A series of polyimide/zirconia (PI/ZrO2) hybrid films were synthesized based on zirconium n-butoxide, pyromellitic acid dianhydride (PMDA) and 4,4′-oxydianiline (ODA) by a sol-gel process. The atomic oxygen (AO) exposure tests were carried out using a ground-based atomic oxygen effects simulation facility. The effects of ZrO2 content on the morphology and structure evolvement of PI/ZrO2 hybrid films were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectrometer (XPS), respectively. The results indicated that a zirconia-rich layer was formed on the polyimide film sourcing from the zirconium n-butoxide after AO exposure, which decreased the erosion rate and obviously improved the AO resistance of polyimide films. 相似文献
Ternary hybrid nanocomposites of polyimide (PI), poly(vinylsilsesquioxane) (PVSSQ), and titania (PI/PVSSQ/Ti) were prepared by thermal imidization from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA)-4,4'-oxydianiline (ODA) polyamic acid (BPDA–ODA PAA) and a sol-gel process from vinyltriethoxysilane(VSSQ) and titanium isopropoxide(Ti(OPr)4). The microstructure, interfacial interaction, and optical and thermo-mechanical properties of the hybrid films have been investigated. The phase morphology and the properties are influenced by the composition of PVSSQ and titania. For the PI/VSSQ/titania ternary hybrid systems, the particle size is significantly decreased and the inorganic particles are extremely finely distributed in the nanometer scale, suggesting that the interaction between the particles and the matrix increases. It is concluded that the addition of titania plays a compatibilizing role for the PI/PVSSQ binary hybrids, resulting in the enhancement of optical transparencies and thermo-mechanical properties of the binary hybrids. 相似文献
We present molecular dynamics simulations of pseudo hard sphere fluid (generalized WCA potential with exponents (50, 49) proposed by Jover et al. [J. Chem. Phys 137, (2012)] using GROMACS package. The equation of state and radial distribution functions at contact are obtained from simulations and compared to the available theory of true hard spheres (HS) and available data on pseudo hard spheres. The comparison shows agreements with data by Jover et al. and the Carnahan–Starling equation of HS. The shear viscosity is obtained from the simulations and compared to the Enskog expression and previous HS simulations. It is demonstrated that the PHS potential reproduces the HS shear viscosity accurately. 相似文献
A series of polyimide (PI)-silica hybrid nanocomposites are prepared from 3,3′,4,4′biphenyltetracarboxylic dianhydride (BPDA)-4,4′-oxydianiline (ODA) polyamic acid (PAA) and tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) by the sol-gel process. 3-Aminopropyltriethoxysilane (3-APS) is used to enhance the interfacial interaction between polyimide and silica. The morphology, interfacial interaction, and properties of the hybrids are investigated using scanning electron microscope (SEM), UV-vis spectroscopy, atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). SEM and AFM images indicate that silica particles of ca. 45-55 nm size are uniformly distributed in polyimide matrices and that the interfacial interaction between PI and TEOS is better than that between PI and TMOS. The optical transparencies of the PI/TEOS hybrids are better than that of the PI/TMOS hybrids. FTIR spectra confirm the Si O Si bond as well as the conversion of PAA to polyimide and PI/silica hybrid films. The thermal stability is increased after incorporation of the silicas in the polyimide matrix. 相似文献
A new diamine monomer 2,2-bis[4-(3-aminophenoxy)phenyl]propane (3-BAPOPP) was synthesized through two steps and its melting point was determined by differential scanning calorimetry (DSC). It was then copolymerized with 4,4′-oxydianiline (44ODA) and 4,4′-oxydiphthalic anhydride (ODPA) to obtain a series of aromatic polyimide(3-BAPOPP/44ODA/ODPA-PI) films. Fourier transform infrared (FT-IR) was used to characterize the structures of the monomer and the polyimide films. Water absorption, ultraviolet-visible (UV-Vis) spectroscopy, contact angle, DSC, and thermo-gravimetric analysis (TGA) were used to characterize the properties of 3-BAPOPP/44ODA/ODPA-P films. The results showed that the PI films had low water absorption in the range of 1.5%~1.9%, low surface energy in the range of 43.3 ~43.5 mJ/m2, glass transition temperature (Tg) in the range of 192.5°C~226.1°C, and dielectric constant in the range of 2.79~3.02 at 1 MHz. The films also exhibited good thermal properties and good optical properties, with the ultra violet cut-off wavelength being in the range of 346~364 nm. 相似文献
