4-Phenylethynylphthalic anhydride (PEPA) is a phthalic anhydride derivative with a phenylethynyl substituent in the 4-position.PEPA is commonly used as a reactive capping agent for polyimide synthesis and aromatic oligo-polyimides. Fluorinated aromatic oligoimides terminated with a phenylethynyl substituent melt completely in the range of 250-350 °C to form a low viscosity liquid. The melt viscosity of oligoimides increases with increasing molecular weight. After thermal curing at 371 °C, the thermoset polyimide resins produced show good thermal and mechanical properties. They showed a high glass transition temperature (Tg) of 300 °C, a flexural strength of 135.5 MPa, a flexural modulus of 3.1 GPa, a tensile strength of 65.7 MPa, and an elongation at break of 3.9%.
