Double-network (DN) hydrogels with high strength and toughness have been developed as promising materials. Herein, we explored a dual physically cross-linked polyacrylamide/xanthan gum (PAM/XG) DN hydrogel. The nonchemically cross-linked PAM/XG DN hydrogels exhibited fracture stresses as high as 3.64 MPa (13 times higher than the pure PAM single network hydrogel) and compressive stresses at 99% strain of more than 50 MPa. The hydrogels could restore their original shapes after continuously loading-unloading tensile and compressive cyclic tests. In addition, the PAM/XG DN hydrogels demonstrated excellent fatigue resistance, notch-insensitivity, high stability in different harsh environments, and remarkable self-healing properties, which might result from their distinctive physical-cross-linking structures. The attenuated total reflectance infrared spectroscopy (ATR-IR) and dynamic thermogravimetric analysis (TGA) results indicated that there were no chemical bonds (only hydrogen bonds) between the XG and PAM networks. The PAM/XG DN hydrogel synthesis offers a new avenue for the design and construction of DN systems, broadening current research and applications of hydrogels with excellent mechanical properties.

ABSTRACT:The biodegradation of poly(butylene succinate) (PBS) was studied under controlled composting conditions. The ultimate biodegradation percentage revealed that the powder-formed sample showing the best biodegradability may be ascribed to the largest specific surface. The biodegradation process of PBS under controlled composting conditions exhibited three phases. The biodegradation in the first phase was slow, got accelerated in the second phase, and showed a leveling-off in the third phase. The degradation of PBS film after composting was further characterized by gel permeation chromatography (GPC) and scanning electron microscopy (SEM). Four strains were isolated from the compost and identified as Aspergillus versicolor, Penicillium, Bacillus, and Thermopolyspora. Their degrading abilities to PBS powder in liquid medium were different. Among them, Aspergillus versicolor was the best PBS-degrading microorganism.

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