Tuning the aggregation of polyimide thin films by modification of their molecular interactions

Thin films of an organo‐soluble polyimide based on 1,4‐(3,4‐dicarboxyphenoxy)benzene dianhydride (HQDPA) and 2,2′‐dimethyl‐4,4′‐methylene dianiline (DMMDA) have been studied. A prism coupler was used to measure the refractive indices. The average refractive indices of thin films prepared by annealing at different temperatures and times were chosen to characterize the condensation states of thin films. Thin films annealed at 200 °C show irreversible changes in physical properties, eg solubility. FTIR spectroscopy showed that the chain structures of the above thin films remained unchanged. It is proposed that specific molecular interactions induce the irreversible changes revealed by fluorescence spectroscopy. © 2000 Society of Chemical Industry     

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     

Preparation and characterization of magnetic polyimide hybrid thin films

Magnetic polyimide hybrid thin films were synthesized from pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA), and Fe₃O₄ magnetic nanoparticles via thermal imidiazation in nitrogen environments. The magnetic polyimide hybrid thin films were analyzed and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The magnetic properties of magnetic nanoparticles and polymer hybrid thin films were assessed using a vibrating sample magnetometer (VSM), and the physical properties of hybrid thin films were tested. Results revealed that the magnetic polyimide hybrid thin films had superparamagnetic behavior and excellent mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Water diffusion studies in polyimide thin films

The water diffusion behaviors and activation energies of PDA- and ODA-based polyimide thin films were quite dependent on both the chemical structure and the morphological structure in the films. The water diffusion coefficients of polyimide thin films increased with increasing temperature. The activation energies varied in the range of 5.81 to 9.27 kcal/mol and were relatively higher for the PDA-based polyimide thin films than for the corresponding ODA-based polyimide thin films. For the PDA- and ODA-based polyimide films, the differences in the morphological structures and the chemical affinity to water molecules might be reflected directly on the water diffusion behaviors. The PDA-based polyimide films exhibited a relatively more ordered morphological structure (high crystallinity and good in-plane orientation) than that of the corresponding ODA-based polyimide thin films, which may serve as impenetrable obstacles for the water diffusion in the out-of-plane direction. Consequently, it may lead to a relatively slower water diffusion and high activation energy in the PDA-based polyimide thin films. Additionally, the PDA-based polyimide films with relatively lower chemical affinity showed relatively low diffusion coefficients and high activation energies. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 731–737, 2001     

均苯型共聚聚酰亚胺薄膜的制备及其性能

以2,2′-双[3-苯基-4(4-氨基苯氧基)苯基]丙烷(BPAPOPP)、4,4′-二胺基二苯醚和均苯四甲酸酐为原料,采用两步法共缩聚制备了一系列共聚聚酰亚胺薄膜.采用红外光谱仪、差示扫描量热仪等分析了薄膜的结构,利用静态热机械分析仪分析了薄膜的性能.结果表明:制备的聚酰亚胺薄膜具有较低的玻璃化转变温度;随着BPAP...     

Dielectric and conduction properties of pure polyimide films

Capacitors with an Al–polyimide–Al sandwich film structure have been fabricated: the top and the bottom aluminium electrodes were deposited by vacuum evaporation and the polyimide film was deposited by an isothermal immersion method. An X‐ray diffractogram of the film indicates the amorphous nature of the polyimide film. Dielectric and ac conduction properties of polyimide capacitors in the frequency range 10 kHz to 10 MHz at various temperatures (303–423 K) are reported; the dc conduction at different voltages and at various temperatures (303–423 K) is given. The capacitance of the film decreases with increasing frequency but increases with increasing temperature. The ac conduction studies suggest that electron hopping is responsible for conduction while the dc conduction studies reveal that Poole–Frenkel conduction is predominant at high fields. The activation and zero field activation energies are also calculated. © 2001 Society of Chemical Industry     

Construction of fluorenyl-modified low dielectric constant polyimide films with excellent mechanical properties and optical transparency

In order to meet the requirements of highly integrated and miniaturized electronic components, there is an urgent need for low dielectric materials with high mechanical properties and optical transparency in the field of microelectronics. In this study, a series of novel polyimide films (FPI) containing fluorenyl were prepared, and the effects of the fluorenyl content on the thermal, mechanical, and dielectric properties of the copolymerized films were investigated and discussed. The results demonstrate a significant decrease in the dielectric constant of the FPI films following the introduction of fluorenyl into polyimide (PI) chain segment. The FPI films also exhibited high mechanical properties, including tensile strengths between 92 and 106 MPa and elongation at break in the range of 8.4%–13.0%. Additionally, the introduction of the noncoplanar fluorenyl considerably improved the optical transparency and solubility of the FPI film. It is noteworthy that the FPI-3 has the best dielectric properties, with a low dielectric constant of 2.61 at 10 MHz and shows low water absorption (0.49%). The results show that we have prepared a novel low dielectric PI material film with excellent mechanical properties and optical transparency by introducing fluorenyl into the PI chain segment. These FPI films with satisfactory properties may be good candidates for dielectric materials for electronic components.     

