ABSTRACT
Degumming is the most critical step for the silk textile industry and the process of silk-based advanced materials. However, current common degumming techniques are largely limited because of insufficient efficiency, obvious hydrolysis damage and difficulty in long-term storage. Here, deep eutectic solvent (DES) constituted of choline chloride (ChCl) and urea was explored to Bombyx mori silk fibers degumming without combining any further treatment. Compared to traditional alkali methods, DES could quickly remove about 26.5 % of sericin in just 40 min, and its degumming efficiency hardly decrease after seven cycles. Owing to the "tear off" degumming mechanism of DES molecules with "large volume", the resulted sericin has a large molecular weight of 250 kDa. In addition, because of antibacterial activity and stabilizing effect, no aggregation occurred and strong bacterial growth inhibition was triggered in the obtained sericin/DES solution. Furthermore, thanks to the good retention of crystalline region and slight swelling of amorphous area, the sericin-free fibroin showed significant increases in moisture absorption and dye uptake, while maintaining good mechanical properties. Featured with high efficiency, reduction in water pollution, easy storage of sericin as well as high quality fibers, this approach is of great potential for silk wet processing.
ABSTRACT
Owing to their small fiber diameter (10-15 µm), silk fabrics are always thin (32-90 g m-2). Therefore, construction of the Janus surfaces of silk fabrics that possess excellent multifunctionality remains a formidable challenge. Herein, first, silk fabrics were grafted using glycidyltrimethylammonium chloride to form a superhydrophilic surface (G-side). Then, a unilateral hydrophobic surface (O-side) was readily fabricated by mist coating octadecyltrichlorosilane-functionalized SiO2 nanoparticles (NPs) to produce hierarchical surface textures. To prevent NP penetration from the G-side to the O-side, a "fireproof isolation" method was employed. Consequently, Janus silk fabrics (JanSFs) bearing asymmetric wettability were prepared, and their wetting gradient could be conveniently regulated. With the mist time ranging from 4 to 7 min, the unidirectional transport index and efficiency of the unidirectional water transport increased and decreased by 13.2 and 10.4 times, respectively. Sweat could be effectively drained away from human skin to ensure that the skin was dry and comfortable. Compared with the surface temperature of the raw fabric, the raw fabric of JanSFs increased by 2.7 °C. Furthermore, the breathability of JanSF was negligibly affected, and the outer O-side of the JanSF showed substantial antibacterial activity. This study is important for designing JanSFs that exhibit unidirectional water transport.