By means of electron microscopy, the spatial correlation of gold nanoparticles are studied, obtained by thermal vacuum sputtering of metal on a bromine-activated surface of films of adamantane-containing polyimides and copolyimides based on pyromellitic anhydride (PMDA), 4,4'-oxydianiline (ODA), and 1-aminoethyl-3-(4'-aminophenyl)adamantane (AEAPhA) or 3,4,3',4'-tetracarboxydiphenyloxide dianhydride (ODPA), ODA, and AEAPhA with varying ratio of ODA and AEAPhA fragments. It is shown that with increasing ratio of mole fractions [AEAPhA]/[ODA], the texture of the film surface, free volume, the correlation length, and the frequency of alternation of the particle distribution density change. The shortrange order decreases, while the long-range order increases in ensembles of particles. The supramolecular structure of the polymer is transformed similarly because of structural transitions in the amorphous state of ODPA–ODA–AEAPhA and the mesomorphic state of PMDA–ODA–AEAPhA.
A combined wide angle X‐ray diffraction (WAXD)/small‐angle X‐ray scattering (SAXS)/scanning electron microscopy (SEM)/density study of structure and morphology was carried out for a large series of pyromellitic dianhydride‐oxydianiline (PMDA‐ODA) polyimide (PI) samples processed using different powder metallurgy techniques. Using a combined DSC/creep rate spectroscopy (CRS)/long‐term creep resistance (LTCR) approach, their molecular dynamics, thermal and elastic properties, and creep resistance in the temperature range from 20 to 470°C were also studied. Both a choice of the method of formation of fine PI particles and the order of applying high pressure relative to high temperature to form the monolithic samples led to the observation of significant property differences. Relationships between the processing conditions, structure, and properties were determined. As a result, the conditions for optimizing certain PMDA‐ODA polyimide properties, especially creep resistance and elastic properties at extreme temperatures, were determined. 相似文献
A polymer nanohybrid material with enhanced dielectric permittivity was prepared using the fluorine‐containing polyimide (PI) 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride/4,4′‐oxydianiline (6FDA/ODA) as matrix and graphene as conductive filler in our present work. Studies on the dielectric properties of the 6FDA/ODA–graphene nanohybrid films show that the dielectric permittivity (ε) can be significantly enhanced by the layer‐by‐layer structure of graphene and the presence of fluorine also has an important influence on the improvement of ε. The percolation theory and microcapacitor model are used to explain the change of dielectric properties and a percolation threshold fc = 0.0152 (2.45 wt%) was obtained by a linear‐fit calculation.
An amino-functionalized montmorillonite (APTMS-MMT) was prepared by the grafting of 3-aminopropyltrimethoxysilane (APTMS) on the surface of MMT via the ultrasonic synthesis process and characterized by a variety of techniques: FT-IR, thermogravimetic analysis (TGA), particles size analysis and ζ-potential measurement. The results showed the size and size distribution of APTMS-MMT particles were decreased, and the ζ-potential of particles was increased obviously via the ultrasonic synthesis process. The particles of 30% APTMS-MMTUS (MMT modified with 30 wt% APTMS with ultrasonic synthesis process) had a z-average diameter of about 500 nm and a polydispersity index of 0.2. The resultant 30% APTMS-MMTUS was dispersed uniformly and stably in water. The poly(acrylic acid) (PAA)/APTMS-MMT multilayer films were grown through layer-by-layer (LBL) deposition of PAA and APTMS-MMT. SEM results indicated that the ultrasonic synthesis of APTMS-MMT increased dispersability of clay sheets at high loadings. The thermal stability and mechanical properties of PAA/APTMS-MMT composites were investigated by TGA and tensile test respectively. The results showed the ultrasonic synthesis of APTMS-MMT enhanced the thermal stability and mechanical properties of PAA/APTMS-MMT composites significantly. PAA/30% APTMS-MMTUS composite displayed 3 times higher strength and 6 times higher Young's modulus when compared with pure PAA polymer. 相似文献
