科研之友
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摘要
Two novel fluorinated diimide-diacid monomers, [2,2'44,4'-(4'-chloro-3'-(trifluoromethyl)biphenyl-2,5-diy1)bis(oxy)bis(3-(trifluoromethyl)-4,1-phenylene))bis(1,3-dioxoisoindoline-5-car- boxylic acid)] (III) and [2,2'-(4,4'-(3',5'-bis(trifluoromethyl)bipheny1-2,5-diy1)bis(oxy)bis(3-(trifluoromethyl)-4,1-phe-nylene))bis(1,3-dioxoisoindoline-5-carboxylic acid)] (IV), were respectively designed and synthesized viathe reactions between the diamine (I or II) and two molar equivalents of trimellitic anhydride. Based on these two diimide-diacids, two families of novel poly(amide-imide)s (PAls) (Ilia-Ille and IVa-IVe) bearing different trifluoromethyl groups were prepared by directly polymerizing diimide-diacids with a series of aromatic diamines (a-e). All of the PAls exhibited high glass transition temperatures (T(g)s, 236-268 degrees C), excellent thermal stability (only 5% weight loss at 493-542 degrees C under nitrogen) and good solubility in various organic solvents since the bulky pendant groups were introduced. The cast films of these PAls (thickness = 80-90 mu m) had excellent optical transparency (70-83% at 450 nm, 85-87% at 550 nm and 88-89% at 800 nm) and low dielectric constants (2.62-2.92 at 1 MHz). In addition, the spin-coated films of these PAls presented very low birefringence values the minimum of which was 0.0073 at 650 nm. These spin-coated films also exhibited very weak absorption at the near-infrared communication wavelengths of 1310 and 1550 nm.
