Different thermoplastic polyurethane (TPU) nanocomposites with various amounts of halloysite nanotube (HNT) were prepared. The morphological, rheological, thermal, mechanical, and electrical properties of the nanocomposites were also investigated. Fourier‐transform infrared spectroscopy shows that increasing HNT results in increased degree of phase separation. Differential scanning calorimetry thermograms indicate positive effects of HNT on the hard phase crystallinity due to interactions between the surface functional groups of nanotubes and the polyurethane hard phase and also disinclination to form spherulites. According to the dynamic mechanical thermal analysis results, storage modulus of the nanocomposites increased up to 185% with increasing the HNT content in the experimental temperature window, which is in accordance with the tensile strength results. Mechanical analysis indicates that the modulus of nanocomposite increased up to 122% with increasing the HNT content. Rheo‐mechanical spectroscopy results showed that by the addition of low contents of HNT into the TPU matrix, the storage modulus did not show significant variations; however, an upturn in storage modulus was observed by increasing the amount of HNT to 4.2 wt%. In addition, the average volume conductivity of HNT‐reinforced nanocomposites was decreased comparing to the pure TPU even at low amounts of HNT. Therefore, addition of HNT into the TPU matrix resulted in higher mechanical properties in the related nanocomposites.

Polyurethane composites were synthesized using carbon nanotube (CNT) and CNT‐halloysite (HNT) hybrid in different amounts. Thermal, rheological, and mechanical properties of the composites were studied using thermogravimetric analysis, rheometrics mechanical spectrometry, dynamic mechanical thermal analysis, stress‐strain analysis, and hardness measurement. In this context, phase separation, elastic modulus, the Young's modulus, damping, tensile strength, ductility, thermal degradation, hardness, and conductivity were measured and discussed in detail. Modulus, tensile strength, and hardness were increased by 69%, 29%, and 1%, respectively, with incorporation of CNT, while tensile strength was reduced in the hybrid composites containing CNT‐HNT hybrid. In addition, hard and soft segment phase separation and melting points were increased up to 0.8% and 21%, respectively, by the addition of CNT. However, these characteristics were reduced with the addition of CNT‐HNT hybrid in the related composites. Uniform dispersion of HNT and CNT in the polyurethane matrix is clearly shown in the transmission electron microscopy images.

No abstract

Cobalt‐catalyzed has attracted much attention, and being used to the total synthesis of a wide range of naturally occurring compounds having complex structures. The chemist of natural products is a distinct part of chemical research that has been important in the history of chemistry, pharmacology, the finding of substances in initial preclinical drug discovery research, and also the understanding of folk medicine. The Cobalt‐catalyzed reaction has frequently been used as a key step (steps) in the total synthesis of natural products and targeted complex bioactive molecules. In this review, we want to show the application of cobalt‐catalyzed reactions in the synthesis of natural products having biological activities from 2000 till date.