Masahiro Yoshioka

Preparation and Properties of Polyisoimides as a Highly Dimensionally Stable Polyimide Precursor with Low Dielectric Constant

Fluorinated polyimides (PIs) with low dielectric constant and high dimensional stability have been developed using polyisoimides (PIIs) as a polyimide precursor. The PIIs were prepared by the ring-opening polyaddition of the dianhydrides pyromellitic dianhydride, biphenyltetracarboxylic dianhydride and 4, 4′-hexafluoropropylidenedi(phthalic anhydride) with the diamines 2, 2′-dimethylbenzidine and 2, 2′-bis(trifluoromethyl)benzidine, followed by treatment with trifluoroacetic anhydride/triethylamine or dicyclohexylcarbodiimide in N;N-dimethylacetamide. The PIIs were soluble in a wide range of solvents including dipolar aprotic solvents, cyclohexanone and tetrahydrofuran at room temperature, and easy to convert to corresponding PIs by high thermal treatment. The resulting PIs showed low dielectric constants of less than 3 at 1 MHz as well as low CTEs. Furthermore, during the isomerization reaction, migration of copper in the PI film was hardly observed.

One-Pot Synthesis of Aromatic Polycarbodiimide by in Situ Activation of Diamine:

A one-pot synthesis of aromatic polycarbodiimide from aromatic diamine has been developed. This method involves the preparation of carbamate by the reaction of 4, 4′-hexafluoroisopropylidenebis(p-phenyleneoxy)dianiline (6FPA) with phenylchloroformate, followed by the transformation of the carbamate with trimethylsilylchloride-triethylamine to diisocyanate, and then the polycondensation of the resulting diisocyanate in the presence of 3-methyl-1-phenyl-2-phosopholene-1-oxide. The polycarbodiimide (6FPCD) from 6FPA was obtained in quantitative yield having a number average molecular weight up to 5000. The thermal treatment of 6FPCD gave a crosslinkined polymer having a high glass transition temperature up to 200 °C.