Improvement in the CO2 Permeation Properties of High-Molecular-Weight Poly(ethylene oxide): Use of Amine-Branched Poly(amidoamine) Dendrimer

High-molecular-weight (e.g., 1000000 g mol–1) poly(ethylene oxide) (PEO) is a candidate polymer for CO2 separation membranes because of its low cost and high CO2 affinity. However, high-molecular-weight PEO membranes contain large crystallites, which cause structural defects. Here, we report defect-free, high-molecular-weight PEO membranes with good CO2 separation performance prepared using amine-branched poly(amidoamine) (PAMAM) dendrimers. PAMAM, obtained by two-step addition polymerization, acts as a filler in the all-polymer membranes. The intermolecular hydrogen bonding between the PEO and filler yields transparent, uniform membranes with improved mechanical strength. The primary amines in PAMAM facilitate CO2 transport by increasing CO2 solubility in the membrane. The PEO/PAMAM membranes show ∼6 times greater CO2/N2 selectivity than that of neat PEO. The PEO/PAMAM membrane with 2.5 wt % PAMAM loading has a CO2 permeability of 32.3 barrer and a CO2/N2 selectivity of 42, representing the best gas separation performance of free-standing high-molecular-weight PEO-based membranes to date.