Whether considering the voids and nanofibrillar domains within crys-PEDOT:PSS, the PEDOT-rich versus PSS-rich domains within EG/GOPS-PEDOT:PSS, or the crystalline and amorphous domains in pg2T-TT, the distribution of ions throughout OMIECs is not necessarily homogenous. In the case of EG/GOPS-PEDOT:PSS, the meso-scale structure is a mixture of PEDOT-rich and PSS-rich domains. Thus, passive cation-proton exchange is expected to lead to higher metal cation concentrations within the PSS-rich domains than the PEDOT-rich domains. Semi-crystalline pg2T-TT is presumed to present ordered/crystalline domains embedded in an amorphous matrix, similar to well-studied alkyl-side chain polythiophenes. Spectroscopic studies on closely related alkyl-sidechain materials have been interpreted as indicating a potential-dependent differential distribution of dopant ions between the amorphous and crystalline regions. Thus, to further understand the distribution of ions in OMIEC films, we performed ex situ GISAXS experiments collecting 2-D small angle scattering patterns from films as prepared (neat), after electrolyte exposure, and after electrochemical (re/de)-doping. In GISAXS, the changes in feature positions indicate a change in mesoscale structure on exposure/electrochemical biasing, where as a change in feature intensity decay would be an indicator of changes in electron density associated with ionic/water distributions. 2-D ex situ GISAXS patterns were collected for EG/GOPS-PEDOT:PSS films neat/as cast, electrolyte exposed, electrochemically dedoped (-0.6 V vs Ag/AgCl), and electrochemically redoped to a roughly equilibrium oxidation state (0.0 V vs Ag/AgCl) (Figure ). Line-cuts from all the films conditions displayed a similar broad scattering feature between 0.01 and 0.03 Å -1 (Figure ), indicating that mesoscale structure (phase separation of PEDOT-rich and PSSrich domains) is essentially constant due to high level of crosslinking, with a domain length-scale in keeping with previous investigations. With ex situ exposed and biased films, the changes in small angle scattering intensity are ascribed to larger changes in cation concentration within the PEDOT-rich domains compared to the PSS-rich matrix. The exposed (having undergone proton-cation exchange) and redoped line cuts were nominally identical, which was intuitive as they should both have same cation concentration and distribution. The neat and dedoped line-cuts were nominally identical with each other, and distinct from the exposed and redoped line cuts, with a suppression of the main scattering feature. This reflects a diminished electron density contrast between the PSS-rich and PEDOT-rich domains due to the minimal effect of protons in the cation-free neat film, and the decreased differential cation concentration between the domains in the dedoped samples, as cations displace holes in the PEDOT-rich domains.