Ferroelectric switching in spin-coated nylons 11 and 12

Here, we investigate the correlation between the crystal structures and the ferroelectric switching by a sinusoidal alternative electric field for spin-coated nylon 11 films as an odd nylon and for nylon 12 as an even nylon. These spin-coated nylons afforded thin films with thicknesses ranging from 101 to 125 nm. The obtained thin films were subjected to melt-quenching, melt-cooling down, annealing-quenching, or annealing-cooling down. These processes were notably related to the resulting crystal structures. In particular, the crystal structures involving twisted bonds in the molecular chains were significantly related to ferroelectricity in both nylon 11 and nylon 12. Namely, the vector component of the amide dipole moments is transverse to the direction of the molecular chains, which is induced by the presence of more twisted bonds and is significantly related to the remanent polarization P_r for both nylons. In nylon 11, the hydrogen bonding interaction between the intermolecular amide dipole moments in the α and δ crystal forms was weakened by the existence of more twisted bonds. In nylon 12, the nonpolar γ crystal form was transformed to a polarizable γ’ crystal form because of the existence of more twisted bonds. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48438.     

Freestanding Ag2S/CuS PVA films with improved dielectric properties for organic electronics

The prime goal of this work is to synthesize free‐standing polyvinyl alcohol (PVA) films doped with Ag₂S, CuS, Ag₂S/CuS alloy, and Ag₂S/CuS nanocomposites through the sol–gel route. The dependence of Ag₂S content in the PVA nanocomposite films on both the real and imaginary parts of the complex permittivity and loss tangent values was examined. An enhanced dielectric constant was achieved with minimum dielectric loss due to the insulating silica layer. By changing the Ag₂S content in Ag₂S/CuS PVA films, the AC conductivity is improved with pure Ag₂S nanoparticles exhibiting highest values of the order of 10^?6?10^?9 S/cm. The Cole–Cole parameters were calculated and the semicircles observed in the plots indicate a single relaxation process. The results suggest that these composite films are potential materials for embedded capacitor applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43568.     

Encapsulation of cinnamaldehyde into nanostructured chitosan films

Recently, bioactive chitosan films featuring naturally derived essential oils have attracted much attention due to their intrinsic antimicrobial properties and applicability to a broad range of applications. Previously, the ability to form thick (t > 100 µm), chitosan‐essential oil films via solution casting has been demonstrated. However, the fabrication of well characterized ultrathin films (t < 200 nm) that contain essential oils remain unreported. Here, we systematically investigate increasing the incorporation of an essential oil, cinnamaldehyde (CIN) into ultrathin chitosan films. Films with and without the surfactant Span^®80 were spin‐coated. Qualitatively, films exhibited well‐defined structural color, which quantitatively ranged from 145 to 345 nm thick. Release studies confirmed that a 6× higher release of CIN was enabled by Span^®80 versus the chitosan control films, 30 µg versus 5 µg, respectively. These results suggest that nanostructured chitosan‐CIN coatings hold potential to delay bacterial colonization on a range of surfaces, from indwelling medical device to food processing surfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41739.     

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.     

Preparation and characterization of new nanocomposite polymer films containing NiO nanofillers

Nanocomposite solid polymer films based on the poly(exo‐N‐phenyl‐7‐oxanorbornene‐5,6‐dicarboximide) (PPhONDI)/LiClO₄/NiO system have been designed, and the effect of inorganic NiO nanofiller in different amounts on the film properties has been examined. The exo‐PPhONDI/LiClO₄/NiO polymer system is the first solid nanocomposite polymer electrolyte film example based on a ring‐opening metathesis polymerization (ROMP) host polymer. The NiO nanoparticles were prepared by two‐step chemical syntheses, and the thermoplastic host polymer, exo‐PPhONDI, was synthesized via ROMP. Composite polymer films were prepared by the solution‐casting method. The amount of nanoparticles was varied from 1 to 15 wt % of NiO. The conductivity of the nanocomposite solid polymer systems was influenced by the NiO nanofiller concentration. The composite films based on exo‐PPhONDI ROMP polymer with the highest conductivity were achieved for the composition with 8 wt % of NiO nanofiller and 10 wt % of LiClO₄ dopant. The prepared films were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy (SEM). The SEM results showed that the filler was well distributed in the polymer matrix. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45938.     

