Rapid SANS Investigation of PVP/cPIM-1 to Complete Structural Characterization for PhD Thesis

High-temperature proton exchange membrane fuel cells offer high efficiency and fuel flexibility but suffer from phosphoric acid (PA) leaching in PA-doped membranes, limiting durability. To address this, composite membranes based on carboxyl-functionalized polymers of intrinsic microporosity (cPIM-1) and polyvinylpyrrolidone (PVP) were developed. The microporous structure of cPIM-1 provides capillary effect, while hydrogen bonding stabilizes PA, reducing acid loss. Small-angle neutron scattering (SANS) experiments were conducted at ISIS under dry and PA-doped conditions, including at 150 degrees Celsius to simulate operating conditions. Results show that PVP/cPIM-1 maintain stable and confined PA clusters, while PVP/PES exhibit phase separation and cluster growth upon heating. Fitting analysis indicates that acid clusters in PVP/cPIM-1 shrink from 1.0 1.5 nm at room temperature to 0.5 1.0 nm at 150 degrees Celsius, while clusters in PVP/PES grow from 2.0 to 3.5 nm. A new peak appeared at 150 degrees Celsius in PVP/cPIM-1, possibly indicating ionic structures between PA and the polymer (anchoring effect). Due to limited beamtime, further investigation of this feature remains incomplete. This structural insight is critical for understanding acid polymer interactions in PVP/cPIM-1 membranes and for developing cPIM-1 as an ionomer binder. Completing this analysis is a key part of Xiaochen Yang's doctoral research, directly supporting the conclusions of his thesis.