Solution-processable poly(ether imide)s (PEIs) with ureidopyrimidinone (UPy) end groups were prepared by incorporating monoisocyanato-6-methylisocytosine into amine terminated PEI oligomers. After functionalization with UPy end groups, PEI with a molecular weight as low as 8 kDa (8k-PEIUPy) can be solution-cast to form films. Tensile tests revealed that 8k-PEI-UPy had an outstanding Young's modulus higher than those of state-of-the-art high-molecular-weight commercial PEIs. The tensile strength, maximum elongation, and Young's modulus of 8k-PEI-UPy were 87.2 +/- 10.8 MPa, 3.10 +/- 0.39%, and (3.20 +/- 0.14) X 10(3) MPa, respectively. The discovery herein significantly advances the chemistry of high-temperature PEI resins. UPybased supramolecular chemistry is an effective and general strategy to achieve outstanding mechanical properties for PEI oligomers.