We developed a highly efficient magnetic relaxation switch (MRS) system based on poly(vinyl alcohol) functionalized nanomagnetic iron oxide (PVA@NMIO) particles for the detection of boric acid or borate ester (BA/BE). It was found that the addition of BA/BE induced the aggregation of PVA@NMIO particles, resulting in a measurable change in the T2 relaxation time in magnetic resonance measurements. The main mechanism was proposed that the electron-deficient boron atoms of BA/BE caused the aggregation of PVA@NMIO particles through covalent binding to the hydroxyl groups of PVA. This novel detection system displayed excellent selectivity, high sensitivity, and rapid detection for BA/BE. Thus, this system may provide a great application prospect for detection of BA/BE.
Haoxin Niu,Yu Li,Ping Zhang,Wenwen Guo,Xin Wang,Yuan Hu
Due to their excellent properties, thermosetting polymer materials have been widely used in many fields. Owing to the restriction of the crosslinked network, traditional thermosetting polymer materials exhibit insolubility and immiscibility. Therefore, the reprocessing of thermosetting polymer materials is a great challenge. With the depletion of petroleum-based resources, the utilization of natural resources for the preparation of bio-based thermosetting polymer materials is a major trend. In this study, eugenol-based covalent adaptable thermosets were prepared via UV curing and thermal curing according to thiol click chemistry. The mechanical properties of the eugenol-based covalent adaptable thermosets, which are better than those of the control sample, can be regulated according to the components. The eugenol-based covalent adaptable thermosets exhibited excellent transparency and UV shielding properties. The introduction of a dynamic covalent boronic ester (BSH) promoted the formation of residual char and enhanced the fire safety of the eugenol-based covalent adaptable thermosets. Owing to the dynamic borate ester bonds in the cross-linked network, the eugenol-based covalent adaptable thermosets exhibited significant stress relaxation behavior, and excellent shape memory function and self-healing properties. The samples were reprocessed at 100 °C several times. After three cycles of pulverizing and hot pressing, the recovery ratio of tensile strength of the reprocessed samples remained above 85%. This study provides a novel strategy for preparing self-healable, reprocessable and anti-flammable covalent adaptable thermosets with tunable mechanical properties.
危险品化学品经营许可证（带存储）