The Improvement of Surface Energy of BPDA-EDA Polyimide by Controlling Molecular-Level Structure

The surface properties (water sorption and repellency, adhesion) are closely related to the surface tension of polymer solid. Critical surface tension γ C and surface tension γ S of a polymer solid have been estimated by the contact angle method by our quantitative imaging system. BPDA (3,3′,4,4′-biphenyl tetracarboxylic dianhydride) – EDA (4,4′-ethylenedianiline) polyimide was successfully synthesized. The critical surface tensions γ C were analyzed by a Zisman plot, a Young-Dupré-Good-Girifalco plot, and a log (1 + cos θ) vs log γ L plot. The surface tension γS of BPDA-EDA polyimide was evaluated using the geometric mean equation and our multiple regression analysis. The calculated values of (a dispersion component), (a polar component), (a hydrogen bonding component), and are 30.49, 4.52, 0.08, and 35.09 mN·m−1, respectively. The γ S of BPDA-EDA polyimide containing two methylene groups is smaller than those of the polyimides containing both methylene group and ether group.