Solvent induced phase separation in a nylon 6-b-polyimide-b-nylon 6 triblock copolymer

A series of new nylon 6-b-polyimide-b-nylon 6 (triblock) copolymers have been synthesized via condensation polymerization of the polyimide component and anionic polymerization of the nylon 6 component. The polyimide component is prepared from bisphenol-A dianhydride (BisA-DA) and bisaniline-P diamine (BisP) with end-capped functional groups. After the polyimides are dissolved in caprolactam, the nylon 6 anionic polymerization is initiated by the functional groups of the polyimides. The triblock copolymers can be dissolved in both m-cresol and 1,6-hexanediol. Of the two components present in the copolymers, nylon 6 crystallizes partially and BisA-DA/BisP is amorphous. Based on differential scanning calorimetry, dynamic mechanical analysis, wide angle X-ray diffraction, small angle X-ray scattering and transmission electron microscopy experiments, the copolymer films prepared from the 1,6-hexanediol solution are phase separated. The BisA-DA/Bis P and the nylon 6 components show little miscibility in the interlamellar amorphous region. However, in the films prepared from the m-cresol solution both components are largely miscible in the inter-lamellar amorphous region. This is due to the different solvation power of the two solvents with respect to the polyimide and nylon 6.