Synthesis And Properties Of New Series Of Asymmetry Diamines And Correspond Ing Soluble Polyimides

Aromatic polyimides possess excellent thermal and mechanical, electrical, and chemical properties. Therefore, they are being used in many applications such as electrics, coatings, composite material, and membranes. However, the commercial use of these materials is often limited because of their poor solubility, and high softening or melting temperatures. To overcome these problems, more and more attempts have been focused on the preparation of novel polyimides with improved properties.This paper summarizes the structural characteristics of polyimides with excellent properties, and analyzed the contributions of several structural modification methods to each aspect of polyimide properties. Four novel aromatic diamines were designed and prepared based on the viewpoint of molecular design, which structures were confirmed by elementary analysis, FT-IR, NMR and MS. Derived from the resulted diamines and dianhydrides such as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA),4,4'-Oxydiphthalic anhydride (ODPA),3,3',4,4'-benzophenonete-Tracarboxylic dianhydride (BTDA) and Pyromellitic dianhydride (PMDA), four series of novel polyimides were successfully synthesized. The polymer constructions were confirmed by elementary analysis, FT-IR and 1H-NMR. Their solubility, thermal property, mechanical property, aggregate structures, and dielectric property were investigated and discussed.A series of new polyimides were synthesized from an unsymmetrical aromatic diamine, 5-amino-2-(4-aminophenoxy)-pyridine with various commercially available aromatic dianhydrides. The resulting polyimides exhibited excellent solubility in polar solvents, such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidinone. Meanwhile, we detected the influence of resonance structure of hydroxypyridine to lactam to the synthesis of pyridyl ether linkage monomer.A kinds of aromatic, unsymmetrical diamines with ether-ketone group, 4-amino-4'-(4-amino-2-trifluoromethylphenoxy)-benzophenone, were successfully synthesized with two different synthetic routes. Then, they were polymerized with 4,4'-oxydiphthalic anhydride,3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 2,2'-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride to form a series of fluorinated polyimides via a conventional two-step thermal or chemical imidization method. The resulting polyimides were characterized by measuring their solubility, viscosity, mechanical properties, IR-FT, and thermal analysis. The results showed that the polyimides had inherent viscosities of 0.48-0.68 dL/g and were easily dissolved in bipolarity solvents and common, low-boiling point solvents. Meanwhile, the resulting strong and flexible polyimide films exhibited excellent thermal stability, e.g. decomposition temperatures (at 10%weight loss) are above 575℃and glass-transition temperatures in the range of 218-242℃. The polymer films also showed outstanding mechanical properties, such as tensile strengths of 86.5-132.8 MPa, elongations at break of 8-14%, and initial moduli of 1.32-1.97 GPa. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced applications.Two kinds of novel aromatic, unsymmetrical diamines with ether-ketone group, 3-amino-4'-(4-amino-2-trifluoromethylphenoxy)-benzophenone and 3-amino-4'-(4-aminophenoxy)-benzophenone, was successfully synthesized by two different synthetical routes and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4'-oxydiphthalic anhydride,3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 2,2'-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride, via a conventional two-step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, mechanical properties tests, IR-FT, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.54-0.77 dL/g and were easily dissolved in both polar, aprotic solvents and common, low-boilingpoint solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 10%weight loss) above 573℃and glass-transition temperatures in the range of 222-251℃. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 86.5-121.6 MPa, elongations at break of 9-16%, and initial moduli of 1.26-1.97 GPa. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced applications.A new aromatic ether diamine, bis[3-(4-amino-2-trifluoromethylphenoxy) phenyl] ether, was successfully synthesized via nucleophilic substitution reaction of 3,3'-oxydiphenol and 2-chloro-5-nitrotrifluoromethylbenzene, followed by a catalytic reduction. A series of new polyimides were synthesized from the diamine with various commercially available aromatic dianhydrides via a conventional two-stage process, i.e. ring-opening polyaddition forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides. The resulting polyimides exhibited good solubility in polar solvents, such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidinone, and common solvents such as chloroform, tetrahydrofuran upon heating, and possessed the inherent viscosities of 0.51-0.68 dL/g. The resulting strong and flexible films exhibited excellent thermal stability with the temperature at 10%weight loss is above 502℃and the glass transition temperature in the range of 191-232℃. The polyimides also were found to possess high optical transparency.