This work provides a new method to prepare poly(vinyl alcohol) (PVA) hydrogel. Compared with the traditional repeated freeze−thaw method, the physical cross-linking method was adopted to prepare a high-strength hydrogel in one step. The morphology, melting, and crystallization behavior and mechanical properties of the hydrogel were investigated. The hydrogel has a high water content and reswelling rate, as well as a high melting temperature and mechanical strength. It also has a stable crosslinked structure in the temperature range of 25−65 °C. The hydrogel fracture surface shows ductile and brittle fracture morphology. The protrusions in the hydrogel three-dimensional topography are more numerous and homogeneous when the solvent preparation ratio is 4−6. On the basis of the good plasticity of the hydrogels, tubular hydrogels with inner diameters of 1−6 mm are also prepared to widen their applications.

Efficient and facile catalytic protocols for chlorination and ligand-directed ortho-acetoxylation of 2-arylbenzoxazoles have been developed. The chlorination is not a ligand-directed ortho-functionalization, but an electrophilic substitution process in the benzo ring of the benzoxazole moiety. Meanwhile, the acetoxylation exhibited high regioselectivity for the substrates containing a meta-substituent and occurred at the less sterically hindered ortho-C-H bond of the directing group.

A composite of poly(ethylene oxide) (PEO) and lignin (Lg) was prepared and characterized for its utility as an ultraviolet (UV) absorbing material. Due to the extensive UV absorption and excellent oxidation-resistance of Lg, the formation of hydrogen bonds between the Lg particles and the PEO molecular segments renders the Lg particles well-dispersed in the PEO matrix. PEO/Lg composites with different Lg contents show that high levels of Lg could cause defects at the PEO/Lg composite interface. The viscosities of all composites were higher than that of pure PEO. Composite foams were further prepared under supercritical carbon dioxide conditions, all of which exhibited excellent UV-absorption properties. This work provides a means toward convenient preparation of PEO composites with UV-absorption ability and forms a theoretical basis for the dispersion of Lg in polymer matrices.

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