Synthesis of novel biphenyl-fused alicyclic tetracarboxylic dianhydride and its performance in thermostable and transparent colorless polyimides

Biphenyl fused alicyclic tetracarboxylic dianhydride, 6,6′,7,7′-tetracarboxylic dianhydride-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-binaphthalene (OHBNDA) was successfully synthesized from biphenyltetracarboxylic dianhydride (BPDA) through hydrolysis, reduction, bromination, and Diels–Alder reaction. Three OHBNDA-based polyimides (PIs) were synthesized by one-step polycondensation at high temperature with 9,9-bis(4-aminophenyl)fluorene (BAFL), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB), and 4,4′-diamino-2,2′-dimethyl-1,1′-biphenyl ( m -TolDA) diamines, respectively. These PIs have moderate molecular weights and good solubility in polar organic solvents, such as N , N -dimethylformamide, dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). OHBNDA-TFMB, OHBNDA- m -TolDA, and OHBNDA-BAFL display glass transition temperatures ( T g s) of 309, 329, and 377°C from differential scanning calorimetry (DSC) curves, and the decomposition temperatures at 5% weight loss ( T d5 ) of as high as 522, 507, and 548°C under nitrogen, respectively. Meanwhile, these PI films also show good optical transparency with the cut-off wavelength <315 nm and the transmittance >75% at 400 nm. These results confirm that aryl-fused alicyclic tetracarboxylic dianhydrides can afford transparent/colorless PIs with high thermal stability, especially the higher decomposition temperatures than the wholly alicyclic dianhydrides.