Characterization Of Aromatic Polyimides Research Articles

Synthesis and characterization of aromatic polyimides containing tetraphenylfuran-thiazole moiety

2,5-Bis(4-(2-aminothiazole) phenyl)-3,4-diphenyl furan (BATPDF), well prepared in four steps. Novel aromatic polyimides containing tetraphenylfuran-thiazole unit were synthesized via a two-step thermal imidization derived from BATPDF with various commercially available dianhydrides such as pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydi (phthalic anhydride) (ODPA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). The resulting aromatic PIs were obtained in high yields and moderate inherent viscosities in the range of 0.42–0.48 dL g−1 and were practically amorphous as shown by the X-ray diffraction studies. All the polyimides exhibited excellent solubility in solvents, such as DMAc, NMP, m-cresol and pyridine on heating. PIs showed high glass transition temperatures between 238 and 252 °C. TG of the PIs indicated a 10% mass loss (T10%) in the temperature range of 518–609 °C and char yields at 900 °C under nitrogen atmosphere in the range of 58–65% depending on the dianhydrides monomer used for the synthesis PIs. The structure–property correlation between these polyimides was studied. In view of these polymer’s potential applications as thermally stable aerospace, optoelectronics and microelectronics device.

Comparative studies of polyimides with covalently bonded azo-dyes with their supramolecular analoges: Thermo-optical and photoinduced properties

The paper describes the synthesis and characterization of aromatic polyimides with azopyridine derivatives covalently attached as a side-chain and their supramolecular analoges based on the hydrogen bonds. Moreover, azopolymers differ in the chemical structure of the polymer backbone and the content of the chromophore. Azo-functionalized polymers were obtained by a two-step synthetic approach. This includes the preparation of a precursor with pendant hydroxyl groups followed by the covalent attachment of the chromophore, that is, 4-[4-(6-hydroxyhexyloxy)phenylazo]pyridine to the polyimide backbone. The degree of functionalization of the polymers was estimated by the UV–Vis spectroscopy. Supramolecular films were built on the basis of the hydrogen bonds between the hydroxyl groups of the polymer and azopyridine derivatives, that is, 4-(4-hydroxyphenylazo)pyridine and 4-[4-(6-hydroxyhexyloxy)phenylazo]pyridine. The polymers were characterized and evaluated by FTIR, 1H NMR, X-ray, UV–Vis, DSC and TGA methods.The synthesized precursor polymers revealed the glass transition temperature (Tg) in the range of 254–366°C, whereas azopolymers and supramolecular systems exhibited lower Tg within the ranges 129–153°C and 53–171°C, respectively. The polymers were easily soluble in common organic solvents enabling to obtain films of a good optical quality. The light-induced optical anisotropy was studied with the help of the holographic recording. The polymer films were investigated by an atomic force microscopy before and after the diffraction grating recording in order to confirm the formation of surface relief gratings. To the best of our knowledge, for the first time the photoinduced anisotropy in polyimides functionalized with azopyridine units has been compared with their supramolecular systems analoges.

Synthesis and Characterization of Aromatic Polyimides containing Trifluoromethyl Group from Bis(4-amino-2-trifluoromethylphenyl)ether and Aromatic Tetracarboxylic Dianhydrides

Aromatic polyimides, which had trifluoromethyl group at 2,2′-position of the diphenyl ether, were synthesized from bis(4-amino-2-trifluoromethylphenyl)ether (1) and previously prepared tetracarboxylic dianhydrides, 3,3′′′,4,4 ′′′- p-quaterphenyltetracarboxylic dianhydride (2d), 3,3′′′ ′,4,4′′′ ′- p-quinquephenyltetracarboxylic dianhydride (2e) and 3,3′ ′ ′ ′ ′ ,4,4 ′ ′ ′ ′ ′ - p-sexiphenyltetracarboxylic dianhydride (2f), and the properties were compared than those of corresponding polyimides from commercially available tetracarboxylic dianhydrides. The polyimides were synthesized by the conventional two-step procedure of ring-opening polyaddition in N-methyl-2-pyrrolidinone (NMP) and subsequent thermal cyclic dehydration. The polyimides were characterized by differential scanning calorimetry (DSC), thermogravimetry, and dynamic mechanical analysis (DMA). The polyimides showed excellent thermal stability, and had glass transition temperature ( Tg) at 234—300 °C. The properties of polyimides were compared with those of previously prepared polyimides, which had phenyl group at 2,2′-position of the diphenyl ether, and the effect of the trifluoromethyl groups at the 2, 2′- positions of the diphenyl ether were observed in the thermal properties, solubility and optical properties of polyimides.

Preparation and characterization of aromatic polyimides and related copolymers

AbstractCopolyimides containing BTDA‐3DDS and BTDA‐4ODA units have been synthesized by solution imidization methods. The copolyimides have high Tg's (267–283°C) and high decomposition temperatures (540–575°C; nitrogen); both properties are dependent on composition. Those copolymides with low concentrations of BTDA‐4ODA are generally soluble in organic solvents, whereas those copolyimides with higher BTDA‐4ODA content are only partially soluble or insoluble. However, all the copolyimides prepared can be compression molded. It has also been found that segmental motion above Tg is heavily suppressed in the BTDA‐4ODA homopolymer relative to that in the BTDA‐3DDS homopolymer. This reduction in molecular motion may severely hinder the solubility and fusibility of the BTDA‐4ODA homopolymer. © 1993 John Wiley & Sons, Inc.