Enhancement of Dimensional Stability in Soluble Fluorinated Polyimides via the in Situ Formation of Lanthanum(III)−Oxo−Polyimide Nanocomposites

The synthesis and characterization of composite inorganic−polyimide films is described by adding diaquotris(2,4-pentanedionato)lanthanum(III) to soluble, low dielectric, colorless polyimides formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride/1,3-bis(3-aminophenoxy)benzene (6FDA/APB), and 6FDA/2,2-bis[4-(4-aminophenoxy]hexafluoropropane (6FDA/BDAF). The [La(acac) 3 (2H 2 O) 2 ]-containing polyimide films were thermally treated from 220 to 340 °C which resulted in substantial lowering of the linear coefficients of thermal expansion at low metal concentrations (<4%) without sacrificing other essential thermal and mechanical properties of the parent polyimide. TEM data are consistent with particle sizes for the lanthanum ion-containing species which are in the nanometer range; thus, the visual clarity of the films was maintained. Refractive index measurements indicate that the films are isotropic. Addition of the lanthanum complex to the poly(amic acid) form of 6FDA/APB and 6FDA/BDAF followed by thermal curing to 300 °C yields low molecular weight crazed polyimide films.