Engineering a hyperbranched polyimide membrane for shape memory and CO2 capture

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 m(2) g(-1)), mesoporous characteristics (3-5 nm) and narrow pore size distribution, which endow them with preferable CO2 capture (up to 36.93 cm(3) 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.