The present application relates to thin film transistors having a semiconducting channel comprising a network of carbon nanotubes that are electrically coupled to a source electrode and a drain electrode and electrically insulated from, but capacitively coupled to, a gate electrode, wherein a polymeric layer encapsulates the carbon nanotubes. The polymeric layer can comprise a first monomeric unit and optionally a second monomeric unit, wherein the first monomeric unit, the second monomeric unit and the relative amounts thereof are optionally selected to provide at least one target electrical property of the thin film transistor. The present application also relates to methods for manufacturing such thin film transistors as well as a methods of selecting a polymeric layer to provide a desired threshold voltage for such thin film transistors.