Synthesis and characterization of colorless polyimide nanocomposite films

A poly(amic acid) was prepared through the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 2,2′‐bis(trifluoromethyl) benzidine in N,N‐dimethylacetamide. Hybrid films were obtained from blend solutions of the precursor polymer and the organoclay dodecyltriphenylphosphonium–mica, with the organoclay content varying from 0 to 1.0 wt %. The cast films of poly(amic acid) were heat‐treated at different temperatures to create polyimide (PI) hybrid films. These PI hybrid films showed excellent optical transparency and were almost colorless. The intercalation of PI chains in the organoclay was examined with wide‐angle X‐ray diffraction and electron microscopy. In addition, the thermomechanical properties were tested with differential scanning calorimetry and thermogravimetric analysis, and the gas permeability was determined. The addition of only a small amount of the organoclay was sufficient to improve the thermal and mechanical properties of the PI, with the maximum enhancement being observed with 0.5 wt % organoclay. However, the water vapor permeability decreased with the clay loading increasing from 0 to 0.5 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The effect of curing history on the residual stress behavior of polyimide thin films

The effect of curing history on the residual stress behaviors in semiflexible structure poly(4,4′‐oxydiphenylene pyromellitimide) (PMDA–ODA) and rigid structure poly(p‐phenylene biphenyltetracarboximide) (BPDA–PDA) polyimide was investigated. Depending upon the curing history and different structures of polyimide, the residual stress behaviors and the morphology of polyimide thin films were detected in situ by using a wafer bending technique and wide angle X‐ray diffraction (WAXD), respectively. For the rigid structure BPDA–PDA polyimide, the residual stress and the slope decreased from 11.7 MPa and 0.058 MPa/°C to 4.2 MPa and 0.007 MPa/°C as the curing temperature increased, and the annealing process is done. However, for the semiflexible structure PMDA–ODA, the change of the residual stress and the slope was relatively not significant. In addition, it was found that the cured polyimide prepared at a higher temperature with a multistep curing process showed a higher order of chain in‐plain orientation and packing order than does the polyimide film prepared at a lower temperature with a one‐step curing process. These residual stress behaviors of polyimide thin films show good agreement with WAXD results, such as polyimide chain order, orientation, and intermolecular packing order, due to curing history. Specifically, it shows that the effect of curing history on residual stress as well as morphological change was significant in rigid BPDA–PDA polyimide but, not in semiflexible PMDA–ODA polyimide. Therefore, it suggests that the morphological structure depends upon curing history, and the polyimide backbone structure might be one of important factors to lead the low residual stress in polyimide thin films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3287–3298, 1999     

含脂肪链的聚酰亚胺单体对称醚二胺的合成

以对氯硝基苯和脂肪二醇为原料,在无水碳酸钾作用下经缩合和Pd/C催化氢化还原得到4个对称型聚酰亚胺二胺单体。以1,2-二(对氨基苯氧基)乙烷为例,考察了物料配比、碳酸钾用量、反应压力、催化剂用量等因素对收率的影响,得到了缩合反应较佳工艺条件为:乙二醇3.1 g,碳酸钾用量为15.9 g,乙二醇和对氯硝基苯的摩尔比为1∶2.5,反应时长24 h;还原反应的较佳工艺条件为:压力为0.6 MPa,催化剂用量为0.30 g,温度70℃。在该条件下,1,2-二(对氨基苯氧基)乙烷两步总收率为74.1%,其余3个二胺单体的合成收率在49.4%~65.7%。     

Research of aging test on high Tg colorless polyimide

For the past few years, colorless polyimide (CPI) has been drawn much attention for its application in transparent electronics. The high temperature (even to 450°C) process of the preparation of organic light-emitting diode display (OLED) device may have huge challenges on the properties of CPI, so we designed a series of aging test experiments to study the influence of test temperature and atmosphere on the high transparency percentages (Tr%) of CPI films with structure of Glass/SiO₂/CPI/SiO₂. As the aging temperature increased from 430 to 450°C and then to 470°C, the Tr% of the film decreased significantly. Comparing with the sample without aging, the transmission losses were 0.22%, 1.42%, and 4.82% for the films aging with 430, 450, and 470°C in N₂ atmosphere, respectively. Additionally, aging in nitrogen resulted in less Tr% loss (1.22%) compared with air (1.42%). This research offers insights into how to maintain the high Tr% of CPI films during high-temperature processing. Furthermore, it supports the development of more durable and reliable CPI-based components for OLED displays and other transparent electronic devices. This can lead to advancements in the performance of these devices, potentially extending their lifespan and broadening their range of applications.     

