Syntheses and properties of novel polyimides derived from 2-(4-aminophenyl)-5-aminopyrimidine

2-(4-Aminophenyl)-5-aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo- and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97-4.38 dL/g (c = 0.5 g/dL, in DMAc, 30 degrees C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307-434 degrees C and the 10% weight loss temperature is in the range of 556-609 degrees C under air. The polyimide films possess strength at break in the range of 185-271 MPa, elongations at break in the range of 6.8-51%, and tensile modulus in the range of 3.5-6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance.

Gas permeability and permselectivity of polyimides prepared from phenylenediamines with methyl substitution at the ortho position

Polyimides were prepared from diamines: 2,4,6-trimethyl-1,3-phenylenediamine (3MPDA) and 2,3,4,5-tetramethyl-1,4-phenylenediamine (4MPDA). 1,4-Bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3'-4,4'-diphenylsulphone tetracarboxylic dianhydride (SO(2)PDA), 3,3',4,4'-diphenylsulphide tetracarboxylic dianhydride (SPDA), pyromellitic dianhydride (PMDA), and 2,2'-bis(3,4-dicarboxyphenyl)hexa-fluoroisopropane dianhydride (6FDA) were used as dianhydride. The gas permeabilities of H-2, O-2 and N-2 through the polyimides were measured at temperatures from 30 degrees C to 90 degrees C. The results show that as methyl and trifluoromethyl substitution groups densities increase from 7.73 x 10(-3) molcm(-3) to 13.50 x 10(-3)molcm(-3), the peameability of H-2 increases 10-fold at 60% loss of permselectivity of H-2/N-2 however, the permeability of O-2 increases 20-fold at 20% loss of permselectivity of O-2/N-2. For O-2/N-2 separation, PMDA-3MPDA has similar performance to 6FDA-3MPDA and 6FDA-4MPDA; all have higher permeabilities for O-2 than normal polyimides, and the P(O-2)/alpha(O-2/N-2) trade-off relationships lie on the upper bound line for polymers. (C) 1999 Society of Chemical Industry.

Synthesis and miscibility studies of rodlike flexible polyimide molecular composites via para-para linked aromatic poly(amic ester) precursors

Para-para linked aromatic poly(amic ester) precursors of rodlike polyimide (PI) BPDA-PDA and polyetherimide (PEI) HQDPA-ODA were synthesized. The para-para linked poly(amic ester)s were employed in this work to obtain, in theory, full-imidized polyimides. The two precursors were mixed by dissolving them in N, N'-dimethyl acetamide and subsequently coagulating in methanol. After thermal imidization, the miscibility behaviour of the resulting composites has been studied by means of dynamic mechanical analysis (d.m.a.) and differential scanning calorimetry (d.s.c.). The composites show a single glass transition temperature (T-g) at both d.m.a. and d.s.c. in which the T-g increases with increasing PI content. These Tg values are reproducible in repeated heating cycles, suggesting the true miscibility of the blends. (C) 1997 Elsevier Science Ltd.

Gas separation properties of aromatic polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 3,5-diaminobenzic acid or its esters

The gas transport properties of a series polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) with 1,3-phenylenediamine or 3,5-diaminobenzic acid (DBA) or its esters are reported. The effects of carboxylic group (-COOH) and carboxylic ether groups (-COOR), at five positions of 1,3-phenylenediamine moiety, on H-2, CO2, O-2, and N-2 permeability, diffusivity, and solubility of the polyetherimides were investigated. The gas permeability, diffusion, and solubility coefficients of the polyetherimides containing COOR are bigger than those of HQDPA-PDA, but the ideal separation factors and ideal diffusivity selectivity factors are much smaller than that of HQDPA-PDA because COOR decreases chain segmental packing efficiency and increases chain segmental mobility. The permeability coefficients of HQDPA-DBA to H-2, CO2, and O-2 are bigger than those of HQDPA-PDA; the ideal separation factors for gas pairs H-2/N-2, CO2/N-2, and O-2/N-2 are also much bigger than those of HQDPA-PDA. Both the diffusion coefficients of CO2 and O-2 and the ideal diffusivity selectivity factors for CO2/N-2 and O-2/N-2 are bigger than those of HQDPA-PDA because COOH decreases both chain segmental packing efficiency and chain segmental mobility. The copolyimides, which were prepared from 3,5-diaminobenzic acid and 3,5-diaminobenzic esters, have both high permeability and high permselectivity. (C) 1997 John Wiley & Sons, Inc.