Surface modification of polyimide by combining swelling and TiO2 photocatalytic treatments for adhesion improvement of electroless Cu

In order to enhance the adhesion strength between the PI film and the electroless copper film, a combination of swelling and TiO₂ photocatalytic treatments was used to modify polyimide (PI) film. The effects of the swelling solution composition and TiO₂ photocatalytic condition on the surface performance were investigated. After the optimal swelling and photocatalytic treatment, the surface contact angle of the PI film decreased from 85 to 28.7°, and the surface average roughness of the PI film only increased from 1.3 to 13.6?nm, indicating no obvious change for the surface topography of PI film after the photocatalytic treatment. However, the adhesion strength between electroless copper film and the PI film reached to 0.6?KN·m^?1. The FT-IR spectra and XPS analyses indicated that –COOH group was formed on the PI surface after the treatment, and the surface hydrophilicity was improved, which improved the adhesion strength between the PI film and the electroless copper film.     

Effect of Ion Beam Irradiation on Two Nanofiltration Water Treatment Membranes

Abstract

Ion beam irradiation has long been recognized as an effective method for the synthesis and modification of diverse materials, including polymers. Ion beam irradiation is the bombardment of a substance with energetic ions. When the ions penetrate through the surface of a membrane, they may eliminate tall peaks and deep valleys, resulting in an overall reduction in surface roughness. Two nanofiltration membranes, one with a sulfonated polysulfone selective layer and the other with an aromatic polyamide selective layer, were used to study the effects of ion beam irradiation on surface morphology, microstructure, and performance. A beam of 25 keV H⁺ ions with four irradiation fluences (1 × 10¹³ ions/cm², 5 × 10¹³ ions/cm², 1 × 10¹⁴ ions/cm² and 5 × 10¹⁴ ions/cm²) was used for ion beam irradiation of the membrane. Atomic face microscopy (AFM) analysis show that the roughness of the membranes decreased after irradiation. An increase in flux after ion beam irradiation was also observed. Hydrophobicity, pore size distribution, and selectivity of the membrane were not affected by ion beam irradiation.     

Fabrication of fluorine-terminated diamond-like carbon thin film using a hyperthermal atomic fluorine beam

Surface modification of diamond-like carbon (DLC) film was performed using a hyperthermal atomic fluorine beam on the purpose of production of hydrophobic surface by maintaining the high hardness of DLC film. By the irradiation of atomic fluorine beam of a 1.0 × 10²⁰ atoms/cm², the contact angle of a water drop against the DLC surface increased from 73° to 111°. The formation of CF₃, CF₂ and CF bonding on the modified DLC surface was confirmed from the measurements of X-ray photoelectron spectra and near-edge X-ray absorption fine structure spectra. Irradiation of hyperthermal atomic fluorine beam was concluded to produce insulator fluorine-terminated DLC film, which has high F content on the surface, by the taking of the use of neutral atomic beam as a fluorine source.     

Surface modification of polytetrafluoroethylene by Ar+ irradiation for improved adhesion to other materials

