Spontaneous polarization in chemical vapor-deposited polymer films creates large electric fields.

Abstract

Controlled surface potentials in permanently polarized polymer films are of increasing interest for electronics, sensing, and biomedical devices. Conventional polymer films require external electric fields or postdeposition treatments, limiting precision and scalability. Here, we report a spontaneous polarization in polymer thin films polymerized through initiated chemical vapor deposition (iCVD). Surface potentials emerge spontaneously during film growth, scale linearly with film thickness, and remain stable under ambient conditions. Their magnitude is tunable through deposition parameters, and polymerization initiator choice determines the polarity. The solvent-free, single-step iCVD process enables mechanically robust, uniform coatings on complex geometries and large areas. Our findings establish a simple, versatile route to intrinsically polarized polymer films without postprocessing, opening new opportunities for direct integration of electric fields into functional devices or surface-driven processes at the nanoscale.