Engineering a hyperbranched polyimide membrane for shape memory and CO2 capture

Abstract

The combination of shape memory with other new-fashioned functions will facilitate great potential in the development of shape memory materials. Demonstrated here is a multifunctional polymer based on hyperbranched polyimides (HBPIs) that integrates shape memory into a gas capture membrane. The new kind of shape memory gas capture HBPIs were prepared by branching conventional thermoplastic polyimides via a two-step method with 2,4,6-triaminopyrimidine (TAP) as the branched center. The optimized HBPIs exhibit good shape-memory properties with shape fixity above 98% and recovery values above 82%. Moreover, they show large Brunauer–Emmett–Teller (BET) surface areas (218–387 m² g⁻¹), mesoporous characteristics (3–5 nm) and narrow pore size distribution, which endow them with preferable CO₂ capture (up to 36.93 cm³ g⁻¹) and selectivity (up to 66.3). The comprehensive properties, especially the shape recovery ratio and CO₂ uptake, of the HBPIs can be effectively controlled by adjusting the degree of branching (DB) or the content of the rigid heterocyclic diamine, 5-amino-2-(4-aminobenzene) benzoxazole (BOA). Our multifunctional shape memory polymer (SMP) may expand the application field of shape memory and accelerate the development of SMPs.