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A skin-like cellulose biomimetic hydrogel was prepared based on dynamic covalent chemistry, which realized the combination of ultra-stretchability, self-healing, adhesiveness, antibacterial and mechano-stimuli sensitivity within a single structure.

A facile, environmentally benign approach has been developed for the preparation of dynamic, multiresponsive, and self-healing hydrogels from inexpensive bamboo pulp, poly(vinyl alcohol) (PVA), and borax. The microfibrillated cellulose (MFC) reinforced PVA−borax hydrogels were produced through a onepot route in conjunction with ball milling and physical blending in tandem in aqueous medium. In this way, MFC particles could be efficiently generated and well-dispersed in a polymer matrix, and they have been verified by scanning electron microscopy. The rheology analysis indicated a close relationship between the mechanical strength and the MFC loading and ball milling time. Due to the dynamic equilibrium of the didiol−borax linkages and the reinforcement of MFC fibers, the hydrogels showed enhanced self-healing behavior and mechanical stiffness, which was also supported by rheology analyses. In addition, the hydrogels were found to be sensitive to the pH value. The hydrogels present a solvent or gel state with the change of pH value, and this sol−gel transfer can be repeated while maintaining the shape, further demonstrating the dynamic reversible behavior of the hydrogels.

An efficient approach for extracting cellulose nanocrystals (CNCs) was put forward through phosphotungstic acid (PTA) hydrolysis of cellulose raw materials under mechanochemical activation. Response surface methodology was employed for experimental design to determine the optimum conditions of CNCs preparation with software Design Expert. The results showed that quadratic polynomial model was qualified to represent the relationship between the response and independent variables and the regression model defined well the true behavior of the system. Under the optimal conditions, a high yield of up to 88.4%, crystallinity index of 79.6%, and a higher thermal stability can be achieved by combining mechanochemical activation and phosphotungstic acid hydrolysis. This process can improve effectively the hydrolysis efficiency, avoid a lengthy separation process, and reduce the preparation time. Meanwhile, compared to other techniques, mechanochemical activation is an energy-intensive method, and the process is environment-friendly. Phosphotungstic acid hydrolysis is easier to handle than liquid acids; meanwhile, the catalyst causes fewer corrosion hazards and can readily be recycled. Thus, an efficient green high-yield approach for the preparation of CNCs was achieved in the study.

The development of a chiral-at-metal iridium(III) complex for the highly efficient catalytic asymmetric transfer hydrogenation of β,β'-disubstituted nitroalkenes is reported. Catalysis by this inert, rigid metal complex does not involve any direct metal coordination but operates exclusively through weak interactions with functional groups properly arranged in the ligand sphere of the iridium complex. Although the iridium complex relies only on the formation of three hydrogen bonds, it exceeds the performance of most organocatalysts with respect to enantiomeric excess (up to 99% ee) and catalyst loading (down to 0.1 mol %). This work hints at an advantage of structurally complicated rigid scaffolds for non-covalent catalysis, which especially relies on conformationally constrained cooperative interactions between the catalyst and substrates.

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A bioinspired hydrogen bond crosslink strategy enabled the physical hydrogels to possess exceptional mechanical properties, good self-recoverability, versatile adhesiveness, biocompatibility and antibacterial properties.