Measurement in the frequency range 3 mHz–106 Hz of the dielectric characteristics ofemeraldine base polyaniline dissolved in 1-methyl-2-pyrrolidinone (NMP) andcast into bulk free-standing polymer films shows features similar to thosereported by others and which are a result of microphase separation intoreduced and oxidized repeat units. However, upon confinement into thecylindrical pores, of average diameter 20 nm, of a porous membrane suchfeatures of microphase separation do not occur. Strong pinning of the chargecarriers due to interactions of the polymer with pore walls together withconstrained chain packing and a non-uniform rate of evaporation of theNMP solvent from the pores suggests that the microphase separationobserved in the bulk polymer is suppressed. This has the potential ofbeing able to enhance the bulk conductivity after doping by reducingthe internal intrachain disorder introduced by microphase separation.