RESUMO
Polymers/polymer matrix composites possessing low dielectric constants (low-k polymer dielectrics) contribute to the advance of electronics, for instance, microprocessor chips, mobile phone antennas, and data communication terminals. However, the intrinsic long-chain structural characteristic results in poor thermal conductivities, which draw heat accumulation and undermine the outstanding low-k performance of polymers. Herein, multisource free-volume effects that combine two novel kinds of extra free volume with the known in-cage free volume of polyhedral oligomeric silsesquioxanes (POSSs) are discussed to reduce the capacity for dielectric constant reduction. The multisource free-volume effects of POSSs are associated with the thermal conductive network formed by the hexagonal boron nitride (BN) in the polymer matrix. The results show a decent balance between low-k performance (dielectric constant is 2.08 at 1 MHz and 1.98 at 10 GHz) and thermal conductivity (0.555 W m-1 K-1, 4.91 times the matrix). The results provide a new idea to maximize the free-volume effects of POSSs to optimize dielectric properties together with other desired performances for the dielectrics.
RESUMO
Current approaches to treating inflammatory bowel disease focus on the suppression of overactive immune responses, the removal of reactive intestinal oxygen species, and regulation of the intestinal flora. However, owing to the complex structure of the gastrointestinal tract and the influence of mucus, current small-molecule and biologic-based drugs for treating colitis cannot effectively act at the site of colon inflammation, and as a result, they tend to exhibit low efficacies and toxic side effects. In this study, nanogel-based multistage NO delivery microcapsules are developed to achieve NO release at the inflammation site by targeting the inflammatory tissues using the nanogel. Surprisingly, oral administration of the microcapsules suppresses the growth of pathogenic bacteria and increases the abundance of probiotic bacteria. Metabolomics further show that an increased abundance of intestinal probiotics promotes the production of metabolites, including short-chain fatty acids and indole derivatives, which modulate the intestinal immunity and restore the intestinal barrier via the interleukin-17 and PI3K-Akt signaling pathways. This work reveals that the developed gas therapy strategy based on multistage NO delivery microcapsules modulates the intestinal microbial balance, thereby reducing inflammation and promoting intestinal barrier repair, ultimately providing a new therapeutic approach for the clinical management of colitis.