Synthesis and Characterization of Polyimides Derived From Cyano-Containing 1,4-Bis(4-aminophenoxy)benzene Monomers

A series of three new cyano-containing diamines based upon 1,4-bis(4-aminophenoxy)benzene was synthesized and polymerized with six different dianhydrides to yield 18 different polyimides. Due to the high dipole moment of the cyano group, it was believed that these polymers would display differing degrees of electroactivity depending upon the degree and position of cyano substitution. The type of dianhydride bridging group and length are also factors that affect the electroactivity of polyimides. Polyimides based upon 1,4-bis(4-aminophenoxy)benzene were used as reference materials by which the respective cyano-containing analogs were compared. As the degree of cyano group substitution increased, the glass transition temperature increased. As cyano substitution increased, the polymer chain flexibility decreased due to hindered rotation about the phenyl-ether-phenyl linkages in the diamine portion of the polymer. The tensile moduli ranged from 2.97 to 4.57 GPa and ultimate tensile strengths from 79 to 156 MPa, which are typical values of aromatic polyimides.