A surface of thin square polytetrafluoroethylene (PTFE) samples (1 × 1 × 0.2 cm³) was irradiated with Ar⁺ at 1 keV with varying ion dose from 5 × 10¹⁴ to 1 × 10¹⁷ ions/cm² with and without an oxygen environment. The irradiated surface of the samples was examined by scanning electron microscopy (SEM) for surface textural changes and x-ray photoelectron spectrometry (XPS) for changes in chemical structure. A wettability test was conducted on the irradiated surface of PTFE samples by water droplets. A Scotch ™ tape adhesion test, after a thin film of Cu or Al was evaporated on the irradiated surface, and a tensile test after irradiated samples were glued to sample holders by an adhesive glue (Crystal Bond) was also run. The SEM micrographs showed increasing roughness with fiber forest-like texture with increasing ion dose. The Ar⁺ with an O₂ environment produced finer and denser fiber forest-like texture than that without O₂. The high-resolution XPS spectra showed decreased intensity of the F1s peak and formation of the O1s peak when irradiated with the O₂ environment. The increase of the O1s peak may be attributed to the reaction of oxygen atoms and the free radicals created by Ar⁺ bombardment. The wettability of water droplets on the irradiated surfaces was found to be inversely proportional to the surface roughness. Adhesion tests were conducted on 2000 Å thick Al or Cu film. Full detachment of the metal films was observed when PTFE samples were not modified. Partial detachment of the Al film occurred when PTFE was irradiated without the O₂ environment, regardless of ion dose. No detachment of the film occurred when PTFE was irradiated with the O₂ environment with the ion dose exceeding 1 × 10¹⁶ ions/cm². Partial detachment of Cu film was observed with or without the O₂ environment when the ion dose was 5 × 10¹⁴ ions/cm². No detachment occurred with or without the O₂ environment when the ion dose was 1 × 10¹⁵ ions/cm² or greater. The tensile test showed that adhesion of an adhesive cement (Crystal Bond) to the irradiated PTFE samples increased significantly with increasing ion dose up to 1 × 10¹⁶ ions/cm². Possible mechanisms for the improved adhesion are given. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1913–1921, 1997     

Enhancing adhesion by ion beam-induced atomic mixing at the interface between copper film and polyimide substrate

Ion beam mixing was used to improve the adhesion between deposited Cu film (400 Å) and polyimide (PI) substrate. Ar⁺ ion with the energy levels between 180 and 200 keV, and the dose between 10¹⁴ to 4 × 10¹⁶ ions/cm² were used. The surface analyses were carried out by Rutherford Backscattering Spectroscopy (SEM). RBS analysis, using 2 MeV He⁺ ions, showed mixing of Cu and FI and the mixing depended on the Ar⁺ energy and dose. The X-ray study showed a very broad halo for deposited Cu film but the (111) peak appeared after the Ar⁺ implantation and the peak increased with Ar⁺ ion dose. Optical micrographs showed that Cu film formed circular bubbles after many thermal cycles when adhesion was poor and fracture cracks when adhesion was good.     

Surface characterization of polymers modified by keV and MeV ion beams

The present work deals with two different surface modification techniques for altering the surface properties of polymers: plasma treatment and ion implantation. Polymer foils were exposed in an inductively-coupled r.f. (13.56 MHz) plasma system with and without applying a negative high voltage pulse to the sample stage. The influence of low pressure plasmas of oxygen, nitrogen, or argon on the chemical composition, topography, and wettability of polymer surfaces was studied in detail. Etch rates of poly(ethylene terephthalate) for different plasma parameters were monitored. The polymer surface was also modified by a high energy ion beam process. Polyimide films were implanted with different ion species such as Ar⁺, N⁺, C⁺, He⁺, and O⁺ at doses from 1 × 10¹⁵ to 1 × 10¹⁷ ion/cm². Ion energy was varied from 10 to 60 keV for the plasma source ion implantation (PSII) experiment. Polyimide samples were also implanted with 1 MeV hydrogen, carbon, and oxygen ions at a dose of 1 × 10¹⁴ ion/cm². Depending on the ion energy, dose, and ion species, the surface resistivity of the film was reduced by several orders of magnitude. A study on the plasma-treated and ion beam-treated polymer surfaces was performed using TOF-SIMS, XPS, SEM, AFM, and water contact angle measurements.     

