Polyimides possessing bulky phosphorus groups: Synthesis and characterization

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.