Stresses associated with diffusion in polyimide and polyacrylics films

When a constrained polymeric thin film is immersed in a liquid medium, its state of stress changes because the diffusion of the liquid into the film causes it to swell. Polyimide and polyacrylics films are used in the laminated structures of inkjet printheads. Swelling behavior of the films in various ink component solutions are of great interest because they are closely related to the delamination problem. Swelling stress at constant strain was measured using an environmental tensile tester at both ambient and elevated temperatures. Two kinds of information were extracted. One is the extent of stress relaxation, which is the amount of stress decay between initial stress and equilibrium stress. The difference in the extent of stress relaxation could result in delamination if two different materials with different swelling characteristics are bonded together and exposed to a swelling agent. The other piece of information was the diffusion coefficients of the liquid agents into the polymer films. The magnitude of the diffusion coefficient indicates the rate of proceeding by the penetrant, i.e., the rate of swelling of the films. The results show that the extent of stress relaxation and diffusivity are different for two films. In addition, the diffusion in polyimide film is Fickian and the diffusion in polyacrylics film is pseudo‐Fickian. The changes in mechanical properties after swelling also differ. Among all the ink solutions tested, one component was identified as the most influential and detrimental agent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

纳米二氧化锆改性聚酰亚胺薄膜的制备及性能

聚酰亚胺（PI）在工程高分子材料领域广受关注,开发新型耐高温、疏水性良好的PI薄膜材料是推动高性能高分子材料在电动汽车等高新技术领域工程化应用的重要突破口。以间苯二胺（MPD）与4,4’-(4,4’-异丙基二苯氧基)二酞酸酐（BPADA）为原料,采用原位掺杂热亚胺化合成PI薄膜,通过向聚酰胺酸（PAA）前驱液中添加纳米ZrO2粉体对聚酰亚胺薄膜进行改性,制得不同ZrO2添加量（0.77%～1.93%,以MPD、BPADA总质量为基准,下同）的复合型PI薄膜。借助XRD、SEM、EDS、FTIR及TGA对复合薄膜进行了结构和形貌表征。结果表明,与纯PI相比,ZrO2添加量为1.93%的复合薄膜初始分解温度为415℃（提高5%）,水接触角为91.7°（提高61%）,表明ZrO2对改善PI薄膜的性能具有重要作用。     

纳米二氧化锆改性聚酰亚胺薄膜的制备及性能研究

聚酰亚胺在工程高分子材料领域广受关注,开发新型耐高温、疏水性良好的聚酰亚胺薄膜材料是推动高性能高分子材料在电动汽车等高新技术领域工程化应用的重要突破口。本工作采用两步法合成复合型聚酰亚胺薄膜,通过纳米ZrO2粉体对聚酰亚胺薄膜进行改性,借助XRD、SEM、能谱、红外光谱等手段对复合薄膜进行结构和形貌的表征,并测试了复合薄膜的热稳定性、疏水性及抗拉强度,结果表明纳米ZrO2的加入增强了聚酰亚胺分子链之间的相互作用,使其耐热性能得到显著提高,分解温度可以提高20 ℃,复合薄膜的水接触角提高60%,疏水性能得到提高。本工作为开发新型高性能聚酰亚胺高分子材料提供了新的思路。     

Study on morphology control and how to affect mechanical properties of polyimide/silica hybrid films

A series of polyimide (PI)/silica hybrid films were prepared by sol–gel method, using hydrolyzed tetraethoxysilane and poly amic acid‐imides (PAA‐Is), which were different imidization degree controlled by chemical imidization method. The imidization degree was characterized by Fourier transform infrared spectra and their corresponding morphology was characterized by scanning electron microscopy. The results show that there are two kinds of silica particles and their formative morphology obeys the double phase separation mechanism. According to the increase of PAA‐I imidization degree, amount of nano silica particles decreased and the diameter of macro silica particles increased in the hybrid films. Tensile testing, dynamic mechanical analysis, and thermal mechanical analysis results show that, according to the amount of nano silica particles increasing, the hybrids have the higher the mechanical properties, glass transition temperature (T_g), and thermal expansion coefficient. Through controlling PI/silica hybrid films microstructure, its mechanical properties can be controlled. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Residual stress and thermal expansion of spun-on polyimide films