Synthesis and characterization of a low stress photosensitive polyimide

Use of polyimides with thermal coefficients of expansion comparable to that of the underlying substrate is critical to achieving low stress in microelectronic packaging applications. Photosensitive polyimides are finding increased use because of their significant reduction in device processing steps. A negative working photosensitive polyimide, based on the BPDA/PPD backbone, has been synthesized that incorporates these key features. The polyimide exhibits excellent photosensitivity and lithographic behavior, while retaining many thermal and physical properties of the polymer framework.     

新型含吡啶环芳香二胺及其可溶性聚酰亚胺的合成与表征

以苯甲醛和3-(4-硝基苯氧基)苯乙酮(NPAP)为原料,通过改进的Chichibabin反应制备了硝基化合物4-苯基-2,6-双[3-(4-硝基苯氧基)苯基]吡啶(PNPP),再用Pd/C和水合肼将PNPP进行还原,成功制备了一种新型含吡啶环的芳香二胺4-苯基-2,6-双[3-(4-胺基苯氧基)苯基]吡啶(PAPP)。以PAPP作为二胺,3,3′,4,4′-二苯醚四羧酸二酐(ODPA)作为二酐,N,N-二甲基甲酰胺(DMF)为溶剂,通过常规的两步法,经热或者化学亚胺化形成聚酰亚胺,制得了一种新型的含吡啶环聚酰亚胺。所得聚酰胺酸和聚酰亚胺的粘度分别为0.59 dL/g和0.56 dL/g。化学亚胺化所得的聚酰亚胺速溶于常见有机溶剂如DMF、N,N-二甲基乙酰胺(DMAc)、N-甲基-2-吡咯烷酮(NMP)、四氢呋喃(THF)等。制得了柔韧的聚酰亚胺膜,膜有很好的热稳定性,玻璃化转变温度(T_g)为230.8℃,氮气氛中10%失重温度为552.0℃,同时,膜还有较好的力学性能,拉伸强度为88.6 MPa,拉伸模量为1.04 GPa,断裂伸长率为8.7%,膜的吸水率为0.89%。     

Synthesis of well-dispersed polyimide/TiO2 nanohybrid films using a pyridine-containing aromatic diamine

The sol–gel fabrication of new well-dispersed polyimide (PI)/TiO₂ nanohybrid films is reported. The PI matrixes are synthesized via the polycondensation of pyromellitic dianhydride and a diamine monomer containing several constructive functional groups which introduced some interesting features to the final nanocomposite (NC) materials. The TiO₂–heteroatom interactions associated with the flexible characteristic of polymer backbone (which facilitates the stated interactions) have been led to the fabrication of well-dispersed nanoparticles with less than 100 nm in sizes, as confirmed by means of transmission electron microscopy. Thermal analysis techniques (TGA and DSC) have shown the superior thermal stability of fabricated NCs. The UV–Vis spectroscopy has illustrated a growing trend in the absorption efficiency along with the increase in TiO₂ contents. The created TiO₂ nanoparticles showed amorphous structures according to the X-ray diffraction patterns.     

