Low dielectric constant and organosolubility of polyimides derived from unsymmetric phthalic-thioether-naphthalic dianhydrides

A series of polyimides (PIs) with low dielectric constant were synthesized via a polycondensation from two new unsymmetric phthalic-thioether-naphthalic dianhydride isomers which were synthesized from 3- or 4-chlorophthalic anhydride by a four-step procedure. The introduction of the unsymmetric phthalic-thioether-naphthalic dianhydride into polymer backbone is regarded as an effective way to increase the free volume and decrease the intermolecular force and packing ability of the resulting polymers. Thus, the novel PIs exhibit low dielectric constant, low moisture absorption good solubility, high modulus, and high glass transition temperature. The polyimides show good solubility in phenol, dipolar aprotic solvents, and other common organic solvents. In addition, the isomeric effect of 3- and 4-thioether-linked phthalic anhydride on the properties of PIs was discussed.