Novel Aromatic Polyimides Derived from 5′-t-Butyl-2′-pivaloylimino-3,4,3′′,4′′-m-terphenyltetracarboxylic Dianhydride with Potential Application on Gas Separation Processes

Abstract

A new family of polyimides having two bulky groups in the central ring of a m-terphenyl moiety has been obtained. These polyimides have been synthesized by reaction of four commercial diamines with the electrophilic monomer, 5′-t-butyl-2′-pivaloylimino-3,4,3′′,4′′-m-terphenyltetracarboxylic acid dianhydride (PTPDA). This monomer has been obtained by a modern C−H-activated arylation method with good yield and purity. The attained polymers showed Tg values ranging from 300 to 430 °C, thermal stability >500 °C, and excellent solubility in a broad range of solvents, including tetrahydrofuran. Despite having an amide group, uptake of water was low and comparable to that of classical aromatic polyimides. Mechanical properties of polymer films were good enough to permit the use of these polyimides on gas separation applications at high pressures. Films obtained by casting offered a good balance of permeability and permselectivity with values close to the Robeson upper-bound, in particular for the O2/N2 gas pair.