Synthesis and Properties of Novel Meltable Fluorinated Aromatic Oligoimides Endcapped with 4-Phenylethynylphthalic Anhydride

A series of phenylethynyl-endcapped fluorinated aromatic oligoimides with calculated molecular weights of 1250-10000 were prepared by thermal polycondensation of an aromatic dianhydride, 4,4'-oxydiphthalic anhydride (ODPA), with aromatic diamine mixtures of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (1,4,4-6FAPB) and 3,4'-oxydianiline (3,4'-ODA) in the presence of 4-phenylethynylphthalic anhydride (PEPA) as reactive endcapping agent. Effects of chemical compositions and molecular weights of the aromatic oligoimides on their meltability as well as the thermal and mechanical properties of the thermal-cured polyimide resins were systematically investigated. The phenylethynyl-endcapped fluorinated aromatic oligoimides could be completely melted in the temperature range of 250-350 degrees C to give low viscosity fluids. The melt viscosity of the oligoimide increased with increasing molecular weight. After thermally curing at 371 degrees C, the thermoset polyimide resins produced showed good combination of thermal and mechanical properties. For example, the glass transition temperature (T-g) as high as 300 degrees C by differential scanning calorimetry, flexural strengths of > 135.5 MPa, flexural moduli of > 3.1 GPa, tensile strength of > 65.7 MPa and elongation at break of > 3.9% were obtained.