A series of diamine monomers, i.e., 2,2‘-bis{4-[3,4,5-tris(n-alkan-1-yloxy)benzoate]}-4,4‘-biphenyldiamines containing multiple alkyl side chains, were synthesized in which the length of the alkyl side chains was varied from 5 to 18 carbon atoms. Polyimides were prepared from the diamines and pyromellitic dianhydride (PMDA), 3,3‘4,4‘-biphenyltetracarboxylic dianhydride (BPDA), 2,2‘-dibromo-4,4‘,5,5‘-biphenyltetracarboxylic dianhydride (DBBPDA), and 2,2‘-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), respectively, using a one-step method in 1,2-dichlorobenzene or 1-chloronaphthalene. Most of the polymers had good solubility in chlorinated solvents. Several copolyimides were prepared: BPDA, 2,2‘-bis(trifluoromethyl)benzidine (PFMB), and C14 and C16 diamines. The solubility of copolyimides was dramatically affected by different monomer addition sequences. The high-molecular-weight polyimides could be solution cast into flexible, tough films except for those based on PMDA. The side chains that...