Structure,electrical, dielectric,and optical investigation on polyvinyl alcohol/metal chloride nanocomposites

Different concentrations of metal chlorides/polyvinyl alcohol nanocomposites have been prepared by the typical solvent cast technique. The prepared samples were investigated by different techniques such as X‐ray diffraction, differential scanning calorimetry, and scanning electron microscope. DC and AC conductivities are examined at different temperatures and frequencies. An activation process was found in the DC conductivity versus temperature relation and the activation energy was calculated. The AC conductivity obeyed the ω^S power law. The behavior of S with temperature was studied. Various dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″) and loss tangent (tan δ) have been determined in the temperature range 303–443 K at different frequencies. The dielectric parameters were found to decrease with increasing frequency. The study of dielectric relaxation as a function of temperature at constant frequency shows two relaxation mechanisms. The optical band gaps and band tails were estimated from the measured absorption spectra. The applied photon energy found to affect the observed optical band gaps. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Low-frequency ferroelectric switching studies in PVDF thin films across Cu or (Ag/Cu)/PVDF/Cu capacitor structures

Ferroelectric switching dynamics of polyvinylidene fluoride (PVDF) thin films in Cu or (Ag/Cu)/PVDF/Cu capacitors are explored by varying PVDF film thickness, applied electric field amplitude (4.35–87.5 MV/m) and frequency (100 mHz–200 Hz). Comprehending spontaneous polarization and its dependence upon interfaces, an electric field is critical for organic ferroelectric memory devices. In this article, quasi-static current–voltage, and polarization–electric field measurements are used to explain the relationship between the coercive field, signal amplitude, and frequency. The observed coercivity enhancement at lower PVDF film thicknesses and with rising frequencies of the applied signal is discussed with Kolmogorov-Avrami-Ishibashi domain nucleation and growth model. The relation between domain growth and the top electrode layer is further discussed from the exponent parameters.     

Conductive polymer‐coated mesh films with tunable surface wettability for separation of oils and organics from water

Here, we reported the preparation of hydrophobic mesh films by coating conductive polymers including polyaniline and polypyrrole (PPy) onto stainless steel grid through a simple electrodepositing process by combination with modification of hydrophobic materials. The hydrophobic mesh films can be used for continual separation of oils and organics from water with high selectivity. Furthermore, mesh film with reversible switching wettability from hydrophobicity to hydrophilicity can be obtained by electrodepositing of PPy in the presence of perfluorooctanesulfonate dopants at different electric potential, which makes it possible to prepare functional mesh materials with remotely controllable surface wettability for selective absorption and purification. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40759.     

Cellulose nanofibrils in biobased multilayer films for food packaging

The aim of this study was to evaluate a thin, TEMPO‐oxidized (2,2,6,6‐tetramethylpiperidine‐1‐oxyl–mediated oxidation) cellulose nanofibril (CNF) coating as a barrier layer in multilayer packaging films together with biobased polyethylenes. The purpose was also to explore the possible interactions between food products and the biobased films, and to evaluate the feasibility of these films for packaging of dry foods. CNF provided the biobased multilayer films with an oxygen barrier suitable for both demanding food products and modified atmosphere packaging (MAP). The MAP pouches made of these multilayer films retained their atmosphere and shape and protected ground hazelnuts from further oxidation for the storage time used in this study. However, irradiation used to sterilize packed foods and aroma compounds from clove in particular impaired the oxygen barrier property of the CNF layer, while the water vapor barrier property of the multilayer films remained unaffected. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44830.     

Influence of electrochemical copolymerization conditions of 3‐methylthiophene and biphenyl on the morphology and nanomechanical properties of the films

The aim of this work is to synthesize novel 3‐methylthiophene (3MTh)/biphenyl (Biph) copolymer films by electropolymerization and study their mechanical properties through nanoindentation. The morphology, the chemical structure as well as the electrical conductivity of the copolymer films depended strongly on the electropolymerization conditions. It was found that the polymer deposition follow an instantaneous, two‐dimensional nucleation and growth mechanism leading to homogenous films. The copolymer films had higher Young modulus and nanohardness than poly(3‐methylthiophene) (3PMTh), indicating that the incorporation of Biph units within the P3MTh chain leads to a more densely packed structure and a more brittle polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42575.     

Thermoelectric performance of electrodeposited nanostructured polyaniline doped with sulfo‐salicylic acid

Conducting polymers, in present days, are considered to be potential thermoelectric (TE) materials. Among them polyaniline (PANI) is a promising candidate. Nanostructured polyaniline doped with organic dopant is electrodeposited and structurally characterized. Its transport properties are investigated for thermoelectric applications. The analysis of transmission electron microscopy image reveals that the sample is rod like nanostructure. This study shows that the type (inorganic/organic) of dopants plays an important role to influence the dimension of nanostructure and the electrical transport properties of PANI. In this study, organic dopant sulfosalicylic acid is proposed for enhancement of figure of merit through an increase in thermoelectric power and decrease in thermal conductivity. Compared to our earlier work the figure of merit evaluated is two orders higher than that of the inorganic dopant bismuth nitrate doped PANI. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39920.     

