Density Functional Theory-Based Approach For Dielectric Constant Estimation of Soluble Polyimide Insulators

Evaluation of the insulating properties of polymers, such as the dielectric constant and dissipation factor, is crucial in electronic devices, including field-effect transistors and wireless communication applications. This study applies density functional theory (DFT) to predict the dielectric constant of soluble polyimides (SPIs). Various SPIs containing trifluoromethyl groups in the backbone with different pendant types, numbers, and symmetries are successfully synthesized, and their dielectric constants are evaluated and compared with the DFT-estimated values. Two types of DFT-optimized SPIs, single-chain and stacked-chain models, are used to describe the local geometries of the SPIs. In addition, to reveal the relationship between the molecular structure and dielectric constant, further investigations are conducted by considering the dielectric constant of composing ionic and electronic components. The DFT-estimated static dielectric constant of the single-chain model accurately reproduces the corresponding experimental value with at least 80% accuracy. Our approach provides a rational and accelerated strategy to evaluate polymer insulators for electronic devices based on cost-effective DFT calculations.

Super-heat resistant, transparent and low dielectric polyimides based on spirocyclic bisbenzoxazole diamines with Tg > 450°C

Maintaining ultra-high heat resistance and sufficient colorless transparency at the same time is a challenge for polymer materials because of conflicting design principles, but such materials are urgently needed for...

High-performance non-volatile resistive switching memory based on a polyimide/graphene oxide nanocomposite

Chemical structure of PI-GO, schematic structure of the ITO/PI-GO/Al device and its memory characteristics.

Soluble Polyimides Bearing (cis, trans)-Hydrogenated Bisphenol A and (trans, trans)-Hydrogenated Bisphenol A Moieties: Synthesis, Properties and the Conformational Effect

In this work, hydrogenated bisphenol A (HBPA) based dinitro mixed isomers (1a′ and 1a) were synthesized and separated via vacuum distillation under the monitor of DSC and ¹H NMR. Corresponding diamines (2a′ and 2a) were separately polycondensed with five commercial dianhydrides via a two-step thermal imidization to obtain PI-(1′-5′) and PI-(1-5). All the polyimides could afford flexible, tough, and transparent films, and most of them were readily soluble not only in common polar solvents like DMAc, but also in low boiling point solvents such as chloroform. ¹H NMR spectra of the polyimides demonstrated that HBPA moiety showed no conformation changes during the preparation of polymers. For a given dianhydride, PI-(1-5) exhibited better thermal stability than that of PI-(1′-5′), this can be attributed that the equatorial, equatorial C–O in PI-(1-5) promoted denser and more regular molecular chain stacking, as can be evidenced by the WAXD and geometric optimization results. Additionally, when the dianhydride was ODPA, BPADA or 6FDA, no apparent difference was found in either the transmittance or solubility between two series of polyimides, which could be attributed that twisted and flexible ether linkages, as well as bulky substituents, led to the “already weakened” inter- and intramolecular CT interaction and cohesive force. However, when it came to rigid and stiff dianhydride, e.g., BPDA, PI-3′ took an obvious advantage over PI-3 in transmittance and solubility, which was possibly owed to the larger molecular chain d-spacing imparted by equatorial, axial C–O. An overall investigation of PI-(1′-5′) and PI-(1-5) on aspects of thermal, mechanical, morphological, soluble and optical performance values was carried out, and the conformation effects of HBPA isomers on the properties of two series of polyimides were discussed in detail.

Preparation of Polyimide/Graphene Oxide Nanocomposite and Its Application to Nonvolatile Resistive Memory Device

2,6-Diaminoanthracene (AnDA)-functionalized graphene oxide (GO) (AnDA-GO) was prepared and used to synthesize a graphene oxide-based polyimide (PI-GO) by the in-situ polymerization method. A PI-GO nanocomposite thin film was prepared and characterized by infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and UV-visible spectroscopy. The PI-GO film was used as a memory layer in the fabrication of a resistive random access memory (RRAM) device with aluminum (Al) top and indium tin oxide (ITO) bottom electrodes. The device showed write-once-read-many-times (WORM) characteristics with a high ON/OFF current ratio (Ion/Ioff = 3.41 × 10⁸). This excellent current ratio was attributed to the high charge trapping ability of GO. In addition, the device had good endurance until the 100th cycle. These results suggest that PI-GO is an attractive candidate for applications in next generation nonvolatile memory.

Synthesis and properties of soluble aromatic polyimides from novel 4,5-diazafluorene-containing dianhydride

A dianhydride monomer containing 4,5-diazofluorene was synthesized, and the corresponding organo-soluble polyimides exhibited good comprehensive properties.