The molecular orientation of adsorbed polyimides and model compounds with respect to highly oriented pyrolytic graphite (HOPG) surfaces was determined by reflection-absorption infrared (RAIR) spectroscopy. As the thickness of the pyromellitic diimide (PMDI) films decreased, bands near 766 and 729 cm-1, which were assigned to the CNC out-of-plane bending modes, were relatively strong in the spectra, demonstrating that PMDI was adsorbed flat-down with the imide rings parallel to the HOPG surface. As the thickness of the N,N'-diphenylpyromellitic diimide (DPPMDI) films was decreased, bands near 1785 and 1722 cm-1 which were assigned to the C=O stretching modes, were relatively strong in the RAIR spectra. Moreover, bands near 869, 841, 742, and 686 cm-1 attributed to the out-of-plane bending modes of monosubstituted benzene rings became considerably stronger. It was suggested that the DPPMDI molecules nearest to the HOPG surface were adsorbed edge-on with the carbonyl groups perpendicular to the surface and with the monosubstituted benzene rings parallel to the surface. There were significant differences in relative band intensity observed between the transmission and RAIR spectra of polyimides derived from pyromellitic dianhydride (PMDA) and oxydianiline (ODA). The band near 1725 cm-1 due to the C=O stretching mode increased its relative intensity in the RAIR spectra of PMDA/ODA polyimides, while the bands near 1499 and 1237 cm-1 due to the ODA moieties decreased their relative intensities, implying that PMDA moieties were oriented edge-on with the carbonyl groups perpendicular to the surface and that the ODA moieties were oriented mostly parallel to the surface. However, the RAIR spectra obtained from PMDA and 2,2-bis[4-(4-aminophenoxy)-phenyl]-hexafluoropropane (4-BDAF) polyimides were similar to the transmission spectra of the polyimide, indicating that PMDA/4-BDAF was randomly oriented on the HOPG surface. 相似文献
Five organic precursors, 2,5-dimethyl-2,4-hexadiene, 2,5-norbornadiene, α-terpinine, limonene, and styrene have been studied
as precursors for plasma deposition of low-k films. The films have been produced under particle-forming conditions in the plasma. Accordingly, films have a granular structure
with grain sizes in the range 40–400 nm, as determined by AFM. Annealing at 400 °C preserves the granular structure of the
films while the grain size decreases. Of the five precursors examined, 2,5-dimethyl-2,4-hexadiene and 2,5-norbornadiene produce
films with the lowest dielectric constant, with a value of 3.3. While the dielectric constant varies with deposition conditions
(pressure, flow rate, concentration of precursor), we find that the grain size of the films correlates most closely with the
dielectric constant and conclude that the lowest value of the dielectric constant are obtained under conditions that promote
the formation of particles larger than about 200 nm. 相似文献
We investigated the effect of surface property of polyimide substrate on the formation of pentacene thin-film by using atomic force microscopy (AFM) and X-ray reflectivity (XRR) and diffuse scattering (XDS). Two types of polymer films were prepared: (1) polyimide (PAA-PI) from poly(amic acid) (PAA) (2) polyimide hybrid (PAA-PI-H) prepared by hybridizing the PAA and soluble polyimide (PI) with a octadecyl side chain. The hybridization ratio of PI to PAA was 2/98 in wt%. The water contact angle for PAA-PI-H and PAA-PI were around 80° and 64°, respectively. Morphology of pentacene with a ropelike structure and (1 1 0) peak around 1.4 Å in qz was found when it was deposited on PAA-PI thin-film. Different pentacene morphology was observed when it was deposited on PAA-PI-H thin-film. The different morphology might be due to a 5-6 nm thick additional layer (∼0.95 ρfilm) at the interface between pentacene and PAA-PI-H thin-film caused by a long alkyl side chain introduced to the polymer main chain. 相似文献
