Combined role of stearic acid and maleic anhydride in the development of thermoplastic starch-based materials with ultrahigh ductility and durability.

The diverse properties reported for starch-based materials indicate their potential for use in the preparation of biodegradable flexible actuators. However, their natural brittleness and lack of durability after modification limit their practical application. Therefore, we propose a strategy for preparing flexible starch-based composites. The results of macro/micro property characterizations and molecular dynamics simulations indicated that using starch, maleic anhydride, and stearic acid (SA), the mobility of the starch chains was enhanced and retrogradation was inhibited through the synergistic effects induced by chain breaking, complex formation with SA, and esterification of the starch molecules. In addition, the elongation at break of the modified starch (MS) reached 2070 %, and considerable ductility (>1000 %) as well as well-complexed structure were maintained after six months. Furthermore, the MS was able to undergo self-healing after fracture or a temperature-controlled stiffness transition. Moreover, it underwent complete degradation in soil within 30 d. Finally, an actuator was prepared by doping the MS with nano-Fe3O4 particles to realize a dual magnetic and optical response. Dynamic monitoring was also achieved based on the electrical signal, thereby demonstrating the broad application scope of this material in the development of biodegradable flexible actuators.

Starch-fiber foaming biodegradable composites with polylactic acid hydrophobic surface.

Starch and plant fibers are abundant natural polymers that offer biodegradability, making them potential substitutes for plastics in certain applications, but are usually limited by its high hydrophilicity, and low mechanical performance. To address this issue, polylactic acid (PLA) is blended with cellulose and chitosan to create a waterproof film that can be applied to starch-fiber foaming biodegradable composites to enhance their water resistance properties. Here, plant fibers as a reinforcement is incorporated to the modified starch by foaming mold at 260 °C, and PLA based hydrophobic film is coated onto the surface to prepare the novel hydrophobic bio-composites. The developed bio-composite exhibits comprehensive water barrier properties, which is significantly better than that of traditional starch and cellulose based materials. Introducing PLA films decreases water vapor permeability from 766.83 g/m2·24h to 664.89 g/m2·24h, and reduce hysteresis angles from 15.57° to 8.59° within the first five minutes after exposure to moisture. The water absorption rate of PLA films also decreases significantly from 12.3 % to 7.9 %. Additionally, incorporating hydrophobic films not only enhances overall waterproof performance but also improves mechanical properties of the bio-composites. The fabricated bio-composite demonstrates improved tensile strength from 2.09 MPa to 3.53 MPa.

Advances in chitosan-based wound dressings: Modifications, fabrications, applications and prospects.

In the field of medical research, the development of safe and effective wound dressings is a continuous goal. Chitosan (CS) is highly sought after because of its unique biocompatibility, biodegradability, antibacterial, and healing-promoting properties. The CS molecule has a significant number of active amino and hydroxyl groups; thus, making substitutions and creating derivatives with varied biochemical properties are relatively straightforward processes. This review addresses the range of functions performed by CS and its derivatives in wound care, such as haemostasis, antibacterial, antioxidant, and wound healing. Furthermore, it summarises the various types of CS-based dressings, their performance features and applications. Finally, the future directions of CS-based dressings are proposed.

A biodegradable chitosan-based composite film reinforced by ramie fibre and lignin for food packaging.

To solve the problem of environmental pollution caused by plastic food packaging films, a biodegradable chitosan-based film containing micro ramie fibre and lignin was prepared by the casting method. With the addition of different ratios of ramie fibre and lignin to the chitosan matrix, a significant improvement in mechanical, water resistance, thermal, and antioxidant properties was observed. The addition of 20 wt% ramie fibre increased the tensile strength by 29.6%. Moreover, the addition of 20 wt% of lignin increased the antioxidant activity by 288%, and reduced the water absorption by 41.2%. However, due to their high pyrolysis temperatures, there was little difference between ramie fibre and lignin in improving the thermal stability. Finally, this study compared the food preservation effects of composite films and PE films. The application evaluation results showed that the composite films were more effective. Overall, the chitosan-based films showed great potential for food packaging.