Design and synthesis of high heat-resistant, soluble, and hydrophobic fluorinated polyimides containing pyridine and trifluoromethylthiophenyl units

In this study, a novel diamine monomer, 4-(4-trifluoromethylthiophenyl)-2,6-bis(4-aminophenyl)pyridine (FTPAP) was synthesized through two-step reaction from 4-trifluoromethylthiobenzaldehyde and 4-nitroacetophenone as raw materials, and then the structure of FTPAP was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance, and mass spectrometry. A series of fluorinated polyimides were prepared from FTPAP with five commercial dianhydrides, namely, pyromellitic dianhydride, biphenyl tetracarboxylic dianhydride, oxydiphtahalic anhydride, benzophenone tetracarboxylic dianhydride, and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride. The structure and performance of the fluorinated polymers were fully characterized by FTIR, differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray diffraction (WAXD). The inherent viscosity of polymers ranged from 0.41 to 1.45 dL g−1. These polymers displayed good solubility in polar aprotic solvents, such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone, at room temperature or on heating. Furthermore, they exhibited outstanding thermal stability with glass transition temperatures beyond 305°C, and the temperature of 10% weight loss was in the range of 514–573°C with more than 56% residue at 800°C under nitrogen. Moreover, they showed high optical transparency with the cutoff wavelengths in the range of 385–457 nm and excellent hydrophobic property with contact angle in the range of 82.8–97.6°. In addition, the results of WAXD indicated that all of the polymers presented amorphous structure.

Low Dielectric Polyetherimides Derived from Bis[4-(4-(4-aminophenoxy)-2-tert-butylphenoxy)phenyl] Sulfone and 4,4'-Bis[4-(4-aminophenoxy)-2-tert-butylphenoxy]perfluorobiphenyl

Two diamines, bis[4-(4-(4-aminophenoxy)-2-tert-butylphenoxy)phenyl] sulfone (PSNH₂) and 4,4'-bis[4-(4-aminophenoxy)-2-tert-butylphenoxy)perfluorobiphenyl (PFNH₂), were prepared from 3-tert-butyl-4-hydroxyanisole using a four-step procedure, including two nucleophilic substitutions, demethylation, and catalytic reduction. On the basis of PSNH₂ and PFNH₂, two series of low dielectric polyetherimides (PEIs) were prepared. Both series of PEIs exhibit moderate-to-high thermal properties, including a glass transition temperature (T _g) > 259 °C (depending on the rigidity of dianhydride), a 5 wt % decomposition temperature (T _d5%) > 496 °C, and a coefficient of thermal expansion < 66 ppm/°C. Because of the hydrophobic tert-butyl phenylene oxide structure, both series of PEIs show excellent dielectric properties, with a dielectric constant as low as 2.4-2.7. The structure-property relationship of both series of PEIs is discussed in this work.

Instantaneous Pulsed-Light Cross-Linking of a Polymer Gate Dielectric for Flexible Organic Thin-Film Transistors

We report the instantaneous pulsed-light cross-linking of polymer gate dielectrics on a flexible substrate by using intensely pulsed white light (IPWL) irradiation. Irradiation with IPWL for only 1.8 s of a poly(4-vinylphenol) (PVP) thin film with the cross-linking agent poly(melamine-co-formaldehyde) (PMF) deposited on a plastic substrate was found to yield fully cross-linked PVP films. It was confirmed that the IPWL-cross-linked PVP films have smooth pinhole-free surfaces and exhibit a low leakage current density, organic solvent resistance, and good compatibility with organic semiconductor, and that they can be used as replacements for typical PVP dielectrics that are cross-linked with time and energy intensive thermal heating processes. The synchronization of the IPWL irradiation with substrate transfer was found to enable the preparation of cross-linked PVP films on large area substrates with a highly uniform capacitance. Flexible OTFT based on IPWL-cross-linked PVP dielectrics were found to exhibit good electrical performance that is comparable to that of devices with thermally cross-linked PVP dielectric, as well as excellent deformation stability even at a bending radius of 3 mm.

A strategy for preparing spirobichroman dianhydride from bisphenol A and its resulting polyimide with low dielectric characteristic

The high performance polyimide, SBC-DDM, exhibits a large free volume, leading to outstanding organo-solubility and a low dielectric constant.

Synthesis and characterization of organosoluble, transparent, and hydrophobic fluorinated polyimides derived from 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene

A novel aromatic fluorinated diamine monomer, 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene, was synthesized by coupling of 2-isopropylaniline and 4-(trifluoromethyl)benzaldehyde and its structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, and mass spectrometry, and then used to prepare a series of fluorinated polyimides (FPIs) by polycondensation reaction with various commercial dianhydrides via conventional one-step method. The obtained FPIs present excellent solubility in most organic solvents and enough to cast into tough and flexible films. All the FPI films show good optical transparency and light color with the cutoff wavelengths in range of 307–362 nm and the average transmittance above 86%. These polymer films also exhibit high glass transition temperature in range of 261–331°C and thermal stability with 10% weigh loss above 463°C under nitrogen atmosphere. Furthermore, they exhibit outstanding mechanical properties with tensile strengths of 65.9–94.3 MPa, elongation at break of 11.4–13.8%, Young’s modulus of 1.6–1.9 GPa, and low dielectric constants in range of 2.75–3.10 at 1 MHz as well as prominent hydrophobicity with the contact angle in the range of 87.3–93.9°.

