Ebrahim Abouzari-Lotf - Preparation and properties of new ortho-linked polyamide-imides bearing ether, sulfur, and trifluoromethyl linkages

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      Shockravi, A., Abouzari-Lotf, E., Javadi, A., Atabaki, F.   45 (5) 1599-1606

      Abstract: A CF 3-containing diamine,   2,2′-thiobis-[4-methyl(2-trifluoromethyl)4-aminophenoxy) phenyl   ether] (DA), was successfully synthesized from   2-2′-sulfide-bis-(4-methyl phenol) and   2-chloro-5-nitrobenzotrifluoride. The sulfur containing   diimide-diacid (DIDA) was prepared by condensation reaction of   diamine DA and trimellitic anhydride. A series of novel   organic-soluble polyamide-imides (PAIs) bearing flexible ether   and sulfide links, electron-withdrawing trifluoromethyl groups   and ortho-phenylene units were synthesized from DIDA, by direct   polycondensation with various aromatic diamines in   N-methyl-2-pyrrolidone using triphenyl phosphite and pyridine as   a condensing agent in the presence of dehydrating agent (LiCl).   The polyamide-imides were obtained in high yields and possessed   inherent viscosities in the range of 0.42-0.95 dL g -1. All of   the polymers were amorphous in nature, showed outstanding   solubility and could be easily dissolved in amide-type polar   aprotic solvents (e.g., N-methyl-2-pyrrolidone,   N,N-dimethylacetamide, and N,N-dimethylformamide) and even   dissolved in less polar solvents (e.g., pyridine and   tetrahydrofuran). They showed good thermal stability with glass   transition temperatures between 195-245 °C, 10% weight loss   temperatures in excess of 485 °C, and char yields more than 50%   at 700 °C in nitrogen atmosphere. Moreover, these PAIs possessed   low refractive indexes (n = 1.57-1.59) and low birefringence (Δ ≈   0.02) due to the trifluoromethyl pendent groups and thioether   bridged ortho-catenated aromatic rings that interrupt chain   packing and increase free volume. © 2009 Elsevier Ltd. All rights   reserved.

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