Nanohybrid shish-kebabs:: Supercritical CO2-induced PE epitaxy on carbon nanotubes

In this study, we develop a facile and efficient method for period-decorating carbon nanotubes (CNTs) using a supercritical (SC) CO2 anti solvent-induced polymer epitaxy (SAIPE) method. It helps the epitaxy growth of PE on CNTs under a series of suitable experimental conditions, forming a nanohybrid shish-kebab (NHSK) structure. With the variation of a series of experimental conditions or peripheral effect, such as different solvent, PE concentration, CNTs concentration and SC CO2 pressure, the NHSK structure, i.e., the size of the lamellae and the interval between them along the stem, can be varied. When p-xylene was used as the solvent for PE and single-walled CNT (SWCNT), the size of the lamellae can be adjusted from 80-120 to 125-250 nm with the change of the PE concentration. Using the same solvent p-xylene, with the change of SC CO2 pressure, the size of the lamellae can be changed from 125-250 to 300-400 nm. When dichlorobenzene (DCB) was used as the solvent for PE and SWCNT, with the increase of the SWCNT concentration, from 0.002 to 0.006 and 0.01 wt %, the size of the lamellae can be reduced from 305-420 to 280-400 and 85-200 nm. In comparison to the experimental result with p-xylene used as the solvent, it is found that the decorated CNTs have more excellent dispersion when DCB was used as the solvent. Our experimental results indicate that the SAIPE method is effective for both SWCNTs and multiwalled CNTs (MWCNTs). Therefore, this work not only provides a new route to periodically functionalize CNTs with a controllable and adjustable method, but also it can be anticipated to open a gateway for making use of peculiar properties of SC CO2 to help functionalize CNTs in an environmentally benign manner.