Preparation and properties of soluble and colorless fluorine-containing photoreactive polyimide precursors

Photoreactive polyimide precursors, which are readily soluble in common organic solvents and optically transparent at light of 365 nm wavelength (i-line), similar to aliphatic polyimide precursors, were obtained by polycondensation of biphenyltetracarboxylic dianhydride (BPDA) and fluorine-containing diamine compounds. In particular, the polyimide precursor prepared from 2,2 bis(3-amino-4-methylphenyl) hexatluoropropane showed high solubility in common organic solvents and complete transparence at i-line wavelength. A 3 μm thick film of the polyimide precursor on a silicon wafer was exposed and developed, and offered high resolution (0.5μm line) patterns with an aspect ratio of 6.0. This polymide precursor swells very little in the developing solvent, resulting in the high resolution. Conversion of polyamic acid to polyimide at several curing temperatures was observed by infrared spectrophotometer and thermogravimetry.     

Functionalization of carbon nanofibers with diamine and polyimide oligmer

This paper discusses the functionalization of oxidized carbon nanofibers (OCNF) with monomer and oligmer that mimic the structure of repeat unit of a polyimide (2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-phenylene diamine). The goal was to covalently bind groups to the surface of OCNF that would both improve compatibility with the polyimide and potentially in case of the oligmer allow for chain entanglement in composite format. The reactions were carried out with or without initial activation by thionyl chloride (SOCl₂). Functionalization following each reaction step was characterized using thermal gravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). While quantitative analyzes indicated that the concentration of surface reactive oxygen groups was fairly low, the OCNFs were successfully functionalized with the aromatic diamine, dianhydride and the polyimide oligmer.     

Structure effect on water diffusion and hygroscopic stress in polyimide films

A bending-beam technique has been used to in situ monitor the diffusion of water in various polyimide films. The polyimides studied are pyromellitic dianhydride-4.4′-oxydianiline (PMDA–ODA), pyromellitic dianhydride-p-phenylenediamine (PMDA–PDA), and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride-p-phenylenediamine (BPDA–PDA), and their blends and random copolymers. The diffusion of water in these films obeys Fick's law. In PMDA–ODA, the mean diffusion constant is 5.2 ± 0.4 × 10^?9 (cm²/s) for thicknesses ranging from 6.7 to 27.3 μm. In PMDA–PDA, it is 2.0 ± 0.4 × 10^?9 (cm²/s) for thicknesses ranging from 7.3 to 20.0 μm, and in BPDA–PDA, 0.27 ± 0.02 × 10^?9 (cm²/s) for thicknesses ranging from 4.8 to 21.0 μm. In the blends and random copolymer with 50 wt % PMDA–ODA and 50 wt % PMDA–PDA, the diffusion constants are slightly smaller than those in the pure PMDA–ODA, but much larger than in the pure PMDA–PDA. On the contrary, in those with 50 wt % BPDA–PDA and 50 wt % PMDA–PDA, the diffusion constants are much smaller than those in the pure PMDA–PDA, but slightly larger than in the pure BPDA–PDA. These diffusion constants are primarily affected by the chemical structure of the imide molecule. The morphology, such as crystallinity, of the films has played a secondary factor. Hygroscopic stresses due to water uptake in all the studied films increase as the film thickness increases. It can be attributed to that the film orientation decreases with the increase of thickness.     

Surface reactivity of polyimide and its effect on adhesion to epoxy

Polyimides are commonly used as organic passivation layers for microelectronic devices due to their unique combination of properties such as low dielectric constant, high thermal stability, excellent mechanical properties and superior solvent resistance. Unfortunately, polyimides are well known to be difficult to bond to other materials, especially to epoxy resins. Many surface treatments have been developed to increase epoxy–polyimide adhesion. These treatments include exposure to ion beams, plasmas and chemical solutions. The goal of our research was to relate surface reactivity of epoxy and polyimide resins to the strength of epoxy–polyimide interfaces. The surface reactivity of four polyimides was studied and quantified using contact angle measurements, flow microcalorimetry (FMC), Fourier transform infrared (FT-IR) spectroscopy (using an attenuated total reflection (ATR) accessory) and X-ray photoelectron spectroscopy (XPS). Several ways of analyzing contact angles were tried and only a weak correlation between the polar component or the acid–base components of the surface free energy with the critical interfacial strain energy release rate (i.e., the interfacial fracture strength) was observed. FMC results suggest that the strength of epoxy–polyimide interfaces is related to the molecular interactions between the curing agent and polyimide. The molecular interactions between the curing agent and polyimide surfaces were found to be either greater than epoxy and polyimide interactions or more irreversible. Therefore, the curing agent (2,4-EMI) is thought to play a critical role in controlling adhesion strength.     

