Yangyi Sun

Homeostatic microfiber leathers with temperature self-regulation promise broad applications, ranging from the apparel and automotive interior industries to the home furnishing and healthcare industries. Temperature self-regulation is achieved by phase-change materials containing microcapsules introduced within the leathers. The introduction of phase change microcapsules (PCMs) into microfiber leather faces two formidable challenges: (1) the shell of microcapsules must remain chemically stable against alkalis and organic solvents; (2) PCMs possess the ability to reduce supercooling during which latent heat is released, allowing for the precise and controllable release of latent heat. Here we present a high-performance homeostatic microfiber-composed synthetic leather containing PCMs that can address these two challenges, which not only demonstrate exceptional chemical robustness under alkaline conditions but also offer efficient and precise control over temperature fluctuation and latent heat release by reducing supercooling. Titanium carbide (TiC) known for its high thermal conductivity and alkali resistance has been selected as the shell material for the microcapsules, which can effectively resolve chemical stability issues. Meanwhile, the high thermal conductivity of TiC can be leveraged to enhance heterogeneous nucleation, thus narrowing the temperature range for latent heat release. The resultant microfiber leather shows outstanding capabilities for adjustable thermal energy storage. Our studies offer an effective approach to create homeostatic microfiber-composed synthetic leathers with chemical robustness and undercooling self-regulation, which would be useful in the fields of the textile, biomedical, and healthcare industries.

Numerous cationic magnetic nanoparticles (MNPs) have previously been developed for demulsifying oil-in-water (O/W) emulsion, and results showed that the cationic MNPs could effectively flocculate and remove the negatively charged oil droplets via charge attraction; however, to the best of our knowledge, there are no research reports regarding the synergetic influence of both the positive charge density and interfacial activity of MNPs on the demulsification performance. In this study, three tertiary amine polymer-grafted MNPs, namely, poly(2-dimethylaminoethyl acrylate)-grafted MNPs (M-PDMAEA), poly(2-dimethylamino)ethyl methacrylate)-grafted MNPs (M-PDMAEMA), and poly(2-diethylaminoethyl methacrylate)-grafted MNPs (M-PDEAEMA), were synthesized and evaluated for their demulsification performance. Results demonstrated that a high positive charge density and superior interfacial activity of MNPs could cause partial oil droplet re-dispersion when excessive MNPs were introduced, leading to a lower magnetic separation efficiency and narrower demulsification window. Herein, a demulsification window is defined as a range of nanoparticle dosages in which the MNPs can effectively demulsify the O/W emulsion under certain conditions. For highly positively charged MNPs, their good interfacial activity could aggravate the formation of a narrower demulsification window. When tertiary amine polymer-grafted MNPs carried a lower positive charge density or weak interfacial activity, that is, M-PDMAEA at pH 4.0, M-PDMAEMA at pH 5.0-9.0, and M-PDEAEMA at pH 9.0-10.0, wide demulsification windows were observed. Additionally, a recycling experiment suggested that MNPs could maintain high demulsification efficiency up to at least five cycles, indicating their satisfactory recyclability. The three tertiary amine polymer-grafted MNPs can be potentially used for efficient demulsification from surfactant-free O/W emulsion in various pH ranges.