Pyroelectric and dielectric properties of spin‐coated thin films of vinylidene fluoride–trifluoroethylene copolymers

This work emphasizes the use of vinylidene fluoride and trifluoroethylene copolymer P(VDF‐TrFE) as a pyroelectric sensor. The pyroelectric and dielectric properties of the copolymer have been investigated in the temperature interval 150–350 K. The samples were prepared by using a spin‐coating technique with 70/30 mol% VDF/TrFE copolymer. The final film thickness of the samples, which is mainly determined by the concentration of the copolymer, spinning rate and spin time, was measured with a surface profiler. The samples were annealed at 150 °C for 10 min to improve the crystallinity of the copolymer. The crystallinity of the annealed and non‐annealed samples was compared by IR spectroscopy. The most effective process by which to improve the pyroelectric response of the material is to pole the sample with huge poling field‐strengths at elevated temperatures. Both pyroelectric and dielectric activities of the samples were measured after each successful poling process. It was observed that while the pyroelectric activity of the material increases, the dielectric activity decreases, so the figure‐of‐merit of the material, which shows the sensor capability of the material, was increased by a significant amount. It was found that the pyroelectric coefficient of VDF/TrFE (70/30 mol%) copolymer is 68.7 µC m^?2 K^?1 at 300 K. © 2001 Society of Chemical Industry     

Preparation and characterization of thin films of the poly(p‐phenylene vinylene) semiconducting polymer

Conjugated polymers have been the subject of many studies because of their widespread applications in electronic and optoelectronic devices. Poly(p‐phenylene vinylene) is a leading semiconducting polymer in optical applications. This work is focused on the development of thin films of poly(p‐phenylene vinylene) by spin coating and their characterization with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy to understand their changes. An empirical model has been developed to show the effect of the variables—the spin speed, polymer concentration, and spin time—on the film thickness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Microstructural,wetting, and dielectric properties of plasma polymerized polypyrrole thin films

Polypyrrole (PPy) thin films were synthesized by plasma polymerization technique and investigated the influence of discharge power on microstructural, optical, surface wettability, and dielectric properties of grown films. As deposited PPy films were characterized by X‐ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), Atomic force microscopy, UV‐VIS spectroscopy and dielectric spectroscopy. The broad XRD peak present at 2θ = 23.5° revealed the amorphous nature of grown PPy films. The FTIR spectra displayed characteristic peaks in the wavenumbers regions 3300–3400 cm^?1 and 1635–1700 cm^?1 and respective peaks intensities decreased slightly as a function of discharge powers. Significant modifications in surface morphology of the films were observed as a function of discharge powers and PPy films synthesized at higher discharge power of 50 W demonstrated characteristic surface morphology composed of characteristic vertical cone shaped clusters provided with rms roughness of 3.42 nm. The UV‐VIS absorption spectra evidenced that the optical density values varied as a function of discharge power. The evaluated band gap energies decreased with an increase of discharge power and found to be 2.53 eV for PPy films prepared at higher discharge power of 50 W. The surface wettability studies evidenced that as prepared PPy films were found to be hydrophilic in nature. The dielectric measurements were carried out for “ITO/polymer/ITO” structures in the frequency range 10 mHz to 100 kHz. As evidenced from dielectric spectroscopic measurements, PPy films synthesized at 50 W were demonstrated conductivity value of 6.0 × 10^?12 S/m. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43982.     

Formation of nanoporous poly(methyl silsesquioxane) thin films using adamantane for low‐k application

Nanoporous poly(methyl silsesquioxane) PMSSQ thin films for low‐k application have been prepared using chemically attached adamantylphenols as pore generating materials (porogen). To obtain the mechanically stable porous structure, multifunctional 1,2‐bistrimethoxysilylethane (BTMSE) was employed in addition to methyltrimethoxysilane as a main matrix material. From the decomposition of porogen, confirmed by FTIR and TGA, the nanoporous thin films containing pores less than 5 nm, which are characterized using sorption analysis, were successfully achieved. The dielectric constant was significantly decreased to 1.9, while maintaining the stable mechanical properties with the elastic modulus of 3.7 GPa measured by a nanoindenter. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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.     

