Ethylene removal by sorption from polymeric crystalline frameworks

Abstract

The uptake and diffusivity of ethylene in amorphous and semicrystalline s-PS (syndiotactic polystyrene) films presenting different crystalline phases and different crystalline-phase orientations have been studied by gravimetric and Fourier transform infrared measurements. High solubility and low diffusivity of ethylene have been observed for the nanoporous host δ phase of s-PS, due to the formation of a co-crystalline phase, where ethylene molecules are oriented nearly perpendicular to the polymer helices. In addition, ethylene diffusivity can be minimized by suitable (002) uniplanar orientation of the host crystalline phase, i.e. by placing the crystalline polymer helices perpendicular to the film surface. Ethylene-desorption measurements conducted at different temperatures have allowed us to evaluate activation energies relative to ethylene diffusion. The reported results suggest that this cheap, robust and easy-to-process polymeric material is suitable for (also for repeated use) food packaging requiring ethylene removal.