The supporting information for the article "Regulation of Hard Segment Cluster Structures for High-performance Poly(urethane-urea) Elastomers" provides detailed experimental procedures, characterization methods, and supplementary data. The study focuses on the synthesis and characterization of poly(urethane-urea) elastomers with different hard segment structures (PCL-AD and PCL-DD) to enhance their mechanical properties and recyclability. **Materials:** The materials used include N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dibutyltin dilaurate (DBTDL), hexamethylene diisocyanate (HDI), adipic dihydrazide (AD), and dodecanedioic dihydrazide (DD). Polycaprolactone diol (PCL diol) was also used as a starting material. **Fabrication of the Elastomer:** The PCL diol was melted and reacted with HDI and DBTDL in DMAc under an N2 atmosphere. Chain extenders (AD or DD) were then added to form the final elastomer solution, which was cast and dried to obtain the elastomer. **Characterization:** - **General Characterization:** Techniques used include ATR-FTIR, ¹H-NMR, ¹³C-NMR, DSC, WAXD, TGA, DMA, and SEM/TEM to analyze the chemical composition, thermal properties, microstructure, and mechanical properties of the elastomers. - **Tensile Tests:** Mechanical properties were evaluated using a universal tensile machine, including tensile strength, toughness, true stress, true strain, cyclic tensile testing, and fracture energy calculations. - ** Recycling and Degradation Tests:** Recycling was achieved by re-dissolving and drying the elastomer fragments. Degradation was tested using lipase in PBS buffer, with mass reduction rates measured over time. **Simulation and Calculation:** - **All-atom Molecular Dynamics Simulations:** Simulations were performed using Materials Studio to optimize the structure and dynamics of the elastomers, focusing on hydrogen bonding and cohesive energy density. - **Density Functional Theory (DFT) Calculations:** DFT calculations were conducted to optimize the geometry and binding energy of the hard segments, correcting for basis set superposition error (BSSE). Supplementary figures and tables provide additional data on FTIR spectra, NMR spectra, temperature dependence of modulus, TGA curves, TEM images, WAXD results, cyclic tensile curves, SEM images, and degradation processes.The supporting information for the article "Regulation of Hard Segment Cluster Structures for High-performance Poly(urethane-urea) Elastomers" provides detailed experimental procedures, characterization methods, and supplementary data. The study focuses on the synthesis and characterization of poly(urethane-urea) elastomers with different hard segment structures (PCL-AD and PCL-DD) to enhance their mechanical properties and recyclability. **Materials:** The materials used include N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dibutyltin dilaurate (DBTDL), hexamethylene diisocyanate (HDI), adipic dihydrazide (AD), and dodecanedioic dihydrazide (DD). Polycaprolactone diol (PCL diol) was also used as a starting material. **Fabrication of the Elastomer:** The PCL diol was melted and reacted with HDI and DBTDL in DMAc under an N2 atmosphere. Chain extenders (AD or DD) were then added to form the final elastomer solution, which was cast and dried to obtain the elastomer. **Characterization:** - **General Characterization:** Techniques used include ATR-FTIR, ¹H-NMR, ¹³C-NMR, DSC, WAXD, TGA, DMA, and SEM/TEM to analyze the chemical composition, thermal properties, microstructure, and mechanical properties of the elastomers. - **Tensile Tests:** Mechanical properties were evaluated using a universal tensile machine, including tensile strength, toughness, true stress, true strain, cyclic tensile testing, and fracture energy calculations. - ** Recycling and Degradation Tests:** Recycling was achieved by re-dissolving and drying the elastomer fragments. Degradation was tested using lipase in PBS buffer, with mass reduction rates measured over time. **Simulation and Calculation:** - **All-atom Molecular Dynamics Simulations:** Simulations were performed using Materials Studio to optimize the structure and dynamics of the elastomers, focusing on hydrogen bonding and cohesive energy density. - **Density Functional Theory (DFT) Calculations:** DFT calculations were conducted to optimize the geometry and binding energy of the hard segments, correcting for basis set superposition error (BSSE). Supplementary figures and tables provide additional data on FTIR spectra, NMR spectra, temperature dependence of modulus, TGA curves, TEM images, WAXD results, cyclic tensile curves, SEM images, and degradation processes.