No abstract

The thermal and mechanical properties of polysiloxane foam are greatly improved by the addition of acrylolsobutyl polyhedral oligomeric silsesquioxane (MA0701, hereinafter referred to as MAPOSS), which has double bonds. The morphologies and properties of the polysiloxane composite foam were characterized. The average cell diameter of the composite foams decreased, while the cell density increased with increasing MAPOSS. Meanwhile, MAPOSS can enhance thermal conductivity and thermal stability. Thermal conductivity increased by 25%, and the temperature at the maximum weight loss rate increased from 556 °C to 599 °C. In addition, MAPOSS also promoted heterogeneous nucleation by functioning as a nucleating agent, which can increase cell density to improve the mechanical properties. The compressive strength of the composite foam increased by 170% compared with that of pure foam. In the composite, MAPOSS increased the cross-linking density by acting as a physical cross-linking point and limited the movement of the segments.

Dynamic hydrogels constructed with dynamic chemical bonds often have mechanical strength and self‐healing properties. In this paper, tannic acid is combined with lysine‐containing F127 through Schiff base. A series of FLaT hydrogels cross‐linked by hydrogen bonds and dynamic chemical bonds is prepared, and the influence of Schiff base amount on the performance is discussed. The FLaT hydrogel exhibits reversible sol–gel transition, self‐healing, injectability, and pH sensitivity. Increasing the amount of Schiff base can improve the strength, stability, and self‐healing ability of the hydrogel. Owing to their low cytotoxicity, linear release pattern, and pH‐controlled release rate, the FLaT hydrogels show potential use in drug delivery systems for cancer treatment.

Mechanical exfoliation of graphene (MEG) and reduced graphene oxide (RGO) are fabricated with using graphite and they are used as fillers to improve the electromagnetic interference (EMI) shielding performance and thermal stability of polysiloxane composite foam. Since graphene builds a conductive network in the matrix and at the same time enhances the impedance mismatch between the syntactic foam and the external free space, the total shielding effectiveness (SE total ) of the composite foam can reach up to 4.74 dB, which is 500% higher than that of pure foam. Moreover, the layered structure of graphene can restrict the small molecules generated during the foam pyrolysis process from leaving the system, and also increases the maximum decomposition temperature of the composite foam (increased from 431.8 to about 500 C), which improves the thermal stability of the foam. These results indicate that the combination of graphene in polysiloxane foams produces composite foams with multifunctional properties, suitable for applications requiring EMI shielding and thermal performance.