Novel poly(vinyl alcohol)/carbon nanotube nanocomposite microspheres prepared via suspension polymerization and saponification

Poly(vinyl acetate) (PVAc)/poly(vinyl alcohol)/carbon nanotube (CNT) nanocomposite microspheres with a core/shell structure were prepared by heterogeneous saponification of a PVAc/CNT microsphere suspension polymerized for the first time. We investigated the effects of various polymerization conditions on the conversion of vinyl acetate (VAc) into PVAc, such as time, temperature, and CNT concentration. The results indicated that the rate of polymerization decreased with CNT addition. In addition, the time and temperature had significant effects on the polymerization rate, and it was difficult to obtain higher conversion of VAc into PVAc at lower temperature and time. However, 65% conversion could be achieved despite the presence of CNTs at low temperature for a polymerization time of 25 h. Field-emission scanning electron microscopy was performed to examine the CNT distribution in the PVAc microspheres, and the results revealed that CNT particles were completely inserted into the polymer matrix, indicating that PVAc/CNT microspheres could be prepared by in situ suspension polymerization. The detailed structure of the PVAc/CNT microspheres was determined using X-ray diffraction analysis, and the results suggested that CNTs were inserted into PVA microspheres, and PVAc/CNT nanocomposite microspheres were successfully prepared with 0.5 wt.% CNTs. The effects of various CNT concentrations on the degree of saponification of PVAc were examined using optical microscopy at various saponification times, and ¹H-NMR results indicated that the saponification rate increased significantly with increasing CNT concentration and that almost fully saponified PVA microspheres were obtained in the presence of 0.5 wt.% CNTs for a saponification time of 120 h.