Synthesis and Gas Permeation Properties of Star-like Poly(ethylene oxide)s Using Hyperbranched Polyimide as Central Core

Abstract

A series of star-like poly(ethylene oxide)s were synthesized using anhydride-terminated hyperbranched polyimides as the central cores and poly(ethylene oxide)s (PEOs) as the linear arms. Their physical and gas permeation properties were investigated in comparison with those of PEO segmented block copolyimides (PEO-PIs). The solubility of star-like PEOs was affected by the terminal groups. The amine-terminated star-like PEOs displayed better solubility property than the methoxy- and acetamido-terminated ones. The DSC and dynamic mechanical spectroscopy suggested the morphology of star-like PEOs was different from that of PEO-PIs. The thermo-mechanical property of amine-terminated star-like PEOs was significantly improved by cross-linking with ethylene glycol diglycidyl ether. The star-like PEO membranes were much more permeable to CO2 than to N2 and even to H2. However, their CO2 separation performance was slightly lower than that of PEO-PIs, probably due to the difference in the morphology. The AgBF4-doped star-like PEO membrane with a loading of 40 wt% (corresponding to 67 wt% in PEO matrix) showed a very high ideal selectivity of C2H4/C2H6 of more than 100 with a low ethylene permeability of 1.5×10−10 cm3 (STP) cm−1 s−1 cm Hg−1 in single-component permeation at 2 atm and 308 K. However, the permselectivity decreased down to 14 in mixed gas permeation. The permeation behavior was discussed based on the solubility and diffusivity.