Supercritical CO2 assisted poly(vinylidene fluoride) wrapping on carbon nanotubes

Poly(vinylidene fluoride) (PVDF) has attracted much attention due to its mechanical strength and piezoelectric properties, and has been widely used in diverse fields. Carbon nanotubes (CNTs) have been considered as ideal reinforcing fillers for polymer because of extraordinary mechanical strength and high electrical conductivity. The PVDF/CNTs composite will be promising and of great potential applications in electromechanical devices design considering their attractive electrical and mechanical properties from PVDF and CNTs. In this study, we develop a controllable and adjustable method for noncovalent wrapping CNTs with PVDF using a supercritical (SC) CO₂ antisolvent-induced polymer epitaxy method, which have a great potential to improve the compatibility between CNTs and polymer. Transmission electron microscopy (TEM) results showed that with the variation of experimental conditions, the micro morphology of the obtained materials can be varied. For the single-walled CNTs (SWCNTs), with the increase of SC CO₂ pressure, the PVDF wrapping degree on SWCNTs increases. In further study we can find that there is the formation of the nanohybrid structure with nanocrystals wrapping on SWCNTs. Firstly, a few of molecular chains precipitated on the surface of SWCNTs, and then form a primary particle from several nucleuses, and followed it might grow as a spathic nanocrystal. During the process, the PVDF nanocrystals on the SWCNT could be regarded as a steady intermediate state, which could further form ordered patterning of nanohybrid structure when suitable experimental conditions are achieved.