Synthesis of novel aromatic polyamides containing both sulfone linkages and cardo groups by a recyclable palladium-catalyzed carbonylation and condensation polymerization

A series of novel aromatic polyamides containing both sulfone linkages and cardo groups were synthesized via a heterogeneous palladium-catalyzed carbonylation and condensation reaction of aromatic diiodides bearing ether sulfone linkages, carbon monoxide, and aromatic diamines with cardo groups. Polycondensation reaction proceeded smoothly under 1 atm of CO at 120 °C in N,N-dimethylacetamide (DMAc) by using a bidentate phosphine ligand-modified magnetic nanoparticles-anchored palladium complex [2P-Fe3O4@SiO2-PdCl2] as a recyclable catalyst with 1,8-diazabicycle[5,4,0]-7-undecene (DBU) as a base, furnishing cardo poly(ether sulfone amide)s with inherent viscosities between 0.70 and 0.77 dL/g. The resulting polyamides could be readily dissolved in polar aprotic organic solvents and even dissolved in less polar pyridine and tetrahydrofuran at room temperature and could be easily converted into flexible, transparent, and tough films via casting from their solutions in DMAc. These polymers exhibited excellent thermal stability with the glass transition temperatures between 241 and 283 °C and the temperatures at 5% weight loss ranging from 438 to 475 °C in an atmosphere of nitrogen. The polyamide films displayed good mechanical behavior with tensile strengths of 78.8–84.4 MPa, tensile moduli of 2.08–2.57 GPa, and elongations at breakage of 10.2–12.5%, and optically high transparency with cut-off wavelengths in the range of 338–368 nm.