Phenylethynyl-endcapped imideoligomers (oligomide) with low melt viscosities and high glasstransition temperatures (T_g) were prepared by the high temperature polycondensation of 2,3,3′,4′-biphenyltetracarboxcylic anhydride (α-BPDA), 4,4'-methylenebis(2,6-dimethylaniline) (MBDA)and 4-phenylethynyl -phthalic anhydride (4-PEPA). Experimental results indicated that theoligomides were mixtures of biphenylethynyl-endcapped imide oligomers with different degreeof polymerization (DP = 0, 1, 2, 3, 4), corresponding to the molecular weights (M_n) of 737 to2787 determined by MALDI-TOF. The melt viscosities of the oligomide were reduced bylowering the calculated molecular weight (Calc'd M_n). The thermally cured polyimide neat resinsshowed glass transition temperature (T_g) of >400 °C and 5% weight loss temperature (T_5) of>499 °C. It was also found that the mechanical properties of the thermally cured polyimide neatresins were depended on the Calc'd M_n values of the oligomide, and improved gradually withincreasing Calc'd M_n.
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