Semiaromatic Polyimides based on Bis(Aminomethyl)Bicyclo[2.2.1]Heptane

Abstract

Semiaromatic polyimides with a polyalicyclic structure were prepared by the polycondensation of bis(aminomethyl)bicyclo[2.2.1]heptane (BBH) with aromatic dianhydrides. The corresponding poly(amic acid)s possessed an inherent viscosity range of 0.60-1.00 dl g −1 . The polyimides were soluble in organic polar solvents and most of them formed flexible, free-standing films. The polyimides had good thermal stability with no significant weight loss up to approximately 400 • C and possessed a 5% weight loss temperature range of 428-465 • C. These polyimide films showed a tensile modulus range of 1.4-3.0 GPa, a tensile strength range of 62-115 MPa, and an elongation at break range of 5.4-6.1%. The semiaromatic polyimide films exhibit a cut-off wavelength around 322-362 nm and are entirely colourless, while the cut-off wavelengths of PI(PMDA-DDE) and PI(BPDA-DDE) films were 426 and 376 nm respectively. The origin of coloration in the aromatic polyimides and the lack of colour in the semiaromatic polyimides were elucidated from the standpoint of molecular orbital (MO) calculations of the model compounds using semiempirical AM1 and INDO/S methods. The calculated λ max of the M(PMDA-BBH) was 371 nm, and the first excited state is mainly characterized by an n-π * transition. Based on both the MOs and the difference in electron density between the ground and the first excited states, the first excited state is attributable to light-induced polarization in the five-membered imide ring. The λ max of the M(PMDA-DDE) model for a representative aromatic polyimide was calculated to be 392 nm. From the charge difference map, it is theoretically evident that the coloration in the aromatic polyimides caused intramolecular charge transfer between the diamine and dianhydride moieties.

Copolyimides containing alicyclic and fluorinated groups: Characterization of the film microstructure

“…By solution polymerization, the syntheses of polyimides based on such monomers can be more or less difficult than for aromatic polyimides. For instance, polyimides based on alicyclic diamine are more difficult to obtain because of the high basicity of such diamines 1–3. However, nonaromatic dianhydrides such as bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride (BCDA) and bicyclo[2.2.2]‐octane‐2,3,5,6‐tetracarboxylic dianhydride were reported to display higher reactivity with aromatic diamines than pyromellitic dianhydride (PMDA) 4.…”

C3-Chiral Tripodal Amido Complexes

“…By minimizing or eliminating CTC formation, low color or virtually colorless polyimide films with improved transparency can be obtained 6, 7. Colorless soluble polyimides can be obtained by using aliphatic dianhydride or diamine monomers8–11; however, the long term thermal stability is somewhat decreased because of the incorporation of less stable aliphatic segments.…”

Ultrafast Spectroscopic Analysis of Pressure-Induced Variations of Excited-State Energy and Intramolecular Proton Transfer in Semi-Aliphatic Polyimide Films

“…The precursors of the semi-aliphatic polyimides (Al-PIs), poly­(amic acid)­silylester (PASE), were prepared using an in situ silylation method. − The three types of alicyclic diamines were dissolved in DMAc with a 1.05 molar equiv of BSTFA and stirred for approximately 0.5 h. An equimolar amount of dianhydride was then added to the diamine. The PASE solutions were then stirred at room temperature for 48 h. Trimethylsilylation of the amino groups by BSTFA can avoid a salt formation between the unreacted amino groups and the generated carboxyl groups from a ring opening reaction of the dianhydride moieties. − …”