Phenylethynyl-endcapped oligomides with low melt viscosities and high Tgs: effects of the molecular weights

Abstract

Phenylethynyl-endcapped imideoligomers (oligomides) with low melt viscosities and high glass transition temperatures ( Tg) were prepared by the high temperature polycondensation of 2,3,3′,4′-biphenyltetracarboxcylic anhydride (a-BPDA), 4,4′-methylenebis(2,6-dimethylaniline) (MBDA) and 4-phenylethynyl-phthalic anhydride (4-PEPA). Experimental results indicated that the oligomides were mixtures of biphenylethynyl-endcapped imide oligomers with different degrees of polymerization (DP = 0, 1, 2, 3, 4), corresponding to the molecular weights ( Mn) of 737 to 2787 determined by MALDI-TOF. The melt viscosities of the oligomide were reduced by lowering the calculated molecular weight (Calc’d Mn). The thermally cured polyimide neat resins showed glass transition temperatures ( Tg) of > 400 °C and 5% weight loss temperature ( T5) of > 499 °C. It was also found that the mechanical properties of the thermally cured polyimide neat resins were dependent on the Calc’d Mn values of the oligomide, and improved gradually with increasing Calc’d Mn.