Synthesis and properties of polyimides derived from Cis- and Trans-1,2,3,4-cyclohexanetetracarboxylic dianhydrides

摘要: Abstract Cis -1,2,3,4-cyclohexanetetracarboxylic dianhydride ( cis -1,2,3,4-CHDA) was synthesized. It found that under such conditions as heating or boiling in acetic anhydride, -1,2,3,4-CHDA could be converted to its trans -isomer. The process of thermal isomerization monitored by 1 H NMR spectra and the mechanism conversion proposed. Their absolute structures - -1,2,3,4-CHDAs were elucidated single crystal X-ray diffraction. polycondensations with aromatic diamines 4,4′-oxydianiline (ODA), 4,4′-methylenedianiline (MDA), 4,4′-diamino-3,3′-dimethyldiphenylmethane (DMMDA), 4,4′-bis(4-aminophenoxy)benzene (TPEQ), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) studied. is easy obtain higher molecular weight polyimides from using conventional one-step two-step methods. However, derived not prepared usual methods (solid content ca. 10%) owing trend forming cyclic oligomers. Increasing concentration monomers give -polymers. All -polyimides soluble at room temperature aprotic polar solvents phenolic some them even chloroform tetrahydrofuran, while corresponding -polymers showed poor solubility compared good stability 5% loss temperatures air over 415 °C. Furthermore, have glass transition T g s) than -polyimides. flexible polyimide films possessed a tensile modulus range 2.1–3.6 GPa, strength 42–116 MPa, an elongation break 4–18%. These exhibited cutoffs wavelengths around 270 nm entirely colorless. amorphous pattern according Wide angle diffraction measurements. differences polymerization properties explained structural changes resulted isomerism.