Anisotropic photoconductivity of aromatic and semi-aliphatic polyimide films: Effects of charge transfer, molecular orientation, and polymer chain packing

Alicyclic polyimides with large band gaps exhibit superior high-temperature capacitive energy storage

“…43 Generally, the combination of a larger electron-donating diamine and a larger electron-accepting dianhydride leads to a smaller E g and more charge transfer in both intramolecular and intermolecular chains. 44 Regarding dielectric energy storage applications, it is essential to weaken both the electron-donating ability of the diamine and the electron-accepting ability of the dianhydride to enhance the E g of the PI. The electronic structures of several commercially available diamines, dianhydrides, and their corresponding PI model compounds were studied using the density functional theory (DFT) method (Fig.…”

“…Compared to their aromatic counterparts, alicyclic diamines and dianhydrides possess larger ionized potential (I P ) and smaller electron affinity (E A ) values, respectively, which can be ascribed to the absence of conjugated electrons in the alicyclic structure. 44 For instance, the I P values of aromatic diamines like ODA, MDA, PDA, and DMDB are found to be in the range 6.78 eV to 7.07 eV, while those of the alicyclic ones like CHDA and DCHM are 8.25 eV and 8.53 eV, respectively; the E A decreases from 2.62 eV for the aromatic PMDA to 0.54 eV and 0.18 eV for alicyclic CBDA and HPMDA, respectively. Additionally, it is noted that introducing fluorine groups in the benzene rings linked to the terminal amino group can also effectively increase the I P of diamines, e.g., TFMB having an I P of 7.54 eV.…”

Synthesis and properties of modified thermoplastic polyimide films with good dielectric properties at high frequency and enhanced thermal stability via incorporation of rigid ester and biphenyl structural units

“…35,36 A lower ε LUMO value for the dianhydride and a higher ε HOMO value for the diamine could roughly indicate higher reactivity of the monomers. 37 In the current work, the ε LUMO and ε HOMO values of the monomers were calculated according to the density functional theory (DFT)/B3LYP methods with Gaussian 09 software using the 6-311G(d, p) basis set 38 2).…”

Compression and Thermal Expansion Behaviors of Highly Crystalline Polyimide Particles Prepared from Poly(amic acid) and Monomer Salts

“…Fully aromatic polyimides (PIs) are high-performance engineering polymers that have been used in aerospace, electric, electronic, and optical applications owing to their excellent mechanical strength, thermal and chemical stabilities, radiation resistance, and flexibility. , PIs are typically used as films exhibiting various physical properties, such as optical, thermal, and electronic properties, which are significantly influenced not only by the primary structure but also by the stereochemical structures, that is, the conformation and orientation of PI chains and their aggregation structures. − In this study, we observed that the refractive indices of semicrystalline PI films increase with an increase in the degree of chain packing . In addition, we reported that the photoconductivity of PI thin films can be effectively enhanced by suppressing the charge recombination, which is accomplished by reducing chain packing . Therefore, detailed examinations of the aggregation structures in the solid state are essential for understanding the physical properties of PI films.…”

“…7 In addition, we reported that the photoconductivity of PI thin films can be effectively enhanced by suppressing the charge recombination, which is accom-plished by reducing chain packing. 8 Therefore, detailed examinations of the aggregation structures in the solid state are essential for understanding the physical properties of PI films.…”