We have investigated the bonding of the monomers pyromellitic dianhydride (PMDA) and oxydianiline (ODA) as well as model compounds, succinic anhydride, phthalic anhydride, and benzoic acid, on Cu(111) in ultrahigh vacuum. Unenhanced surface Raman spectroscopy was used to identify the adsorbed species. ODA was unreactive at 110 K; the surface vibrational features were identical to those in the condensed multilayer. In contrast, PMDA chemisorbed dissociatively to form a bidentate surface carboxylate. Succinic anhydride physisorbed at 110 K, whereas benzoic acid and phthalic anhydride both adsorbed dissociatively forming bridging surface carboxylates as was observed for PMDA. The surface Raman spectrum of PMDA showed resonance enhancement. 相似文献
The results of investigations of porous glasses (PG) and porous glasses–ammonium hydrogen sulfate ferroelectric nanocomposites (AHS–PG) are presented. On the basis of dielectric and calorimetric measurements it was shown that in the AHS–PG nanocomposites with average pore size of 44, 68, 95, and 320 nm the anomalies of dielectric permittivity and specific heat similar to those in bulk crystals AHS are observed. An influence of the mean value of pores sizes on the ferroelectric phase transition temperatures of AHS nanocrystals embedded into the porous matrices was determined. It was shown that in AHS–PG dispersion of the dielectric permittivity is observed in both para- and ferro-electric phases and above room temperature AHS–PG nanocomposites exhibit the ionic conductivity. 相似文献
3,3′-diamino-4,4′-dihydroxybiphenyl (DADHBP) was synthesized and its chemical structure was confirmed by Fourier transform infrared (FT-IR) spectroscopy, 1H-nuclear magnetic resonance (1H-NMR), and differential scanning calorimetry (DSC). Then six poly(amic acid) (PAA) solutions were prepared by copolymerization of DADHBP, oxydiphthalicanhydride (ODPA), and 2,2-bis [4-(4-aminophenoxy)phenyl] propane (BAPOPP) in N,N-dimethylacetamide (DMAC) in different mole ratios. The polyimide (PI) films were obtained through thermal imidazation reactions of the thin layers of the above-mentioned precursor solutions. Chemical structures of all PI films were demonstrated by FT-IR. Thermal stabilities and decomposition behaviors of the PI films were tested by DSC and thermogravimetric analysis (TGA). Thermal measurements indicate that the polymers have high thermal stability and produce high char yields. The properties of the PI films were further studied by ultraviolet–visible spectroscopy, water absorption, surface energy, and mechanical measurements. Thermal analysis showed glass transition temperatures between 205.9°C and 276.7°C. Decomposition temperatures were higher than 360.2°C, with 10% weight losses in the range of 448.6°C~517.8°C. The prepared PI films also exhibited good UV absorption, low water absorption (<2%), low surface energy (<44.28 mJ/m2), and good mechanical properties. 相似文献
Polymer blended films of polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):lithium perchlorate (LiClO4) embedded with silver (Ag) nanofiller in different concentrations have been synthesized by a solution casting method. The semi-crystalline nature of these polymer films has been confirmed from their X-ray diffraction (XRD) profiles. Fourier transform infrared spectroscopy (FTIR) and Raman analysis confirmed the complex formation of the polymer with dopant ions. Dispersed Ag nanofiller size evaluation study has been done using transmission electron microscopy (TEM) analysis. It was observed that the conductivity increases when increasing the Ag nanofiller concentration. On the addition of Ag nanofiller to the polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li+ electrolyte system, it was found to result in the enhancement of ionic conductivity. The maximum ionic conductivity has been set up to be 1.14?×?10?5 S cm?1 at the optimized concentration of 4 wt% Ag nanofiller-embedded (45 wt%) polyethylene oxide (PEO)?+?(45 wt%) polyvinyl pyrrolidone (PVP):(10 wt%) Li+ polymer electrolyte nanocomposite at room temperature. Polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li+ +Ag nanofiller (4 wt%) cell exhibited better performance in terms of cell parameters. This is ascribed to the presence of flexible matrix and high ionic conductivity. The applicability of the present 4 wt% Ag nanofiller-dispersed polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li+ polymer electrolyte system could be suggested as a potential candidate for solid-state battery applications. Dielectric constants and dielectric loss behaviours have been studied. 相似文献