Plasma surface modification of polyimide for improving adhesion to electroless copper coatings

The influences of oxygen plasma treatment of polyimide (PI) films on the adhesion of electroless copper coatings as well as on the chemical composition of the film surface and the PI surface morphology were investigated. The plasma operating parameters were 1800 W forward power with O₂ flowing at a rate of 300 cm³/min at a pressure of 200 mTorr. The peel strength increased with decreasing plasma treatment temperature. However, extension of the treatment time at higher temperatures had a positive effect on adhesion. A correlation between the enhancement in peel strength and the content of oxygen-containing groups at the PI surface (investigated using XPS) was observed. A change in the morphology as a result of plasma etching was also observed, in the formation of pits in the film surface. The pits ranged from 3 to 6 μm in depth and the diameter varied from 10 to 200 μm. Comparison of the data obtained after plasma treatment with the results of chemical etching in alkaline solutions of permanganate showed approximately the same adhesion increase (to 0.6 kN/m) in both cases. However, chemical etching did not affect the surface morphology and increased the oxygen content at the PI surface less than the plasma treatment.     

Surface reaction on polyvinylidenefluoride (PVDF) irradiated by low energy ion beam in reactive gas environment

Polyvinylidenefluoride (PVDF) was irradiated by a keV Ar⁺ ion in O₂ environment for improving adhesion between PVDF and Pt, and reaction between PVDF and the ion beam has been investigated by X‐ray photoelectron spectroscopy (XPS). The adhesion test between Pt and the modified PVDF was carried out by boiling test, in which the specimens were kept in boiling water for 4 h. Two failure modes (buckling up due to weak adhesion and crack formation due to strong adhesion) of Pt films have been observed in the system. Contact angle of PVDF was reduced to 31 from 75° by the irradiation of 1 × 10¹⁵ Ar⁺ ions/cm² with oxygen flow rate of 8 sccm. The surface of the irradiated PVDF became more rough as ion dose increased. The improved adhesion mechanism and identification of newly formed chemical species have been confirmed by Carbon 1s and Fluorine 1s X‐ray photoelectron core‐level spectra. The main reaction occurred at the irradiated PVDF surface is an ion‐beam‐induced oxidation accompanied with preferential sputtering of fluorine. Newly formed chemical species at interface are regarded as ester and carboxyl groups. Adhesion of the Pt–PVDF interface was improved by ion irradiation in O₂ environment. This improvement is originated from the presence of carbon—oxygen bonds on the irradiated PVDF surface. Comparison of failure modes on the irradiated PVDF at various conditions after the boiling test shows that adhesion of Pt film is largely affected by the product of ion‐assisted reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 41–47, 1999     

Comparative study of gamma and ion beam irradiation of polymeric nanocomposite on electrical conductivity

Poly(vinyl alcohol) (PVA) was used to prepare nanocomposites of multi‐wall carbon nanotubes (MWCNT) and functionalized carbon nanotubes (MWCNT‐NH₂) in existence of 2‐carboxyethyl acrylate oligomers (CEA). Radiation‐induced crosslinking of the prepared matrix was carried out via gamma and ion beam irradiation. A comparative study of gamma and ion beam irradiation effect on the electrical conductivity of nanocomposite was conducted. The gelation of the gamma irradiated matrix outperforms the ion beam irradiated matrix. The order of gelation is PVA > (PVA/CEA) > (PVA/CEA)‐MWCNT > (PVA/CEA)‐MWCNT‐NH₂. There is a significant reduction in the swelling of the nanocomposite. The formation of nanocomposites was confirmed by scanning electron microscopy, energy‐dispersive X‐ray (EDX) and FTIR examinations. The direct current electrical properties of PVA/nanocomposites are examined at room temperature by applying electric voltage from 1 to 20 V. The results revealed that the electrical conductivity is increased by adding the carbon nanotubes and irradiation by gamma and ion beam. At an applied electric voltage 20 V, in the electrical conductivity of the unirradiated PVA was from 9.20 × 10^?8 S cm^?1. After adding MWCNT an increase up to 4.70 × 10^?5 S cm^?1 was observed. While after ion beam irradiation, a further increase up to 9.30 × 10^?5 S cm^?1 was noticed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46146.     