Novel low‐dielectric‐constant copolyimide thin films composed with SiO2 hollow spheres

A series of copolyimide/SiO₂ hollow sphere thin films were prepared successfully based on bis[3,5‐dimethyl‐4‐(4‐aminophenoxy)phenyl]methane and 9,9‐bis(4‐(4‐aminophenoxy)phenyl)fluorene (molar ratio = 3 : 1) as diamine, and 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride) as dianhydride, with different wt % SiO₂ hollow sphere powder with particle size 500 nm. Some films possessed excellent dielectric properties, with ultralow dielectric constants of 1.8 at 1 MHz. The structures and properties of the thin films were measured with Fourier transform infrared spectra, scanning electron microscope, thermogravimetric analysis, and dynamic mechanical thermal analysis. The polyimide (PI) films exhibited glass‐transition temperatures in the range of 209– 273°C and possessed initial thermal decomposition temperature reaching up to 413–477°C in air and 418–472°C in nitrogen. Meanwhile, the composite films were also exhibited good mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

高介电HfO_xN_y薄膜的制备及其光学性能研究

采用直流反应磁控溅射方法,在硅衬底制备了高介电HfOxNy薄膜。用椭偏仪研究了后期退火处理对薄膜光学性质的影响,结果表明,薄膜的折射率随退火温度的升高而增加,这主要是由于高温退火导致薄膜内部缺陷减少,使得薄膜松散的内部结构变得更加致密;薄膜的消光系数随退火温度的升高而降低,这是由于因为退火后薄膜内的缺陷减少。光学禁带宽度随退火温度的升高而增加,这是由于退火过程中薄膜中N含量的减少而导致。     

Preparation and properties of layered silicate/polyimide hybrid films

Layered silicate/polyimide (PI) hybrid films were prepared from 4,4′‐oxydianiline, 3,3′,4,4′‐oxydiphthalic anhydride, and chemically modified montmorillonite via an in situ intercalation polymerization pathway. The X‐ray diffraction and transmission electron microscopy results indicated that the silicates were homogeneously dispersed as exfoliated layers in the PI hybrid film with 2% silicate. The mechanical properties and thermal stabilities of the PI hybrid films changed with the content of the layered silicates. The coefficient of thermal expansion and water uptake of the PI hybrid films decreased with increasing silicate contents because of the barrier effect of platelike silicate layers, which prevented the diffusion and penetration of water. The dielectric strength and electrical aging performance of the PI hybrid films could also be improved as the silicate layer highly dispersed in the films. For the hybrid PI film with 5% layered silicate, the time to failure during electrical aging exceeded 280 h, which was 2.5 times as long as that of pure PI film. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1176–1183, 2005     

Effect of microstructure on the dielectric properties of poly(vinyl alcohol)–poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) composite films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) was blended with poly(vinyl alcohol) (PVA) to form 0, 10, 20, 30, 40, and 50 vol % PEDOT–PSS/PVA solutions, and their freestanding films were prepared with a simple and cost‐effective solution casting technique at 27 °C in the absence of additives. Field emission scanning electron microscopy images revealed changes in the cocontinuous network to a rodlike morphology in the composite films from 10 to 50 vol % PEDOT–PSS/PVA. The alternating‐current conductivity was found to obey Jonscher's power law. The obtained values of the dielectric constant at 27 °C were relatively high, and a maximum value of 6.7 × 10⁴ at 100 Hz for 40 vol % PEDOT–PSS'/PVA was observed. The dielectric loss attained a maximum value of about 10⁶ at 100 Hz for 40 vol % PEDOT–PSS/PVA. However, a decrease in the dielectric parameters was observed at 50 vol % PEDOT–PSS/PVA because of locally induced strain in the microstructure. The variations in polarization with respect to the applied electric field (P–E) were determined for 50, 100, and 500 Hz at 500 V for the freestanding composite films of lower concentrations up to 20 vol % PEDOT–PSS/PVA. In summary, the dielectric and P–E measurements confirmed that the electrical characteristics changed in accordance to the contribution from both resistive and capacitive sites in the PEDOT–PSS/PVA composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45079.     

