Nanoconfinement‐Tailored <scp> g‐C ₃ N ₄ </scp> /Ethyl Cellulose Composite Films With Tunable Porosity for Acid‐Resistant Protective Barrier

ABSTRACT Ethyl cellulose (EC)‐based temporary protective coatings suffer from inherent structural instability and limited acid resistance. In this study, g‐C 3 N 4 /EC composite films with different nanofiller loadings (1–4 wt%) are prepared via phase‐inversion processing. Electrochemical impedance spectroscopy (EIS) demonstrates a 165% impedance increase (to 17.3 kΩ) at 4 wt% g‐C 3 N 4 incorporation, compared with the pure EC film. The increase in the impedance could be attributed to filler‐occupied pore channels and restricted polymer chain mobility. After 72‐h acid exposure (pH = 2), the composite films retain &gt; 10 kΩ impedance, confirming robust acid barrier. Gel permeation chromatography (GPC) and mechanistic analysis reveal that high‐concentration g‐C 3 N 4 (4 wt%) induces nanoconfinement effects, shifting acid‐driven degradation from chain scission to crosslinking‐dominated 3D network formation. This structural evolution is corroborated by SEM, showing pore fusion at the filler content of 6 wt%. The tunable porosity and acid‐triggered self‐reinforcement mechanism establish an easy method for sustainable, removable protective coatings in precision electronics.