In-situ polymerized Pebax^®/polydopamine blend membranes with high CO₂/N₂ selectivity

Abstract

The objective of this work was to produce Pebax^®/polydopamine (PDA) blends and apply these blends to produce membranes for gas separation. Flat sheet membranes were tested for gas permeation, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), wide angle x-ray diffraction (WAXD), scanning electron microscopy (SEM) and fourier transformed infrared spectroscopy (FTIR). The results show an optimal concentration of dopamine hydrochloride that produces the best results (𝛼=100, P=114 Barrer). DSC and WAXD results indicate that polydopamine influences the crystallization of Pebax^®, reducing the melting and crystallization temperatures of PA blocks and increasing the melting temperature of PEO blocks. The incorporation of PDA decreases gas permeability and increases gas selectivity. The decrease in permeability indicates that the presence of polydopamine reduces the diffusion coefficient of Pebax^® by reducing the segmental mobility of PEO blocks and possibly the fraction free volume. Compared to the trade-off, Pebax^®/PDA membranes surpasses the upperbound for CO₂/N₂ separation.

Keywords:
Pebax; polydopamine (PDA); in-situ polymerization; CO₂ separation; polymer blends