The preparation and mechanical properties of elastomeric nanocomposite hydrogels consisting of cellulose nanocrystals (CNCs) and poly(ethylene glycol) (PEG) are reported. The aqueous nanocomposite CNC/PEG precursor solutions covalently cross-linked through a one-stage photocross-linking process. The mechanical properties of nanocomposite hydrogels, including Young's modulus (E), fracture stress (σ), and fracture strain (ε), were measured as a function of CNC volume fraction (φCNC, 0.2-1.8%, v/v) within polymeric matrix. It was found that the homogeneously dispersed nanocomposite hydrogels can be prepared with φCNC being less than 1.5%, whereas the heterogeneous nanocomposite hydrogels were obtained with φCNC being higher than 1.5%. The nanocomposite hydrogels exhibited higher strengths and flexibilities when compared with neat PEG hydrogels, where the modulus, fracture stress, and fracture strain enhanced by a factor of 3.48, 5, and 3.28, respectively, over the matrix material alone at 1.2% v/v CNC loading. Oscillatory shear data indicated the CNC-PEG nanocomposite hydrogels were more viscous than the neat PEG hydrogels and were efficient at energy dissipation due to the reversible interactions between CNC and PEG polymer chains. It was proposed that the strong gel viscoelastic behavior and the mechanical reinforcement were related to "filler network", where the temporary interactions between CNC and PEG interfered with the covalent cross-links of PEG.

Although self-healing gels with structural resemblance to biological tissues attract great attention in biomedical fields, it remains a dilemma for combination between fast self-healing properties and high mechanical toughness. On the basis of the design of dynamic reversible cross-links, we incorporate rigid tannic acid-coated cellulose nanocrystal (TA@CNC) motifs into the poly­(vinyl alcohol) (PVA)–borax dynamic networks for the fabrication of a high toughness and rapidly self-healing nanocomposite (NC) hydrogel, together with dynamically adhesive and strain-stiffening properties that are particularly indispensable for practical applications in soft tissue substitutes. The results demonstrate that the obtained NC gels present a highly interconnected network, where flexible PVA chains wrap onto the rigid TA@CNC motifs and form the dynamic TA@CNC–PVA clusters associated by hydrogen bonds, affording the critical mechanical toughness. The synergetic interactions between borate–diol bonds and hydrogen bonds impart a typical self-healing behavior into the NC gels, allowing the dynamic cross-linked networks to undergo fast rearrangement in the time scale of seconds. Moreover, the obtained NC hydrogels not only mimic the main feature of biological tissues with the unique strain-stiffening behavior but also display unique dynamic adhesiveness to nonporous and porous substrates. It is expected that this versatile approach opens up a new prospect for the rational design of multifunctional cellulosic hydrogels with remarkable performance to expand their applications.

Nanocomposites have drawn a great interest in materials science of elastomers in recent years, and tailoring interfacial interactions between fillers and polymer matrix plays a critical role in improving their mechanical properties. The synthetic platform of tough and stretchable cellulose nanocrystal−poly(acrylamide) (CNC−PAM) composite hydrogels was proposed and applied here to unravel the role of covalent network in PAM and physical interactions by CNC surface adsorption. The attractive physical interactions in the network were considered to increase the fracture strength of the hydrogels via reversible adsorption−desorption processes on the CNC surface. Stress-sensitive characteristic shifts of the Raman peak located at 1095 cm −1 indicated an efficient load transfer across the interface, where the tensile modulus was higher than the compression modulus. In situ transmission electron microscopy observation allowed to demystify the composites deformation process and interfacial bridging between CNC and polymer matrix. A detailed comparison of strain rate effect on large strain dissipation indicated that the viscoelastic behavior of the hydrogels varied remarkably over strain rates, ranging from little hysteresis at low strain rates to highly dissipative at high strain rates, suggesting a new, slow relaxation mode, most likely due to interfacial adsorption of polymer chains on the CNC surfaces. This study showed that polymer chains desorbed from the CNC surface under periodic strains would entangle with the free chains after the rest time via conformational rearrangements, consequently triggering a recovering mechanism during multiple crazing and shear relaxation processes.

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The scientific name of the traditional Chinese medicinal fungus, Sanghuang , has been clarified and confirmed that it is a new species - Sanghuangporus sanghuang in the recently discovered genus, Sanghuangporus . To maximize the yield of the active ingredients such as the triterpenoids from authentic Sanghuangporus sanghuang , four parameters of the extraction process, including the extraction time, solid–liquid ratio, extraction temperature, and ethanol concentration were determined. The Box–Behnken experimental design and the response surface method were used to optimize the triterpenoid extraction processes of Sanghuangporus sanghuang mycelium. The results showed that the parameters of the triterpenoid extraction processes were not simple linear relationships. Optimum conditions of ultrasonic extraction required an 80% ethanol concentration, a 1:20 solid–liquid ratio, a 20-min extraction time, and a 60 °C extraction temperature, to obtain a maximum triterpenoid extraction of 13.30 mg/g. Antioxidant capacity tests showed that the Sanghuangporus sanghuang triterpenoids had high clearance capabilities for hydroxyl free radicals, superoxide anions, 2,2-diphenyl-1-picrylhydrazyl free radicals, and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulfonate) radicals, indicating that the Sanghuangporus sanghuang triterpenoids had high antioxidant activities.