Organosoluble semi-alicyclic polyimides derived from 3,4-dicarboxy-1,2,3,4-tetrahydro-6-tert-butyl-1-naphthalene succinic dianhydride and aromatic diamines: Synthesis, characterization and thermal degradation investigation

Abstract

Semi-alicyclic polyimides (PI-1–PI-4) have been prepared from a newly-developed alicyclic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-6-tert-butyl-1-naphthalene succinic dianhydride (TTDA) and various aromatic diamines. The asymmetrical alicyclic tetralin structure in TTDA endowed the derived PI resins good solubility in various organic solvents. They were soluble not only in polar aprotic solvents but also in solvents with low boiling points including dichloromethane and tetrahydrofuran. Flexible and tough PI films were successfully cast from their N-methyl-2-pyrrolidone (NMP) solution except PI-1 derived from TTDA and 4,4′-oxydianiline (ODA). The PI films exhibited good optical transparency in the ultraviolet and visible light region with optical transmittances around 80% at a wavelength of 400nm. The PI films showed good thermal stability up to 400°C in nitrogen, after that they thermally decomposed rapidly. The thermal degradation behaviors of the PIs were investigated by means of thermogravimetric analysis-mass spectrometry (TG-MS), thermogravimetric analysis-Fourier transform infrared spectrometry (TG-FTIR) and the real time FTIR spectra (RT-FTIR) analysis techniques. The results revealed that the decomposition of PI-1 (as a representative) took place mainly in the range of 450–550°C. The major degradative fragments at 500°C were clearly identified as the tert-butyl-substituted tetralin moiety and its dealkylation products. Therefore, it can be deduced that for the TTDA-PIs, the single bond bridge attached the maleic anhydride and tetralin anhydride units in TTDA moiety might break first during the heating; thus producing the tetralin fragments.