β-Chitin nanofibrils for self-sustaining hydrogels preparation via hydrothermal treatment. 
A transparent nanofibril suspension could be readily obtained by treating purified squid pen powder in water with ultrasonic irradiation.  The obtained suspension is consisted of β-chitin nanofibrils (CNF) with 3-10 nm in width and several micrometers in length.  The degree of acetylation (DA) of CNF was found to be 84% which is about 10% lower than that of untreated sample.  The CNF suspension could be transformed into a durable 3-D hydrogels (CH) by simply heating to 180 °C for 1-4 h in an autoclave.  Hydrophobic interaction between CNF was believed to play the major role for CNF self-assembling into hydrogels, since the as-prepared chitin hydrogels readily dissolved in a typical chaotropic solution (8 M urea) under room temperature.  The hydrothermal duration and CNF concentration (0.3-2% (w/v)) strongly affected the physical properties of CH.  The suspension of 1% (w/v) CNF treated with 4 h, 180 °C hydrothermal heating generated a CH with 99.3% water content, CNF with 87% crystallinity and an mechanical strength of 0.7 N breaking force.