Synthesis and characterization of new organosoluble polyimides based on flexible diamine

The new five benzene rings-containing diamine, alpha,alpha ' -bis[3,5-dimet hyl-4-(4-aminophenoxy)phenyl]-1,4-diisopropylbenzene (BDAPD) was prepared b y the aromatic nucleophilic substitution of alpha,alpha ' -bis(4-hydroxy-3, 5-dimethylphenyl)-1,4-diisopropylbenzene with 1-chloro-4-nitrobenzene, and subsequent hydrogenation of the intermediate dinitro. The diamine was react ed with various aromatic dianhydrides to prepare a series of new polyimides (IPs) via the poly(amic acid) precursors and thermal or chemical imidizati on. The polyimides were produced with inherent viscosities of 0.60-0.85 dl g(-1) by chemical imidization. All the poly(amic acid)s films could be obta ined by solution-cast from N,N-dimethylacetamide (DMAc) solutions and therm ally converted into transparent, flexible, and tough polyimide films. The w ide-angle X-ray diffraction diagrams revealed that all the polyimides showe d amorphous character. All of the polyimides, except PI-1, showed excellent solubility in a variety of solvents such as N-methyl-2-pyrrolidinone, DMAc , N,N-dimethylformade, dimethyl sulfoxide, pyridine, cyclohexanone: and tet rahydrofuran. Such polyimides had better solubility than those containing o nly one isopropylidene unit or a hexafluoroisopropylidene linkage in the re peating unit of polyimide backbone. These polyimides had glass transition t emperatures (T-g) between 241 and 270 degreesC, which were higher than the T-g value of Ultem 1000 (215 degreesC). The thermogravimetric analyses demo nstrated that almost all of the polymers were stable up to 450 degreesC, an d the 10% weight loss temperatures were recorded in the range 466-488 degre esC in air atmosphere. (C) 2001 Elsevier Science Ltd. All rights reserved.