A series of polyimides with bulky pendent groups containing phosphorus were obtained from polymerization of various dianhydrides with a new diamine (2DOPO-A) bearing two bulky (9,10-dihydro-9-oxa-10-oxide-10-phosphaphenanthrene-10-yl) (DOPO) substituents. The resulting polymers had inherent viscosities of 0.15-0.32 dL/g and glass transition temperatures of 260-283°C. The polyimides were soluble in some organic solvents due to the incorporation of bulky and polar DOPO groups. The non-coplanar cardo structure of 2DOPO-A also contributed to the improvement in the solubility of the polyimides. Incorporating DOPO groups into polyimides resulted in polymers with low initial decomposition temperatures (IDT; 310-362°C) due to the independent decomposition of the DOPO groups. Thermogravimetric analysis showed that the DOPO-containing polyimides exhibited high integral procedural decomposed temperatures (IPDT) of 891-950°C. Incorporation of DOPO group into polyimides also improved their weight loss rate, thermal stability, thermal-oxidative stability, and heat insulating property in the high temperature region. ; JNL0002917