Hyperbranched-polysiloxane-based hyperbranched polyimide films with low dielectric permittivity and high mechanical and thermal properties

A series of hyperbranched polysiloxane (HBPSi)-based hyperbranched polyimide (HBPI) films with low dielectric permittivity and multiple branched structures are fabricated by copolymerizing 2,4,6-triaminopyrimidine (TAP) with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 4,4′-diaminodiphenyl ether, and HBPSi via the two-step polymerization method. The dielectric permittivity of HBPSi hyperbranched polyimide films decreases with increasing TAP fraction, namely, from 3.28 for sample PI-1 to 2.80 for PI-4, mainly owing to the enlarged free volume created by the incorporation of multiple branched structures. Moreover, HBPSi HBPI possesses desirable solubility and good mechanical properties and thermal stability. PI-4 not only has low dielectric permittivity (2.80, 1 MHz), excellent solubility (soluble in several common organic solvents), and remarkable thermal properties (glass-transition temperature of 273 °C, 5% weight loss temperature of 498 °C in N₂ and 486 °C in O₂), but it also demonstrates admirable mechanical properties with a tensile strength of 103 MPa, elongation at break of 7.3%, and a tensile modulus of 2.16 GPa. HBPSi HBPI might have potential applications in interlayer dielectrics and other microelectronics fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47771.     

Phosphorus‐containing polyhedral oligomeric silsesquioxane/polyimides hybrid materials with low dielectric constant and low coefficients of thermal expansion

Novel phosphorus‐containing polyhedral oligomeric silsesquioxane (POSS)/polyimides (PI) hybrid materials with low dielectric constant and low linear coefficients of thermal expansion (CTE) were prepared and characterized. The POSS/PI hybrid materials were synthesized with octa(aminopropyl)silsesquioxane (OAPS) and a series of phosphorus‐containing polyamide acids(PAA). The PAAs were synthesized with bis(4‐aminophenoxy) phenyl phosphine oxide (BAPPO), 4,4’‐diaminodiphenyl ether (ODA) and 3,3',4,4'‐biphenyl tetracarboxylic diandhydride (BPDA). The structures and properties of the hybrid materials were characterized. And the effect of the phosphorus‐containing structure on the POSS/PI hybrid materials was discussed. The dielectric constants and CTE of the hybrid materials were remarkably lower than that of the unmodified POSS/PI films. The lowest values of dielectric constant and CTE could achieve as low as 2.64 (1 MHz) and 27.45 ppm/K. Besides, the hybrid materials also had excellent thermal properties. The highest 5% weight loss temperature of the hybrid materials was as high as 580°C under air. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42611.     

Design and preparation of poly(aryl ether ketone)/phosphotungstic acid hybrid films with low dielectric constant

A material with low dielectric constant was produced using nanoparticle phosphotungstic acid (PWA) modified by the silane coupling agent γ‐aminopropyltriethoxysilane (KH‐550) dispersed in a poly(aryl ether ketone) containing (3‐trifluoromethyl) phenyl side groups (FPEEK) matrix synthesized with (3‐trifluoromethyl) phenyl hydroquinone (3FHQ) and 4,4′‐difluorobenzophenone. The material was fabricated using solution‐blending. Moreover, the dielectric, thermal, and mechanical properties of this material were characterized using a precision impedance analyzer, thermal gravimetric analyzer, and universal tester, respectively. The results indicate that modified PWA (m‐PWA)/FPEEK composites show obvious improvement in the dielectric properties compared to unmodified PWA (p‐PWA)/FPEEK composites. This should be attributed to the good dispersion and compatibility of m‐PWA in FPEEK, as proven by scanning electron microscope and wide‐angle X‐ray diffraction. Besides, m‐PWA/FPEEK composites also exhibited the relatively good thermal and mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Multifunctional epoxy resin/polyacrylonitrile‐lithium trifluoromethanesulfonate composites films with very high transparency,high dielectric permittivity,breakdown strength and mechanical properties

Multifunctional transparent composite films with high dielectric permittivity (high‐k), breakdown strength, and mechanical properties are urgently required by cutting‐edge fields. Herein, novel multifunctional films were facilely prepared through building unique cross‐linked structure based on epoxy resin (EP) and polyacrylonitrile (PAN)‐lithium trifluoromethane sulfonate (LiTf) complex. Compared with high‐k materials reported previously, EP/(PAN‐LiTf) films simultaneously show very high transparency, good flexibility, high tensile, and breakdown strengths. For 0.22EP/(PAN‐LiTf) film with 22 wt % EP, its average transmittance and elongation at break are as high as 91% (600–800 nm) and 12.7%, respectively; moreover, its dielectric permittivity, AC breakdown strength and the maximum energy density are severally about 4.9, 1.8, and 15.2 times of those of EP resin, completely overcoming the sticky problems in conductor/polymer composites. The origin behind these attractive properties is intensively discussed, and believed to be attributed to the unique structure of EP/(PAN‐LiTf) films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45218.     

