Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was grafted onto the bromine-functionalized multiwalled carbon nanotubes (MWNTs) by applying an atom transfer radical polymerization (ATRP). The PDMAEMA-functionalized MWNT was characterized by Fourier transform infrared, transmission electron microscopy, Raman spectroscopy, thermal gravimetric analysis, and four-probe resistivity meter. The wt % of PDMAEMA present in the PDMAEMA-functionalized MWNT was estimated by applying the thermogram results for thermal gravimetric analysis. Variations of PDMAEMA content in the PDMAEMA-functionalized MWNT were tried by changing the ATRP process conditions such as the type of ligand and copper complex, the amount of DMAEMA based on the weight of bromine-functionalized MWNT, and the polymerization temperature. The phase behavior of PDMAEMA-functionalized MWNT in water depending on temperature and pH value was analyzed, and the PDMAEMA-functionalized MWNT showed the amphipathic nature. The PDMAEMA-functionalized MWNT clearly showed an antibacterial effect against E. coli as well as S. aureus. The highest viability loss of E. coli achieved in this study was 42% with the PDMAEMA-functionalized MWNT containing 53.9 wt % of PDMAEMA. The PDMAEMA-functionalized MWNT showed sheet resistance less than 9.68 x 10(3) Omega/sq. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 127: 1508-1518, 2013