Structure of plasma‐deposited copolymer films prepared from acrylic acid and styrene: Part III sulfonation and electrochemical properties.

Acrylic acid‐styrene copolymer films were deposited plasma‐chemically more gently using the pulsed plasma mode instead of the continuous mode, with linear and some slightly branched chains and marginal crosslinking. Then, the styrene unit of copolymers was wet‐chemically sulfonated by chlorosulfuric acid. On exposure to air, the formed 4‐chlorosulfonic acid groups hydrolyze to sulfonic acid groups (–SO3H). Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and broadband dielectric spectroscopy were employed to characterize the composition, structure, functional groups, and electrochemical performance of the copolymers. A high concentration of sulfonic acid‐containing groups was obtained in the sulfonated polystyrene sample. The values of the DC conductivity σDC for the sulfonated sample of the acrylic acid and styrene copolymer are ca. five orders of magnitude higher than that of the not‐sulfonated copolymer materials. [ABSTRACT FROM AUTHOR]