The residual stress in spin coated films and the effect of heat treatments on this stress were determined by the Fizeau interference method. Three types of spin coated polyimide (PI) films have been studied. Two of them were prepared by thermal conversion of their poly(amic acid)s (PAAs) and the third one by solvent evaporation of the soluble preimidized PI. For the imidized PI films the residual stress vs. bake temperature shows an inclined steplike behavior while this function for soluble PI is approximately linear. The room temperature stress relative to silicon substrates in fully baked films (400°C) is between 40 and 70 MPa and nearly independent of the film thickness. From the stress measurement, the thermal expansion coefficient and Young's moduli have also been obtained. The thermal expansion coefficient and the Young's modulus are in the order of 9.0 × 10^?6°C^?1 and 10 GPa, respectively. These values deviate from those published for bulk material which is explained by the in-plane orientation of the molecular chains in spun-on PI films.     

Water sorption behaviors of the BPDA‐based polyimide films depending upon the structural isomers of diamine

For the biphenyltetracarboxylic dianhydride (BPDA)‐based polyimide thin films, the water sorption behaviors were gravimetrically investigated by using a thin film diffusion analyzer. The water sorption behaviors of the polyimide thin films are quite different and strongly dependent upon the sort of polyimide. The diffusion coefficients of the polyimide thin films vary in the range of 1.6 × 10⁻¹⁰ to 12.4 × 10⁻¹⁰cm²/s and the water uptakes vary from 1.52 to 5.25 wt %. Both the diffusion coefficient and water uptake of the polyimide thin films are in the increasing order: BPDA‐pPDA < BPDA‐p,p′ODA < BPDA‐p,m′ODA < BPDA‐mPDA ∼ BPDA‐p,p′DDS < BPDA‐m,m′DDS. Specifically, the polyimide films with para‐oriented linkages in backbone structure showed relatively lower diffusion coefficient and water uptake than the corresponding polyimide films with meta‐oriented linkages because of the well‐developed crystalline structure and good intermolecular chain ordering. In addition, the polyimide thin films having higher chain order showed relatively lower diffusion coefficient and water uptake. The crystallinity and intermolecular chain ordering in the morphological structure are critical parameters in controlling the water sorption behaviors of the polyimide thin films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2121–2127, 2001     

Microstructure and properties of new polyimide/polysiloxane composite films

A series of novel polyimide/polydiphenylsiloxane) (PI/PDDS) composite films with different contents of DDS were prepared using sol–gel method. The noncrosslinked PI–DDS and crosslinked PIS–DDS were synthesized through cohydrolysis and condensation between DDS and polyamic acid (PAA) or aminopropyltriethoxysilane(APTES)‐terminated polyamic acid (PAAS). All the composite films have high thermal stability near pure PI. Field emission scanning electron microscopy (FE‐SEM) study shows that the polysiloxane from hydrolyzed DDS well dispersed in polyimide matrix, without macroscopic separation for the composite films with low content of DDS, while large domain of polysiloxane was formed in films with high DDS content. The microstructure of composite films is in accordance with the transparency of corresponding films. X‐ray study shows the PDDS is amorphous in PI matrix. The introduction of DDS into PI can improve the elongation at break and at the same time, the composite films still remained with higher modulus and tensile strength. The density and water absorption of the composite films decreased with the increasing DDS content. The composite films with DDS content below 10 wt % exhibit good solvent resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 124–132, 2006     

Preparation and properties of ternary polyimide/SiO2/polydiphenylsiloxane composite films

