Phenylethynyl- and naphthylethynyl-terminated hyperbranched polyimides with low melt viscosity

Abstract

In the past decades, 4-phenylethynyl phthalic anhydride has been the most commonly used endcapper for polyimide (PI). A series of different groups of terminated hyperbranched PIs (HBPIs) were synthesized from 1,3,5-tris(2-trifluoromethyl-4-aminophenoxy)benzene, bis[4-(3,4-dicarboxyphenoxy)phenyl]ether dianhydride, and 4-phenylethynylphthalic anhydride or 4-(1-naphthylethynyl)phthalic anhydride. The glass transition temperatures ( Tgs) of the polymers varied from 166°C to 193°C. The 5% weight loss temperatures of polymers were in the range of 548 to 571°C and those of the endcapped HBPIs increased to the range of 600 to 601°C after curing. The PIs exhibited rather low melt viscosity at processing temperature and the complex viscosity increased continuously with the temperature increase. Because there is a large temperature difference between the Tg and cross-linking exothermic temperature, HBPIs provided a wide processing window.