Self-assembly behavior of carbon nanotubes modified by amphiphilic block copolymer

Block copolymers of poly(tert-butyl methyacrylate) (PtBMA) and polystyrene (PSt) were grafted onto multi-walled carbon nanotubes (MWNTs) by the reaction of azide groups at the copolymer chain end with the surface of MWNTs. After hydrolysis, PtBMA block was transformed to polymethyacrylic acid (PMAA) block, and amphiphilic diblock copolymer-modified MWNTs were finally obtained. The modified MWNTs were characterized by XPS, TGA, FTIR, and Raman, and the results showed that the amphiphilic diblock copolymers were grafted onto MWNTs by the covalent bond. The TEM and SEM observation showed that PMAA-b-PSt copolymer modified MWNTs (S2) formed self-assembly tube bundles with the size up to 20 μm in both ethanol and chloroform. However, PtBMA-b-PSt copolymer modified MWNTs (S1) only formed small-size aggregates or dispersed as single-modified MWNTs. The dispersion stability tests showed that S1 had good dispersion stability in several solvents (water, ethanol, acetone, and chloroform) even after 20 days. Due to the big-size tube bundles formed by self-assemble S2, the dispersion stability of S2 in above all solvents decreased, but it was still much better than that of pristine MWNTs.