Particularly in dense CNT assemblies, FET device performance is crucially determined by the topology of SWCNTs. Therefore we have explored a new approach allowing to tune channel properties by a direct post synthesis of poly (sodium 4-styrenesulfonate) (P(NaSS)) on SWCNTs. It reveals to be highly beneficial in improving the device parameters such as improved device-to-device consistency, higher drain currents and higher on/off ratios. Moreover, this treatment may serve also as a long-term passivation of SWCNT transistor devices. (M.Toader et al. in Chemical Physics Letter (2016) 10.1016/j.cplett.2016.07.049)