Barrier and thermal properties of polyimide derived from a diamine monomer containing a rigid planar moiety

An aromatic polyimide (3,6‐CPI ) was prepared by the polymerization of pyromellitic dianhydride and diamine (3,6‐CDA ) containing a rigid planar carbazole moiety. The synthesized polyimide shows outstanding barrier properties with oxygen permeation rate and water vapor permeation rate low at 7.9 cm³ m^?2 day^?1 and 9.8 g m^?2 day^?1, respectively. Wide angle X‐ray diffraction, positron annihilation lifetime spectroscopy and molecular dynamics simulations reveal that the excellent barrier properties of 3,6‐CPI are mainly due to the crystallinity and low free volume of the polymer, which result from the rigid planar backbone structure and strong interchain hydrogen bonding. In addition, the polyimide exhibits excellent thermal stability and favorable mechanical properties with a 5 wt% weight‐loss temperature of 559 °C in nitrogen, a glass transition temperature (T _g) of 397 °C and a tensile strength of 115.4 MPa . The as‐synthesized polyimide shows potential packaging applications in the field of flexible electronics and displays, flexible and thin film photovoltaics, and light‐emitting diodes. © 2017 Society of Chemical Industry     

一种新型渣油降粘剂的制备及评价

研究以自制的丙烯酸十八醇醚酯单体(A)、马来酸酐(M)、苯乙烯(S)为单体进行共聚反应,制得一种油溶性稠油降粘剂AMS。确定了AMS合成的最佳条件:丙烯酸十八醇醚酯、苯乙烯、马来酸酐摩尔比为5∶1∶3,反应温度为90℃,引发剂BPO用量为0.6%,反应时间为6 h。结果表明,在温度为50℃时,降黏剂AMS加量为0.6%时对渣油的降粘率达到54.11%。此外,加入0.2%助剂Span-80能进一步提高AMS降粘效果,当剪切速率为2 000 r/min时AMS的降粘效果可达90%以上。     

一种新型渣油降粘剂的制备及评价

研究以自制的丙烯酸十八醇醚酯单体(A)、马来酸酐(M)、苯乙烯(S)为单体进行共聚反应,制得一种油溶性稠油降粘剂AMS。确定了AMS合成的最佳条件:丙烯酸十八醇醚酯、苯乙烯、马来酸酐摩尔比为5∶1∶3,反应温度为90℃,引发剂BPO用量为0.6%,反应时间为6 h。结果表明,在温度为50℃时,降黏剂AMS加量为0.6%时对渣油的降粘率达到54.11%。此外,加入0.2%助剂Span-80能进一步提高AMS降粘效果,当剪切速率为2 000 r/min时AMS的降粘效果可达90%以上。     

Synthesis and characterization of organo‐soluble polyimides derived from a new spirobifluorene diamine

Polyimides exhibit outstanding thermal and thermo‐oxidative stability, excellent solvent resistance, good mechanical and electrical properties and superior chemical resistance. However, their practical applications are frequently limited by their infusible and insoluble nature. Structural modifications of the polymer backbone have been utilized to modify polyimide properties, either by reducing the interaction or by reducing the stiffness of the polymer backbone. Novel organo‐soluble polyimides containing spirobifluorene units were synthesized by the polycondensation of 2,7‐bis‐amino‐2′,7′‐di‐t‐butyl‐9,9′‐spirobifluorene with three aromatic dianhydrides. The one‐step polymerization procedure was conducted at 200 °C in m‐cresol, and the structures of the resulting polyimides were confirmed using infrared and NMR spectroscopy. The weight‐average molecular weights and polydispersities of the resulting polymers were in the ranges 20 600–341 000 and 1.02–1.30, respectively. The glass transition temperatures of the polyimides were in the range 289–322 °C, and the 10% weight loss in nitrogen appeared at a temperature higher than 435 °C and the residual weight at 800 °C was above 58%. The spiro segment has been introduced into polyimides, resulting in amorphous polyimides, conferring on them an enhanced solubility and leading to a significant increase in both glass transition temperature and thermal stability. These types of materials have potential for many applications. Copyright © 2010 Society of Chemical Industry     