Degradation of polyimide by implantation with Ar+ ions

Polyimide (PI) samples were irradiated with 200 keV Ar⁺ ions to fluences from 5 × 10¹³−1 × 10¹⁷ cm⁻² and the concentration depth profiles of implanted Ar atoms as well as of carbon and oxygen atoms of the polymer matrix were determined using the Rutherford backscattering technique. The surface polarity, sheet resistivity, and thermoelectric power of PI samples were also determined as a function of the ion fluence and temperature. As a result of the ion irradiation, the polyimide surface layer is depleted of oxygen and enriched by carbon. The sheet resistivity exhibits a minimum at the ion fluence of 5 × 10¹⁶ cm⁻² and the temperature dependence of the sheet resistivity indicates the semiconducting character of irradiated PI and the variable range hopping mechanism of charge transport. The thermoelectric power of the PI samples irradiated to high fluences is small, of the order of μV/K, and independent of temperature. This behavior is typical for metals. The simultaneous appearance of metal and semiconducting properties is probably due to the complex structure of the PI surface layer modified by the ion irradiation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 723–728, 1997     

Surface modification of low‐density polyethylene (LDPE) film and improvement of adhesion between evaporated copper metal film and LDPE

To improve the interfacial adhesion between evaporated copper film and low‐density polyethylene (LDPE) film, the surface of LDPE films was modified by treating with chromic acid [K₂Cr₂O₇/H₂O/H₂SO₄ (4.4/7.1/88.5)]/oxygen plasma. Chromic‐acid‐etched LDPE was exposed to oxygen plasma to achieve a higher content of polar groups on the LDPE surface. We investigated the effect of the treatment time of chromic acid in the range of 1–60 min at 70°C and oxygen plasma in the range of 30–90 sec on the extent of polar groups created on the LDPE. We also investigated the surface topography of and water contact angle on the LDPE film surface, mechanical properties of the LDPE film, and adhesion strength of the evaporated copper metal film to the LDPE film surface. IR and electron spectroscopy for chemical analysis revealed the introduction of polar groups on the modified LDPE film surface, which exhibited an improved contact angle and copper/LDPE adhesion. The number of polar groups and the surface roughness increased with increasing treatment time of chromic acid/plasma. Water contact angle significantly decreased with increasing treatment time of chromic acid/plasma. Combination treatment of oxygen plasma with chromic acid drastically decreased the contact angle. When the treatment times of chromic acid and oxygen plasma were greater than 10 min and 30 sec, respectively, the contact angle was below 20°. With an increasing treatment time of chromic acid, the tensile strength of the LDPE film decreased, and the film color changed after about 10 min and then became blackened after 30 min. With the scratch test, the adhesion between copper and LDPE was found to increase with an increasing treatment time of chromic acid/oxygen plasma. From these results, we found that the optimum treatment times with chromic acid and oxygen plasma were near 30 min and 30 sec, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1677–1690, 2001     

Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system

Nano-titania (TiO₂) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO₂ hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N₂ and Ar/O₂) were also applied in this study to improve the adhesion strength. The Ar/N₂ plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO₂-1 wt% hybrid film with Ar/N₂ plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O₂ plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO₂ hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO₂ on the adhesion strength between PI/TiO₂ hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO₂ hybrid film and copper was proposed in this study.     

The effect of TiO2 morphology on the surface modification of poly (ethylene terephthalate) for electroless plating

In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO₂ photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO₂ crystal forms, TiO₂ particle sizes, and TiO₂ content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO₂ with a particle size of 5 nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4° to 19.8°, and the surface roughness of the PET film increased from 36 to 117 nm. The adhesion strength between the PET film and the electroless copper film reached 0.89?KN?m^?1. X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO₂ photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.     

