Networks of single-wall carbon nanotubes (SWCNTs) are covalently functionalized with oxygen-containing groups. In lower concentration, these functional groups act as stable dopands improving the conductivity of the SWCNT material. In higher concentration however, their role as defects with a certain scattering potential becomes dominant, decreasing the conductivity of the CNT material. These effects lead to a trade-off in the number of functional groups which has been investigated using time-dependent sonochemistry.