Ultrathin Nanosheets of Organic-Modified β-Ni(OH)2 with Excellent Thermal Stability: Fabrication and Its Reinforcement Application in Polymers

beta-Nickel hydroxide (beta-Ni(OH)(2)), which combines two-dimensional (2D) structure and the catalytic property of nickel-containing compounds, has shown great potential for the application in polymer nanocomposites. However, conventional beta-Ni(OH)(2) exhibits large thickness, poor thermal stability, and irreversible aggregation in polymer matrices, which limits its application. Here, we use a novel phosphorus-containing organosilane to modify the beta-Ni(OH)(2) nanosheet, obtaining a new beta-Ni(OH)(2) ultrathin nanosheet with excellent thermal stability. When compared to pristine beta-Ni(OH)(2), the organic-modified beta-Ni(OH)(2) (M-Ni(OH)(2)) maintains nanosheet-like structure, and also presents a small thickness of around 4.6 nm and an increased maximum degradation temperature by 41 degrees C. Owing to surface organic-modification, the interfacial property of M-Ni(OH)(2) nanosheets is enhanced, which results in the exfoliation and good distribution of the nanosheets in a PMMA matrix. The addition of M-Ni(OH)(2) significantly improves the mechanical performance, thermal stability, and flame retardancy of PMMA/M-Ni(OH)(2) nanocomposites, including increased storage modulus by 38.6%, onset thermal degradation temperature by 42 degrees C, half thermal degradation temperature by 65 degrees C, and decreased peak heat release rate (PHRR) by 25.3%. Moreover, it is found that M-Ni(OH)(2) alone can catalyze the formation of carbon nanotubes (CNTs) during the PMMA/M-Ni(OH)(2) nanocomposite combustion, which is a very helpful factor for the flame retardancy enhancement and has not been reported before. This work not only provides a new 2D ultrathin nanomaterial with good thermal stability for polymer nanocomposites, but also will trigger more scientific interest in the development and application of new types of 2D ultrathin nanomaterials.