Toughening anti-overswelling semicrystalline polymer hydrogels with ultra-small hydrophobic nanoparticles

Semicrystalline polymer hydrogels (SC-gels) are intrinsically electrolyte tolerant and over-swelling resistant, emerging as promising candidates for applications in solution environments. However, SC-gels with high mechanical strength are usually brittle. In the present work, by introducing ultra-small hydrophobic nanoparticles, highly-stretchable SC-gels (15 times of its original length) with fracture energy as high as 16.3 MJ M-3 (similar to 8 times of the control) were obtained, without compromising neither the stiffness nor the intrinsic virtues of conventional SC-gels, such as electrolyte tolerance, over-swelling resistance and thermal-modulated ultra-fast recovery. The newly formed crosslinks between these hydrophobic nanoparticles and crystallites in SC-gels are found to be the key for such improvement in toughness; while the chemistry of the nanoparticles themselves are less determining. Therefore, different ultra-small hydrophobic nanoparticles can be incorporated into these tough SC-gels, provided their surface capping agents are similar.