Effect of Au ion beam on structural,surface, optical and electrical properties of ZnO thin films prepared by RF sputtering

In the present work, ZnO thin films were irradiated with 700?keV Au⁺ ions at different fluence (1?× 10¹³, 1?× 10¹⁴, 2?× 10¹⁴ and 5?× 10¹⁴ ions/cm²). The structural, morphological, optical and electrical properties of pristine and irradiated ZnO thin films were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM), spectroscopy ellipsometry (SE) and four point probe technique respectively. XRD results showed that the crystallite size decreased from pristine value at the fluence 1?×?10¹³ ions/cm², with further increase of ion fluence the crystallite size also increased due to which the crystallinity of thin films improved. SEM micrographs showed acicular structures appeared on the ZnO thin film surface at high fluence of 5?×?10¹⁴ ions/cm². FTIR showed absorption band splitting due to the growth of ZnO nanostructures. The optical study revealed that the optical band gap of ZnO thin films changed from 3.08?eV (pristine) to 2.94?eV at the high fluence (5?× 10¹⁴ ions/cm²). The electrical resistivity of ZnO thin film decreases with increasing ion fluence. All the results can be attributed to localized heating effect by ions irradiation of thin films and well correlated with each other.     

The effect of Ne+ ion implantation on polyimide film

The fluence of Ne⁺ ion irradiation on the surface modification of polyimide (Kapton HN type) film was investigated. The irradiation of ion implantation onto a polyimide film was performed, and the surface chemical structure was analyzed in detail by X-ray photoelectron spectroscopy (XPS). An acceleration voltage of 100 keV was used in the ion implantation with different doses from 5 × 10¹⁴ to 5 × 10¹⁷ ion cm^?2 and a beam current density of 10 μA cm^?2. The elemental ratios of carbon, oxygen and nitrogen were calculated from 1s peaks of the corresponding elements. The results showed that the content of carbon in the surface layer increased after ion irradiation, while the ratios of oxygen decreased after irradiation, especially in the case of the polyimide film treated at ion fluence. The O1s spectra after ion irradiation are related to the rearrangement of those recoil atoms and the ion incorporated into the film and the formation of new types of bond, such as C–O and O–O.     

Low-energy He-ion beam modifications the surface properties of biomaterial

In the present work, ultra-high-molecular-weight polyethylene (UHMWPE) films were irradiated with 130 keV He ions. The fluence of the ion beam was ranged from 1 × 10¹² to 1 × 10¹⁶ cm^?2. The chemical, morphological, and crystallite structure changes resulted from the ion bombardment were obtained using different spectroscopic techniques. These techniques were Fourier transform infrared spectrometer, scanning electron microscope, X-ray diffraction, and UV–vis spectrophotometry. The surface free energy for untreated and ion-beam-treated samples was determined by means of contact angle measurements of three different liquids. Our results showed a decrease in the crystallinity of UHMWPE and formation of C=O groups on the polymer surface for modified samples as well. A remarkable shifting in the UV–vis spectra toward lower energy and increase in the optical absorption were observed as the ion fluence increases. Measurements of the contact angle indicate remarkable increase in the surface free energy as a function of ion fluence.     

Atomic order-disorder engineering in the La2Zr2O7 pyrochlore under low energy ion irradiation

Cation and anion disordering affect the structural and electronic properties of the isometric A₂B₂O₇ pyrochlore materials. Here, we report a study on the structural response of La₂Zr₂O₇ at two different temperatures (300 K and ~88 K) as a function of ion fluence (1 × 10¹³, 5 × 10¹³, and 1 × 10¹⁴ ions/cm²). The effect of ion fluence and irradiation temperature on the structural properties have been investigated using the grazing angle x-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. GIXRD results confirmed that the weakening/broadening of the diffraction peaks and lattice volume expansion increases monotonically as a function of ion fluence at both the temperatures and are more pronounced at ~88 K. The cation and anion disordering appear to be ion fluence and irradiation temperature-dependent. Raman spectroscopy shows that the atomic disordering is more pronounced with enhanced ion fluence and revealed the involvement of the X_48f parameter in the enhancement of disordering in the system. The HRTEM analysis revealed that the deterioration in the atomic ordering (amorphization) is significantly more pronounced at ~88 K. The qualitative analysis of cation/anion disordering and structural deformation revealed that irradiation parameters play a crucial role in developing and altering the properties of the pyrochlore materials for the technological applications.     

