A series of aliphatic–aromatic polyimides have been synthesized. These polyimides were prepared by high-temperature polycondensation of the aliphatic diamines: 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane and 4,4′-methylenebis(2,6-dimethylaniline) with 1,2,3,4-cyclopentanetetracarboxylic dianhydride. Various ratios of diamines (aromatic:aliphatic) have been applied for preparation of copolyimides. Polycondensation proceeded at 190 °C and produced copolyimides with reduced viscosities up to 0.92 dl/g. The polyimides were soluble in a wide range of organic, common solvents and showed high-thermal stability. In most cases these polymers formed flexible films which presented excellent transparency.
Optical transmission of a series of aliphatic–aromatic co-polyimides have been investigated in the range 200–3000 nm. The short wavelength edge of transmission depends on the ratios of diamines (aliphatic to aromatic) and on the type of aliphatic diamine. To obtain the optical parameters the approach proposed by Tauc for amorphous semiconductors has been used, because of the similarity of the absorption edges. The values of pseudogaps were found from 1.01 to above 4 eV, while the Urbach energy changed in the range 75–800 meV. All determined parameters have been found to be related to the influence of the polymer chain structure.
A series of copolymers from 3,3′,4,4′-benzophenonetetracarboxylic di-anhydride and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and two diamines, 4,4′-diaminodiphenylether and 3,5-diaminobenzoic acid, were synthesized. The influence of various ratios of diamines on the properties of polymers were investigated. A preliminary study on the potential of using the carboxylic acid group for substitution was carried out.
A series of polymers from dietherdianhydrides of arylene-di(benzene-5-ether-1,2-dicarboxylic) anhydride type and tetraamines: 3,3′-diaminobenzidine and 3,3′,4,4′-tetraaminodiphenyl ether were synthesized using high and low temperature polycondensation. The polymers had a semiladder structure. The influence of the monomer structure on the polymer properties has been investigated.