Preparation and properties of cardanol‐based polybenzoxazine/SiO2 hybrids by sol‐gel technique

A new cardanol‐based benzoxazine monomer containing a hydroxyl group (CBZ) was synthesized and characterized by FT‐IR and ¹H NMR spectroscopy. The formation mechanism of cardanol‐based polybenzoxazine/SiO₂ hybrids from CBZ and tetraethoxysilane (TEOS) by sol‐gel technique was invested by FT‐IR analysis. FT‐IR and SEM confirmed that there were many SiO₂ particles formed and embedded in the cardanol‐based polybenzoxazine. A phase separation occurred when the ratio (wt) of TEOS to CBZ was not less than 3 : 5. TGA results illuminated the thermal stability and char yield of cardanol‐based polybenzoxazine could be enhanced due to the formation of SiO₂ particles in the polybenzoxazine matrix. Incorporation of SiO₂ could improve the surface de‐wetting and anti‐ultraviolet properties of the films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

GO@TA-Fe/PVDF纳米复合材料制备与介电性能

为降低氧化石墨烯（GO）/聚偏氟乙烯（PVDF）体系的介电损耗,本文采用单宁酸-铁配合物（TA-Fe）修饰GO表面,将改性GO和PVDF复合后制得了GO@TA-Fe/PVDF纳米复合电介质材料,研究了GO@TA-Fe对PVDF复合材料的微观形貌及介电性能影响。研究结果表明,TA-Fe包覆层强化了GO与PVDF基体间界面相容性及界面作用力,促进了GO在基体中均匀分散;TA-Fe界面层的存在显著降低了GO/PVDF漏导电流及损耗,归因于绝缘界面层有效阻止了GO之间直接接触,抑制漏导电流;TA-Fe用量对体系介电性能有明显影响,随TA-Fe用量增大,体系的介电损耗和电导率显著降低。与GO/PVDF相比,质量分数2%的GO@TA-Fe/PVDF在100Hz下介电常数为1000,而介电损耗由19.8降低为0.08。本研究制备的高介电常数及低损耗的柔性GO@TA-Fe/PVDF纳米电介质材料在电子器件及电力设备领域具有潜在应用。     

Surface,interface and electronic properties of F8:F8BT polymeric thin films used for organic light‐emitting diode applications

Ultrathin polymeric films consisting of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (F8) blended with poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT) grown onto PEDOT:PSS/ITO/PET were investigated by X‐ray photoelectron spectroscopy (XPS), depth‐profiling XPS, reflection electron energy loss spectroscopy (REELS) and angle‐dependent X‐ray absorption spectroscopy (XAS) to gain information on the films' electronic, order and interface properties. AFM studies provide valuable information on the films' nanotopographical properties and homogeneity. Spectroscopic ellipsometry and photoluminescence spectroscopy were used also to obtain information on the optoelectronic properties. Well‐ordered films were observed from the XAS analysis, measured at the sulfur K absorption edge. XPS measurements demonstrated that the surface composition of the polymer thin films prepared by a spin‐coating wet‐chemical deposition method matches the expected F8:F8BT blend stoichiometry. The interfacial properties were studied through an argon ion sputtering process coupled to the XPS acquisition, showing an enhancement of oxygen components at the interface. The films' inhomogeneity was verified by AFM images and analysis. We obtained a value of 3.1 eV as the electronic bandgap of the F8:F8BT film from REELS data, whereas analysis of the spectroscopic ellipsometry spectra revealed that the optical bandgap of F8:F8BT has a value of 2.4 eV. A strong green emission was obtained for the produced films, which is in agreement with the expected emission due to the 1:19 ratio of the F8 and F8BT blended polymers. © 2018 Society of Chemical Industry     

Synthesis and characterization of novel adamantane‐based copoly(aryl ether ketone)s with low dielectric constants

