Papers by Keyword: Polyimide

Abstract: Our laboratory explores organic polymer materials, focusing on utilizing polyimide (PI) films [1] as the resistive switching layer in resistive random-access memory (ReRAM). This study investigates how UV-induced molecular changes in PI films lead to resistance transitions resembling electrical switching. Based on this characteristic, a novel resistive optoelectronic memory device has been developed and explores methods for tuning their energy gap (Eg) through process modifications. By analyzing the physical and electrical properties of the films, we evaluate their UV absorption efficiency and molecular structural transformations. The study identifies the optimal UV wavelength for operation and measures device programming efficiency and data retention. Finally, through process control to modulate the energy gap of PI films.

Abstract: Laser-induced graphene (LIG) has gained much attention as a promising material for advanced energy storage solutions, including supercapacitors, due to its many advantages. This study presents the fabrication and characterization of LIG electrodes for electrochemical energy storage, a significant contribution to the field. Laser writing parameters such as laser power and scanning speed were optimized to produce highly conductive and electrochemically active LIG material. Transmission electron microscopy and Raman spectroscopy confirmed the formation of high-quality graphene with excellent electrical conductivity. A systematic investigation of the electrochemical performance of the LIG electrodes was conducted using various aqueous electrolytes, including H₂SO₄ (sulfuric acid), KOH (potassium hydroxide), NaOH (sodium hydroxide), and Na₂SO₄(sodium sulfate), all at the same concentration. A solid-state supercapacitor was assembled using two separate LIG electrodes, and its electrochemical performance was analyzed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The specific areal capacitance of the supercapacitor was determined to be 6.9 mF/cm² at a scan rate of 10 mV/s. The device demonstrated performance consistent with many previously reported LIG-based supercapacitors.

Abstract: Some membrane processes, such as organic solvent nanofiltration, require membranes with strong chemical resistance to endure harsh chemical environments. Polymeric membranes, while possessing excellent separation properties, are mostly lacking in this area. Due to its inherent chemical resistance, polyimide (PI) stands out as a highly promising material, with the potential to excel in diverse applications where resilience to harsh environments is essential. Therefore, this study attempts to perform a surface modification on PI membrane via radiation induced graft copolymerization (RIGC) of methyl methacrylate (MMA) as the monomer, known to further enhance chemical resistance and organic solvent separation of the membrane. The effects of MMA concentration (0.5, 1.0, 1.5 and 2.0 M) and radiation dose (50, 100, 150 and 200 kGy) on the degree of grafting of poly (methyl methacrylate) (PMMA) and the properties of resultant PI-graft (g)-PMMA membranes were investigated. The PI-g-PMMA membranes were characterized using atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis and contact angle analysis. The interplay between MMA concentration and radiation dose has not only affected the degree of grafting but also the membrane properties. In conclusion, the findings feature the immense potential of the RIGC technique to modify a highly stable PI membrane to survive in demanding applications within harsh chemical environments.

Abstract: The current research focus in our group is on utilizing the polymer material polyimide (PI) as the resistance switching layer for resistive memory. In recent years, PI resistive photomemory (RePM) [1] has been developed, capitalizing on the photosensitive properties of PI films in the ultraviolet light band. PI initially possesses two chemical structures, Aromatic and Quinoid, the PI film undergoes transformation when exposed to ultraviolet light. By employing various processing methods to control the ratio of Quinoid and Aromatic molecular chains in the PI film, and through FTIR measurements of chemical structure changes before and after illumination, we gain insights into the variations in the molecular chain ratio due to different experimental parameters. FTIR analysis reveals that changes in spin coating speed influence the molecular ratio within the film, attributed to differences in molecular chain shapes and lengths. Experimental results demonstrate that optimizing the spin coating process enhances the operational efficiency of RePM, significantly extending data retention time.

Abstract: This study investigated the impact of different Polyamic Acid (PAA) solid content on Polyimide (PI) film precursors, adjusting the molecular chain density after dehydration and cyclization to improve the operating voltage and leakage current of resistive random access memory (RRAM). This work modulated 1.5%, 5%, and 15% PAA solutions to form PI film as a resistance switching layer. After modulating the molecular chain density in the PI film, the goal is to improve the device’s operating characteristics. According to the result, the PI film with a higher concentration can achieve a lower operating electric field and reduce the leakage current, improving operational stability and reliability.

Abstract: Co-Pоly (Urethane-Imide) s (CPUI) based on pоly (diethyleneglycol) adipate diol, tolylenediisocyanate, multinucleate dianhydrides and diamines were synthesized. The films and moldings from CPUI were processed and their mechanical characteristics were evaluated. Distinctions of specifications of the films formed from polymer solutions and the moldings formed from melt polymers are indicated when using the same starting CPUI. It appears that films and moldings possess typical properties of elastomers. The reprocessing of studied copolymers by using the injection molding method allows to assign CPUI to the thermoplastic elastomers or so-called thermoelastoplasts.

Abstract: Polyimide/Al₂O₃ films were prepared by the surface modification with different hydrolysis time, ion exchange technique and heat treatment using polyimide films as the substrates and aluminum chloride as the precursor of Al₂O₃. The morphology, thermal properties and electrical properties of the composite films were characterized and tested. The results indicated the alumina distributed in certain thickness on the surface of the films and there was a clear interface layer between the alumina layer and the substrate. The breakdown strength of the composite films maintains the excellent properties of the pristine film while the thermal and corona-resistant time properties of composite films were better than the pristine film due to introducing aluminum oxide. The composite film which used KOH to treat for 90 min has the longest corona-resistant time (101.2 min), which was almost 10 times longer than the pristine film.

Abstract: The temperature-time modules of drying and heat treatment of polyetherketones and polyphenylene sulfides are revealed; which made it completely possible to get rid of sorption water and an upper limit noticeable worsens the thermal stability of polymers. The most vulnerable bonds in polysulfones to the effects of water at processing temperatures were found.

Abstract: The series of compositions containing thermodynamically incompatible flexible blocks of aliphatic polyesters and rigid blocks of aromatic bis (urethane) imides in the volume of polymers was obtained on the basis of multiblock (segmented) poly (urethane-imides) and related aromatic polyimides. The series includes segmented poly (urethane-imides) with different relative content of flexible and rigid blocks, non-segregating mixtures of poly (urethane-imides) and thermoplastic partially crystalline polyimide, statistical copolymers of poly (urethane-imide) with imide, and non-segregating mixtures of statistical copolymers with thermoplastic polyimide. The derived polymer systems were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The deformation and strength properties of film samples are determined. It is shown that the properties of the studied polymers change as their content of imides blocks increases, and the transition from thermoplastic poly (urethane-imide) elastomers to thermoplastic polyimides is observed.

Abstract: In this paper, the tribological property of polyimide (PI) resin was improved by adding poly-p-phenylenebenzobisoxazole (PBO) fibers. The effects of PBO fiber volume fraction were studied by mechanics and tribology tests. The fracture and wear surfaces of PBO/PI composites were investigated by using scanning electron microscopy (SEM). The measurement showed that the flexural properties of composites reinforced by 10 vol% PBO fibers were lower than pure PI resin. With the increase of PBO fiber content, the flexural strength was first increase and then decrease. The frictional coefficient and wear rate of the PBO/PI composites varied with the variety of fiber content, and the optimum parameter was obtained at 20 vol%. The dominant wear mechanism and friction process were discussed on the basis of microscopic morphology analysis of wear surface of PBO/PI composite and the counterpart.