关键词: 丝素蛋白微-纳米纤维, 气凝胶, 硅烷改性, 超弹性, 吸油性能, 力学性能, 疏水性能

Abstract:

Objective Silk fibroin (SF) aerogels prepared by conventional regeneration-dissolution process generally suffer from poor mechanical elasticity, resulting in weak oil absorption performance of the hydrophobically modified SF aerogels. This research aims to prepare highly elastic SF-based aerogels with excellent oil absorption properties for practical applications by using SF micro-nanofibrils (SMNF) aerogels as carriers, following the hydrophobic modification.

Method The SMNF aerogels were fabricated by a freeze-induced assembly process using low-melting solvent liquid-phase exfoliated SMNF as precursors. Subsequently, the SMNF aerogel was hydrophobically modified by a methyltrimethoxysilane (MTMS) chemical vapor deposition strategy. The microstructure, element distribution and mechanical properties of MTMS modified SMNF (MS) aerogel were characterized by scanning electron microscopy, energy dispersive spectroscopy, infrared spectroscopy and universal material testing machine. Meanwhile, the oil absorbency of MS aerogel was systematically studied.

Results The urea/guanidine hydrochloride deep eutectic solvent liquid-phase exfoliated SMNF retained the micro-nanoscale fibril structures of natural silk fibers (Fig.1), facilitating the construction of highly elastic SF aerogels. The resulting MS aerogel was characterized by hierarchical cellular architectures (Fig. 2), which endowed it with low density (5.36 mg/cm³) and high porosity (99.63%). The MS aerogel exhibited high compressi-bility (15.72 kPa at a strain of 80%) and superior fatigue resilience (over 81% relative height retention after 100 cycles) (Fig. 4). The results of energy dispersive spectroscopy and infrared spectroscopy confirmed that the siloxane network structures were formed on the aerogel surface after MTMS modification (Fig. 3), endowing SMNF aerogel with superhydrophobicity (water contact angle of 150.9°) (Fig. 5). Consequently, MS aerogels demonstrated strong absorption capacity for various oil agents with the oil absorption capacity of 84.48-188.75 g/g (Fig. 7). More importantly, owing to the high elasticity and stable skeleton structure, MS aerogel displayed excellent repeatable oil absorption performance (Fig. 8, Fig. 9).

Conclusion Highly elastic and superhydrophobic MS aerogels were fabricated by urea/guanidine hydrochloride low eutectic solvent liquid phase exfoliation, freeze-induced assembly, and MTMS chemical vapor deposition modification. The assembled MS aerogels were characterized by hierarchical fibril networks and hierarchical cellular structures, which endowed MS aerogels with exceptional properties, including low density, high porosity and superelastic performance. Benefiting from the above features, the superelastic and superhydrophobic MS aerogel not only showed strong absorb ability to various oil agents, but also had excellent repeated oil absorption performance. This work provides a reliable approach for the fabrication of highly elastic and superhydrophobic SF aerogels and endows application prospects in oil absorption opportunities.

Key words: silk fibroin micro-nanofibril, aerogel, silicane modification, hyperelasticity, oil absorbency, mechanical property, hydrophobic property