Residual Solvent Effects on the Mechanical and Triboelectric Properties of Solution-Processed Polymer Films

Residual solvents are an often-overlooked factor that may influence the triboelectric performance of solution-processed polymer films. Here, the effect of solvent evaporation dynamics on triboelectric charging was investigated using poly(vinylidene fluoride) (PVDF)/N,N-dimethylformamide (DMF), ethylene-vinyl acetate (EVA)/toluene, and polyether block amide (PEBA)/chloroform systems. Residual solvent evolution was monitored by ATR-FTIR spectroscopy, while surface roughness, Kelvin-probe contact potential difference, and triboelectric charge density were measured as a function of drying time. All three systems exhibited time-dependent changes in triboelectric charge density after film deposition. The strongest effect was observed for PVDF/DMF, where decreasing DMF-related FTIR bands coincided with a substantial reduction in triboelectric charge. EVA/toluene and PEBA/chloroform films also showed drying-dependent changes despite limited or absent spectroscopic evidence of the residual solvent, indicating contributions from post-deposition film equilibration. The results demonstrate that triboelectric properties can evolve significantly after film formation and that measurements performed before complete equilibration may not reflect the intrinsic behaviour of the material. These findings identify drying history as a critical parameter in the characterization and comparison of triboelectric materials.