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 T, values ranging from 300 to 430 degrees C, thermal stability > 500 degrees 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 oil gas separation applications Ell high pressures. Films obtained by casting offered it good balance of permeability and permselectivity with values close to the Robeson upper-bound, in particular for the O-2/N-2 gas pair.