Synthesis and characterization of optically active polyimides and their octa(aminophenyl)silsesquioxane nanocomposites

New optically active diamine (3,5-diaminophenyl)((R)-3,4-dihydro-1-phenylisoquinoline-2(1H)-yl)methanone was successfully prepared. Optically active polyimides (PIs) were synthesized by reacting the prepared diamine with the aromatic tetracarboxylic dianhydrides, namely, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride/pyromelltic dianhydride by thermal imidization method and characterized using Fourier transform infrared and nuclear magnetic resonance spectral techniques. Additionally, PI nanocomposites were also prepared by incorporating amino-functionalized polyhedral oligomeric silsesquioxane named as octa(aminophenyl)silsesquioxane (OAPS). The cut-off wavelengths of PIs and their nanocomposites were found to be less than 350 nm, indicating that the PIs are transparent. The PIs and their nanocomposites were found to have glass transition temperature between 204°C and 269°C (differential scanning calorimetric analysis). The 10% weight loss temperature and char yield were found to be 319.5–420.3°C and 26.3–62.7%, respectively. The PIs were found to be amorphous as indicated by X-ray analysis. The scanning electron microscopic images of the nanocomposites also reveal uniform distribution of the nanoparticles in the nanocomposite. PIs and PI/OAPS nanocomposites were found to have low dielectric constant in the range of 2.59–3.36.

Synthesis of novel biobased polyimides derived from isomannide with good optical transparency, solubility and thermal stability

Novel biobased polyimides with good optical transparency and combined properties were synthesized from biomass isomannide-derived diamines and/or dianhydrides, thus providing a new approach to develop sustainable materials of high performance.

Design and preparation of novel fluorescent polyimides containing ortho-linked units and pyridine moieties

A novel pyridine-containing aromatic diamine monomer, 4-[4-hydroxyphenyl]-2,6-bis[4-(2-aminophenoxy)phenyl]pyridine (p,o-HAPP), was synthesized by a modified Chichibabin reaction of p-Hydroxybenzaldehyde and a substituted acetophenone, 4-(2-nitrophenoxy)acetophenone (p,o-NPAP), followed by a reduction of the resulting dinitro compound 4-[4-hydroxyphenyl]-2,6-bis[4-(2-nitrophenoxy)phenyl]pyridine with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to prepare a series of pyridine-containing polyimides (PIs) by polycondensation with various aromatic dianhydrides in N,N-dimethylformamide (DMF) via the conventional two-step method. The inherent viscosities of the resulting poly(amic acids) and PIs were in range of 0.62-0.76 and 0.52-0.64 dL/g, respectively. The obtained novel PIs exhibited high solubility in common organic solvents, such as m-Cresol, DMF, N,N-dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone (NMP), tetrahydrofuran, and chloroform. Meanwhile, flexible PI films were obtained, which had excellent thermal stability, with the glass transition temperature (T g) of 259.8-323.4 °C and the temperature at 10% weight loss of 485.5-576.4 °C in nitrogen atmosphere. The protonated polymer showed UV-vis absorption in the region 200-400 nm and displayed strong fluorescence intensity (470 nm) in NMP solution.

Novel polypyrrolones containing fluorenyl groups in the main chain: Synthesis and characterization

A novel aromatic tetraamine, 2′,7′-bis(3,4-diaminophenoxy)-spiro(fluorene-9,9′- xanthene), was synthesized, which was employed to react with various commercial available aromatic dianhydrides to yield a series of polypyrrolones (PPys). The intermediate poly(amide amino acid) had inherent viscosities of 0.28–0.35 g/dl and could be thermally converted into lightly yellow PPys films. All the resulting PPys exhibited good thermal stabilities. The glass-transition temperatures were in the range of 371–386°C, and the temperatures of 5 and 10% weight loss were 472–549°C and 552–612°C in nitrogen, respectively; the residual weight was above 62% at 800°C. In addition, the PPys films had tensile strengths in the range of 42.3–85.8 MPa, tensile moduli of 1.8–2.5 GPa, and elongations at break of 6.8–7.4%. The polymer films also exhibited excellent alkaline hydrolysis resistance, retaining their original shapes and toughness after boiling for 7 days in 10% sodium hydroxide solution.