Semi-aromatic thermosetting polyimide resins containing alicyclic units for achieving low melt viscosity and low dielectric constant

Semi-aromatic thermosetting polyimide resins containing alicyclic units were prepared by the polymerization of 1,2,4,5- cyclohexanetetrcarboxylic dianhydride (HPMDA), aromatic diamines and nadic anhydride (NA) served as reactive capping agent. To obtain the homogeneous poly (amic ester) (PAE) matrix resins, the 2-methoxyethanol (EGME) was used to esterify HPMDA. The chemical structure of PAE resins dried at different temperatures were characterized in detail by FT-IR, 1H NMR and TGA-GCMS. Compared with the full-aromatic API-1, the alicyclic units with less Pi(π) bonds and twisted structure endow the semi-aromatic PI resins with loose polymer chains packing and weak intermolecular forces, which contribute to low melt viscosities, good solubility and excellent dielectric properties. The cured semi-aromatic PI resins show low dielectric constants ranging from 2.8 to 3.0 and dielectric loss of <0.01 at a range of frequencies from 1GHz to 12GHz. The results indicate the semi-aromatic thermosetting PI resins are promising dielectric interlayer materials for high frequency substrates.