High-strength, programmable energy-dissipating liquid crystal elastomers via hydrogen-bond-locked 4D printing

Soft elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications. However, its application has been limited by its low strength and restricted structural tunability. Here, we report a 4D-printing strategy for programmable damping in which the 2-ureido-4[1H]-pyrimidinone (UPy) motif is grafted into the LCE network. The resulting quadruple hydrogen bonds (HBs) rapidly lock the alignment during direct ink writing (DIW), which is subsequently fixed by UV curing. The UPy-LCEs achieved impact energy-dissipation ratios of up to 89.24% and showed anisotropic hysteresis under cyclic compression, with R ≈ 53.8% parallel to the director and R ≈ 28.8% perpendicular to it; the energy-dissipation behavior can be tuned by printing parameters. The materials exhibit tensile strengths up to 9.4 MPa. By coupling HB alignment locking with 4D-printable architectures, this work establishes an integrated route to high-performance and geometry-programmable energy-absorbing LCEs for soft protection, damping, and robotic interfaces.