Synthesis, characterization and gas permeation properties of anthracene maleimide-based polymers of intrinsic microporosity†
A series of new monomers containing dialkyl anthracene maleimide derivatives [4a,b(I–V)], which can be used as a precursor of a polymer of intrinsic microporosity (PIM) has been synthesized and characterized successfully. The homopolymers prepared via polycondensation with 2,3,5,6,-tetrafluoroterephthalonitrile (TFTPN) and their copolymers in combination with 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) were characterized by SEC, FT-IR, TGA, 1H-NMR, BET-surface area and gas transport properties. Compared to polymers derived from 4a(I–V) monomers, the homopolymers and copolymers obtained from 4b(I–V) show improved solubility in common organic solvents and have high average molecular weight. Therefore they are able to form robust and transparent films. The gas transport properties of homopolymers and copolymers of 4b(I–V) show enhanced selectivity compared to PIM-1 for gas pairs such as O2/N2, CO2/N2 and CO2/CH4, followed by a slight decrease in permeability. The introduction of anthracene maleimide units (especially 4bIII) in the copolymer leads to more efficient chain packing and gives the copolymer a similar pore width distribution as PIM-1. As a consequence, the introduction of anthracene maleimide enhanced the CO2 selectivity of copolymers, compared to previously reported film forming polymers. Therefore, these polymers might be useful for gas separations relying on CO2 selectivity.