Conductive polymers, i.e. plastics, that conduct electricity, are important in science and technology as they offer the potential for cheap, flexible electronic devices. This work examines the mechanisms by which electrons are transported in such materials, a process that remains far from understood. One of the main results of the work is that the behavior of such materials, at very high densities of charge carriers, is radically different to simple expectations. In particular, it is found that the typical methods used to “dope” the materials, i.e. to increase their conductivity, can create large amounts of disorder in the polymer material, preventing the expected transition to metallic behavior. The result has important consequences for design of future polymer electronic devices.