Stress relaxation and creep tests reveal that the hard domains/regions within the heterogeneous network structure impede segmental relaxation at relatively low temperatures, thereby enhancing the material’s creep resistance. At elevated reprocessing temperatures, however, these hard domains maintain dynamic bond exchange and segmental mobility, while the soft phase facilitates material reprocessability. This work establishes a scalable design framework for Vitrimers that synergistically enhances creep resistance and recyclability, addressing critical demands for durable yet sustainable engineering materials.