A series of molecular-weight-controlled imide resins end-capped with phenylethynyl groups were prepared through the polycondensation of a mixture of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene and 1,3-bis(4-aminophenoxy)benzene with 4,4 0 -oxydiphthalic anhydride in the presence of 4-phenylethynylphthalic anhydride as an endcapping agent. The effects of the resin chemical structures and molecular weights on their melt processability and thermal properties were systematically investigated. The experimental results demonstrated that the molecular-weight-controlled imide resins exhibited not only meltability and melt stability but also low melt viscosity and high fluidability at temperatures lower than 2808C. The molecular-weight-controlled imide resins could be thermally cured at 3718C to yield thermoset polyimides by polymer chain extension and crosslinking. The neat thermoset polyimides showed excellent thermal stability, with an initial thermal decomposition temperature of more than 5008C and high glass-transition temperatures greater than 2908C, and good mechanical properties, with flexural strengths in the range of 140.1-163.6 MPa, flexural moduli of 3.0-3.6 GPa, tensile strengths of 60.7-93.8 MPa, and elongations at break as high as 14.7%.

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