A series of novel adamantane‐based copoly(aryl ether ketone)s (PAEK‐CF₃‐Ad) with low dielectric constants were prepared by post‐amidation of copoly(aryl ether ketone)s containing (3‐trifluoromethyl)phenyl and carboxyl groups with 4‐adamantylaniline. Compared with the preparation of adamantane‐containing poly(aryl ether ketone)s by direct polymerization of adamantyl‐substituted monomers, this side‐chain grafting method avoids various problems, such as high polymerization temperature and the difficult polymerization of adamantyl‐substituted monomers. The dielectric, thermal and mechanical properties of the synthesized PAEK‐CF₃‐Ad were characterized using a precision impedance analyzer, differential scanning calorimetry and thermogravimetric analysis, and a universal tester, respectively. The results indicate that PAEK‐CF₃‐Ad films exhibited low dielectric constants ranging from 2.33 to 2.65 at 1 MHz due to the introduction of the adamantyl groups. The synthesized PAEK‐CF₃‐Ad copolymers exhibited good thermal and mechanical properties. © 2013 Society of Chemical Industry     

Microwave dielectric and nonlinear optical studies on radio‐frequency sputtered Dy2O3‐doped KNN thin films

We report the effect of oxygen mixing percentage (OMP) on structural, microstructural, dielectric, linear, and nonlinear optical properties of Dy₂O₃‐doped (K_0.5Na_0.5)NbO₃ thin films. The (K_0.5Na_0.5)NbO₃ + 0.5 wt%Dy₂O₃ (KNN05D) ferroelectric thin films were deposited on to quartz and Pt/Ti/SiO₂/Si substrates by RF magnetron sputtering. An increase in the refractive index from 2.08 to 2.21 and a decrease in the optical bandgap from 4.30 to 4.28 eV indicate the improvement in crystallinity, which is also confirmed from Raman studies. A high relative permittivity (ε_r=281‐332) and low loss tangent (tanδ=1.2%‐1.9%) were obtained for the films deposited in 100% OMP, measured at microwave frequencies (5‐15 GHz). The leakage current of the films found to be as low as 9.90×10^?9 A/cm² at 150 kV/cm and Poole‐Frenkel emission is the dominant conduction mechanism in the films. The third order nonlinear optical properties of the KNN05D films were investigated using modified single beam z‐scan method. The third order nonlinear susceptibility (?χ⁽³⁾?) values of KNN05D films increased from 0.69×10^?3 esu to 1.40×10^?3 esu with an increase in OMP. The larger and positive nonlinear refractive index n₂=7.04×10^?6 cm²/W, and nonlinear absorption coefficient β=1.70 cm/W were obtained for the 100% OMP film, indicating that KNN05D films are good candidates for the applications in nonlinear photonics and high‐frequency devices.     

POSS‐based molecular hybrids with low dielectric constant: Effect of chemical structure and molecular architecture

Three kinds of hybrids with different architectures including dumbbell‐type, bead‐type, and cross‐linked structure, were prepared via the Heck reaction between octavinyl‐polyhedral oligomeric silsesquioxane (OV‐POSS) and different bromo‐substituted aromatic amide monomers. The molecular architecture can be successfully achieved by simply varying the feed ratio of OV‐POSS to monomers. Their structure and properties were characterized by FTIR, ¹H NMR, ²⁹Si NMR, provide the expansion for FTIR and NMR] All the POSS‐based hybrids exhibited good thermal stability and low dielectric constant properties. The relationship between chemical structure, molecular architecture, and the dielectric constant of these hybrids were investigated in detail. The results show that POSS content dominated the low dielectric constant of the hybrids, while the chemical structure of organic chains and molecular architecture also play an important role on the formation of low dielectric constant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42292.     

Synthesis and characterization of titanium dioxide optical films by sol–gel processes

The main purpose of this study is to synthesize the front panel of monitor with a high refractive index optical film. Our experiment uses titanium dioxide nanoparticles mixed with methyl methacrylate (MMA), 2‐hydroxyethyl methacrylate (2‐HEMA), and tri(ethylene glycol) dimethacrylate (TEGDMA) of the wet type and economical sol–gel production process. Our product has a superior mechanical, thermal, and optical properties was demonstrated by Fourier transform infrared spectrum (FTIR), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UV/visible spectrum, and Spectro Ellipsometer. In addition, we found the surface of the two series of thin film with the organic and inorganic high refractive index (TiO₂) mixed materials, has high transmittance for visible light above 90%, refractive index <1.65 and the hardness test 6H. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2271–2280, 2007