Hexafluoroisopropylidene bis phthalic

Polyisoimides have better solubihty and improved melt flow characteristics [59, 60]. The isoimide groups rearrange to imides on heating above 300 °C. Better processability is also achieved by substituting hexafluoroisopropylidene-bis(phthalic anhydride) (6FDA) for BTDA, Thermid FA-700 [61-63]. 

The thermo-oxidative stability of this first generation material was improved by the introduction of a second generation resin [43]. Initially the BTDE was replaced by the dimethyl ester of 4,4 -(hexafluoroisopropylidene)-bis(phthalic acid) (HFDE), which significantly improved the thermo-oxidative stability, but the initial mechanical properties at 316°C were inferior to PMR-15. This was overcome by replacing the MDA with p-phenylenediamine (PPDA). Hence, the monomers used for the second generation resin comprised the dimethyl ester of 4,4 -(hexafluoroisopropylidene)-bis(phthalic acid) (HFDE), /7-phenylenediamine (PPDA) and monomethyl ester of 5-nobornene-2,3-dicarboxylic acid (NE), in the molar ratio n n- -l 2 for HFDE PPDA NE. When =1.67, the formulated... 

Materials The materials in this work includ< a lyotropic polyamide (PBTA) composed of terephthaloyl dichloride and 2,2 -dimethyI-4,4-diamino-biphenyl two amorphous polyimides respectively con sting of 3,3 4,4-benzophenone tetracarboxylic dianhydride (BTDA) and 2,3,5,6-tetrameth -p-phenylene diamine (TMPD), as well as 4,4 -(hexafluoroisopropylidene)>bis(phthalic anhydride) (6FDA) and 2,2-dimethyl-4,4-diamino-biphenyl (DMDB) and the block copolymers composed of PBTA and those two polyimides with various compositions. Ilie PBTA/PI block copolymers and the corresponding homopolymers were prepared according to our previous work(79). 

Poly(imide-siloxane)s copolymers have been prepared by the reaction of 4,4 -(4,4 -isopropylidene-diphenoxy)bis(phthalic anhydride), 4,4 -oxydiani-line, and an amino-propyl terminated poly(dimethyl-siloxane) [12]. The polymers exhibit a good solubility in various organic solvents. In addition, 4,4 -(hexafluoroisopropylidene)diphthalic anhydride was used as hard block segment [84]. 

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