以生物基二聚二胺,BPADA,m-PDA为单体的PI的合成

以双酚A型二醚二酐、生物基二聚二胺、间苯二胺为原料,间甲酚为溶剂,采用传统的一步法合成了一系列生物基共聚及均聚聚酰亚胺,利用傅里叶变换红外光谱仪、凝胶渗透色谱仪、差示扫描量热仪、热重分析仪等表征了生物基聚酰亚胺的结构并分析了其热性能和力学性能。结果表明:所制聚酰亚胺的玻璃化转变温度为26~215℃,质量损失5%时的温度为436~512℃;随着二聚二胺用量的增加,聚酰亚胺的断裂拉伸应变显著提高,二聚二胺摩尔分数为50%时,断裂拉伸应变达507%。     

聚酰亚胺的合成和应用

简要地介绍了4种聚酰亚胺的聚合法(熔融缩聚、溶液缩聚、界面缩聚及气相沉积法),并对这4种方法进行了比较和评述,对聚酰亚胺的应用作了简要介绍。     

Synthesis of poly(p‐phenylene diamine) and its corrosion inhibition effect on iron in 1M HCl

Water‐soluble poly(p‐phenylene diamine) was chemically synthesized. Its corrosion inhibition performance was evaluated for iron corrosion in 1M HCl at various concentrations, and the results were compared with that of the monomer. The corrosion inhibition properties were evaluated by polarization techniques and electrochemical impedance spectroscopy. The results showed that poly(p‐phenylene diamine) was a more efficient corrosion inhibitor than the monomer and gave an 85% inhibition efficiency at a concentration of 50 ppm, whereas the monomer gave an efficiency of 73% at 5000 ppm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Residual stress effect on degradation of polyimide under simulated hypervelocity space debris and atomic oxygen

Polyimides are used as the outer layer of thermal control insulation blankets covering most of the external spacecraft surfaces that are exposed to space environment. The combined effect of ground simulated hypervelocity space debris impacts and atomic oxygen (AO) on the fracture of polyimide films was studied. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km/s. The impacted films were exposed to an RF plasma source, which was used to simulate the effect of AO in the low Earth orbit. Scanning electron microscopy and atomic force microscopy were used to characterize the fracture and surface morphology. When exposed to oxygen RF plasma, the impacted polyimide film revealed a large increase in the erosion rate, the damage being characterized mainly by the formation of new holes. This effect is explained by the formation of residual stresses due to the impact and enhancement of oxygen diffusivity and accumulation. A complementary experiment, in which a stressed polyimide was exposed to RF plasma, supports this model. This study demonstrates a synergistic effect of the space environment components on polymers' degradation, which is essential for understanding the potential hazards of ultrahigh velocity impacts and AO erosion for completing a successful spacecraft mission.     

The effect of local residual stress on the fractal dimension of silicate glasses

Local residual stress caused by impacts, machining and indentation results in a decrease in strength in most materials that fail in a brittle manner. The ratio of the critical crack size, c, and the fracture mirror size, r, also is affected by the existence of local residual stress. The global fracture toughness of non-R curve materials is not affected by the local residual stress. The fractal dimension of the fracture surface as characterized by the fractal dimensional increment, D*, is directly related to the square of the fracture toughness. This paper addresses the question of the effect of the local residual stress on the fractal dimension of the fracture surface. We derive a relationship between the fractal dimensional increment and the c/r ratio for materials fractured with and without local residual stress. We then compare the prediction with two cases of experimental results. We show the fractal dimension remains constant with the change in the c/r ratio for local residual stress conditions.