Dissolution of poly( vinyl alcohol)-modified carbon nanotubes in a buffer solution

Multiwalled carbon nanotubes (MWCNTs) were modified with a water-soluble poly( vinyl alcohol) (PVA) polymer (MWCNTs-PVA). The dissolution of the MWCNTs-PVA in Tris-HCl buffer solution was carried out in a shaking water bath by a soaking method. The microstructural changes of the MWCNTs-PVA during soaking was investigated using Fourier transform-infrared spectroscopy, differential scanning calorimetry, transmission electron microscopy, and X-ray diffraction. It is found that part of the MWCNTs-PVA was dissociated into amorphous carbonaceous debris, but most of tubular structures were retained after 21d of soaking. The dissolution process revealed that the C—C bonds of the MWCNTsPVA were broken-down with the generation of carbonaceous debris and residual carbon nanotube layers, and the latter can be further dissociated into amorphous carbonaceous debris. A possible dissolution mechanism of the MWCNTs-PVA in the buffer solution was proposed and discussed. The surface modified MWCNTs have many defects and open C—C bonds on the surfaces of the CNTs. The dissolution of the PVA in the buffer solution leads to a release of carbon atoms on the outer surface of the MWCNTs. It results in a further rupture of the C—C bonds and destroys the tubular structure .