Semicrystalline Hydrophobically Associated Hydrogels with Integrated High Performances

Hydrophobically associated hydrogels (HA gels) are one of most extensively investigated high strength hydrogels. Semicrystalline HA gels, prepared by micellar copolymerization, show high strength and notable functionalities of self-healing and shape-memory. However, the hydrophobic comonomers in these semicrystalline HA gels are usually limited to the long alkyl length monomers (18-alkyl(meth)acrylates). In the present work, N-acryloyl 11-aminoundecanoic acid (A11AUA), consisting of 10 -CH₂ groups and a -COOH group at the end of alkyl chain, was used as hydrophobic comonomer to prepare physical A11AUA-based HA gels in the presence of high concentration cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate. Differential scanning calorimetry, wide-angle X-ray scattering, and small-angle X-ray scattering experiments had identified that the A11AUA-based HA gels possessed crystalline domains and clusters of crystalline domains, while lauryl methacrylate (C12M)-based HA gels were amorphous. As a result, A11AUA-based HA gels displayed much better tensile properties than those of C12M-based HA gels. At the optimal condition, the A11AUA-CTAB HA gel demonstrated integrated high performances, including high stiffness (E of 1016 kPa), high strength (σ_f of 0.75 MPa), high toughness (T of 7540 J/m²), rapid self-recovery (94% recovery after heat treatment at 60 °C for 2 min), outstanding shape memory (fully recovered to the permanent shape only 2-14 s), and excellent self-healing properties (as healed at 60 °C for 2 h; stress and strain healing efficiency reached to 64% and 85%, respectively). We believe this work provides a new insight for HA gels, which is beneficial to design new hydrogels with integrated high performances, such as high strength, high toughness, large extensibility, and shape-memory and self-healing properties.