A series of novel ternary polyimide/SiO₂/polydiphenylsiloxane (PI/SiO₂/PDPhS) composite films were prepared through co‐hydrolysis and condensation between tetramethoxysilane, diphenyldimethoxysilane (DDS) and aminopropyltriethoxysilane‐terminated polyamic acid, using an in situ sol–gel method. The composite films exhibited good optical transparency up to 30 wt% of total content of DDS and SiO₂. SEM analysis showed that the PDPhS and SiO₂ were well dispersed in the PI matrix without macroscopic separation of the composite films. TGA analysis indicated that the introduction of SiO₂ could improve the thermal stability of the composite films. Dynamic mechanical thermal analysis showed that the composite films with low DDS content (5 wt%) had a higher glass transition temperature (T_g) than pure PI matrix. When the content of DDS was above 10 wt%, the T_g of the composite decreased slightly due to the plasticizing effect of flexible PDPhS linkages on the rigid PI chains. The composite films with high SiO₂ content exhibited higher values of storage modulus. Tensile measurements also showed that the modulus and tensile strength of the composite films increased with increasing SiO₂ content, and the composite films still retained a high elongation at break due the introduction of DDS. The density and water absorption of the composite films were also characterized. Copyright © 2006 Society of Chemical Industry     

Colorless polyimide nanocomposite films: Thermomechanical properties,morphology, and optical transparency

Polyimide (PI)/organoclay hybrid films were prepared by the solution intercalation method, using dodecyltriphenylphosphonium‐mica (C₁₂PPh‐Mica) as the organoclay. The variations with organoclay content of the thermomechanical properties, morphology, and optical transparency of the hybrids were examined for concentrations from 0 to 1.0 wt %. For low clay contents (≤ 0.5 wt %), the clay particles are better dispersed in the matrix polymer, without the formation of large agglomerates of particles, than they are for high clay contents. However, agglomerated structures form and become denser in the PI matrix for clay contents ≥ 0.75 wt %. This is in agreement with the observed trends in the thermomechanical properties and the optical transparency, which worsen drastically when the clay content of the C₁₂PPh‐Mica/PI hybrids reaches 0.75 wt %. However, when the amount of organoclay in the hybrid is 0.75 wt %, the initial modulus of the hybrid film is at its maximum value. The PI hybrid films were found to exhibit excellent optical transparencies and to be almost colorless. It was found, however, that the transparency decreases slightly with increases in the organoclay content because of agglomeration of the clay particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

高温热处理对聚酰亚胺薄膜性能的影响

研究了高温热处理对聚酰亚胺(PI)薄膜拉伸性能和热性能的影响。在薄膜完全环化后,随着热处理温度的升高,薄膜的拉伸强度、弹性模量先增大后基本保持不变,断裂伸长率先保持不变后明显降低,热膨胀系数也显著降低,而薄膜的玻璃化转变温度略有增大。高温热处理工艺可制备高强度和低热膨胀系数的高性能PI薄膜。     

Dielectric properties and energy-storage performance of two-dimensional molybdenum disulfide nanosheets/polyimide composite films

Flexible dielectric materials with high electric energy density and high-temperature resistant characteristic are of great importance for modern electronics and electrical systems. Herein, two-dimensional molybdenum disulfide (MoS₂) nanosheets were efficiently produced via liquid-phase exfoliation and then incorporated into polyimide (PI) to prepare MoS₂/PI dielectric nanocomposites. Compared to the pristine PI, MoS₂/PI nanocomposite films exhibited much larger dielectric permittivity while their dielectric losses still maintained relatively low levels. On the other hand, the Weibull breakdown strength of these nanocomposite films initially increased and then decreased with the increase in the MoS₂ content and gave rise to a maximum value of 395 MV m⁻¹ at 1 vol % loading. Combination of the improved dielectric permittivity and breakdown strength makes the MoS₂/PI nanocomposite film with 1 vol % MoS₂ possess an elevated energy density of about 3.35 J cm⁻³. Moreover, good tensile and thermal properties of the nanocomposite films hold great promise for their applications in high-temperature and harsh conditions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47991.     

Water‐sorption behavior of P‐phenylene diamine–based polyimide thin films

Four different p‐PDA–based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400°C: poly(p‐phenylene pyromellitimide) (PMDA‐PDA); poly(p‐phenylene biphenyltetra carboximide) (BPDA‐PDA); poly(p‐phenylene 3,3′,4,4′‐oxydiphthalimide) (ODPA‐PDA); and poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide) (6FDA‐PDA). Water‐sorption behaviors of polyimide films were gravimetrically investigated at 25°C and 22–100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 × 10⁻¹⁰ cm²/s, and are in the increasing order: BPDA‐PDA < PMDA‐PDA ∼ ODPA‐PDA < 6FDA‐PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA‐PDA < ODPA‐PDA < 6FDA‐PDA < PMDA‐PDA. The water‐sorption behaviors for the p‐PDA–based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p‐PDA–based polyimide thin films are closely related to the in‐plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1315–1323, 2000