Extended Data Fig. 2: EDS with I-PDP.

Iodine-labelled small molecules are used to show the small-molecule distribution in a S2/NP blend. The structural and chemical information is collected using a high-angle annular dark-field set-up, so the contrast is reversed compared with the other TEM images shown in this work. The brightest pixels are those that scatter most strongly, so the nanoparticle-filled domains are lighter than the organic-only domains. The iodine map shows that I-PDP are distributed throughout all microdomains, despite the enthalpic driving force for them to segregate into the P4VP(PDP) domains. By comparison, the ZrO₂ nanoparticles are strictly partitioned into the P4VP(PDP) domains. This imaging technique does not differentiate between hydrogen-bonded and unbonded small molecules, so the P4VP(PDP) domains have an overall higher concentration of small molecules.