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

Abstract

AbstractBiphenyl 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 (Tgs) of 309, 329, and 377°C from differential scanning calorimetry (DSC) curves, and the decomposition temperatures at 5% weight loss (Td5) 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.