Role of structural modification on the electrical properties of poly(ethylene terephthalate) irradiated with 90‐MeV carbon ion beam

Thin films of poly(ethylene terephthalate) (PET) having a thickness of 100 μm were exposed to different ion fluence of swift heavy ions of carbon in the range of 5 × 10¹¹ – 5 × 10¹³ ions/cm². The effect of ion beam on structural and electrical modification has been studied by UV/vis, FTIR, X‐ray diffraction (XRD), Differential Scanning Calorimetery (DSC), and AC electrical measurement techniques. On irradiation, a shift in absorption wavelength toward the red end of spectrum with increase of ion fluence was observed. The intensity of crystalline IR bands and main diffraction peak in XRD pattern were found to decrease with increase in ion fluence. It indicates the loss of crystallinity induced by ion‐beam irradiation. The crystallite size was found to increase on irradiation. The melting temperature (T_m) of PET films increased at a low ion dose (5.0 × 10¹² ions/cm²), while it decreased at higher ion fluence (50.0 × 10¹² ions/cm²). The dielectric constant (ε′) of PET films was increased with increase of ion fluence. The modifications brought about in the dielectric constant are correlated with chemical and molecular structural changes occurring on irradiation. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Ion beam ablation of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was irradiated with 300 keV Ar⁺ ions to the fluences of 1 × 10¹⁴ to 1 × 10¹⁶ cm⁻²; the PTFE structural changes induced by the ion irradiation were studied by X-ray diffraction and UV–vis and IR spectroscopies. The electrical conductivity of the ion beam modified PTFE was also investigated using the standard technique, and the alterations of the surface polarity were determined by contact angle measurements. The ion irradiation leads to intensive PTFE ablation due to the breaking of the C—C bonds in the polymer molecular chains and due to the production and liberation of the molecular fragments C_xF_y. In contrast to other polymeric materials, the irradiated PTFE carbonizes to a lesser extent and the observed irradiation induced increase of the electrical conductivity is also not significant. In-coming ions cause a reduction of the crystalline phase content in the PTFE samples. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 69: 1257–1261, 1998     

Structure and dielectric properties of polyimide/silica nanocomposite nanofoam prepared by solid‐state foaming

In this article, polyimide (PI)/silica nanocomposite nanofoams were prepared by solid‐state foaming using supercritical CO₂ as foaming agent. To control the cell size and morphology of the PI/silica foam, the silica nanoparticles as nucleating agent were in situ formation from TEOS via sol‐gel process, which make the silica nanoparticles homogeneously dispersed in PI matrix. The resulting PI/silica nanocomposite nanofoams were characterized by scanning electron microscopy (SEM), the image analysis system attached to the SEM and dielectric properties measurements. In PI/silica nanocomposite nanofoams, one type of novel morphology was shown that each cell contained one silica nanoparticle and many smaller holes about 20–50 nm uniformly located in the cell wall. This special structure could visually prove that the nucleation sites during foaming were formed on the surface of nucleating agents. Compared with those of neat PI foam, the cell size of PI/silica nanocomposite nanofoams was smaller and its distribution was narrower. The dielectric constant of PI/silica nanocomposite nanofoams was decreased because of the incorporation of the air voids into the PI/silica nanofoams. While the porosity of PI/silica nanocomposite nanofoam film was 0.45, the dielectric constant of the film (at 1 MHz) was reduced from 3.8 to about 2.6. Furthermore, the dielectric constant of PI/silica nanofoam films remained stable across the frequency range of 1×10²～1×10⁷ H_Z. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42355.