Synthesis and characterization of poly methyl methacrylate-b-polystyrene copolymer/ multi -walled carbon nanotubes via ATRP and NMRP techniques

Graft polymerization of polymethyl methacrylate–block-polystyrene (PMMA-b-PSt) has been carried out from the surface of multi-walled carbon nanotubes (MWCNTs) using living radical polymerization methods. For this purpose, the first surfaces of MWCNTs were functionalized by acid treatment and then acylated by thionyl chloride (SOCl2). After that, the toluene unit was successfully grafted onto MWCNTs side walls by Friedel craft acylation reaction in the presence of ZnO as a catalyst. The obtained nanotube-toluene was brominated by N-bromosuccinimide (NBS). This brominated nanotube-toluene was used as a macroinitiator for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in the presence of the CuBr/ 2, 2 -bipyridine (bpy) catalyst system to obtain MWCNTs-graft-polymethyl methacrylate (MWCNTs-g-PMMA). Then 1-hydroxy-2, 2, 6, 6-tetramethyl-piperidine (TEMPO-OH) obtained by reduction of 2, 2, 6, 6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbate. The bromine groups at the end of PMMA have converted to nitroxide mediated groups by coupling with TEMPO-OH to yield MWCNTs terminated with a TEMPO unit (MWCNTs-PMMA-TEMPO). At last, the resulting macroinitiator was employed for ‘living’ free-radical polymerization of styrene (St) by nitroxide-mediated radical polymerization (NMRP) to form MWCNTs-g-(PMMA-b-PS). Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) show the effective grafting of MMA and styrene onto the MWCNTs.