Flexible and transparent polymer/cellulose nanocrystal nanocomposites with high thermal conductivity for thermal management application

Polymeric materials play important roles in semiconductor technology and modern electronic devices. However, the weak thermal management capability of polymer seriously restricts the service life, reliability, and efficiency of devices. Consequently, inorganic or metallic thermally conductive fillers are added into polymers to make up the low thermal conductivity, but the optical transparency and flexibility always decrease or even disappear. Herein, we report transparent polymer nanocomposites comprising poly(vinyl alcohol) (PVA) and cellulose nanocrystal (CNC) with highly lateral thermal conductivity [about 5.7 W/(m·K)]. Such a high thermal conductivity is attributed to the aligned structure of CNC in PVA matrix and hydrogen-bond interaction between CNC and PVA. All the organic nanocomposites also present excellent electrical insulating performance and tensile properties. The transparent and flexible nanocomposites are promising in the thermal management applications of displays, next-generation wearable devices, sensors, and LEDs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48864.     

Combination of temperature and saturated vapor annealing for phase separation of block copolymer

Phase separation of block copolymer films is a perspective technique for the creation of nanostructured templates. The phase separation can be induced by thermal or vapor solvent annealing. However, a standardized and reproducible technique of the phase separation is still missing, even though many papers describing various experimental conditions. In this article we have tried to develop standardized and reproducible technique of the phase separation, which can be easily scaled up. For this purpose we used the combination of the thermal and vapor annealing of poly(styrene‐b‐4‐vinylpyridine) copolymer films on a glass substrate under static conditions. The technique was tailored by the choice of optimal solvent for the vapor annealing, based on the solvent–polymer interaction. Finally, the films were reconstructed by immersing in methanol or ethanol and stretching of the P4VP component during the reconstruction was investigated by the angle‐resolved X‐ray photoelectron spectroscopy. Morphology of the films was investigated by the atomic force microscopy and confocal microscopy. The kinetics of the phase separation was also studied. The presented combined technique of the thermal and vapor annealing can be easily temperature‐controlled for reproducibly obtaining the films of a desired morphology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41853.     

Preparation of transparent PMMA/Fe(IO3)3 nanocomposite films from microemulsion polymerization

Polymethyl methacrylate (PMMA)/Fe(IO₃)₃ nanocomposite thin films are obtained by in situ particle generation in microemulsions and subsequent photopolymerization of a mixture containing methyl methacrylate, trimethylolpropane triacrylate, and crystallized iron iodate (Fe(IO₃)₃) nanorods. Hyper‐Rayleigh scattering measurements combined with X‐ray diffraction, transmission electron microscopy, and dynamic light scattering are first used to probe in situ the crystallization kinetics of iron iodate nanorods in water‐in‐oil microemulsions prepared with methyl methacrylate as the oil phase and marlophen NP12 as a surfactant. Trimethylolpropane triacrylate is then added as a crosslinker before spin‐coating. Films are deposited on glass substrates for the nonlinear optical characterizations and on silicon wafers for the piezoelectric and mechanical measurements. Nanocomposite films treated by corona discharge are finally characterized through optical microscopy, laser Doppler vibrometry, and Brillouin spectroscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1203‐1211, 2013     

Enhanced dielectric properties of polyamide 11/multi‐walled carbon nanotubes composites

Composites with multi‐walled carbon nanotubes (MWNTs) involved in polyamide 11 (PA11) were prepared via a conventional melt blending method. The structure, morphology, crystallization behavior, electrical, and dielectric properties of composites were investigated. The results demonstrated that the dispersed uniformly MWNTs favored the formation of α crystal of PA11 when the composites were quenched from melt. The dielectric constant of composites was dependent on the electric field frequency and MWNTs content, and the highest value of dielectric constant was as high as 350 for the composite with 1.21 vol % MWNTs at 10³ Hz, accompanied by a low dielectric loss. The enhanced dielectric properties could be interpreted by the formation of abundant nanocapacitors within the composites and the interfacial polarization effect resulting from accumulation of charge carriers at the internal interfaces between MWNTs and PA11. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42642.     

Polymer porous thin films obtained by direct spin coating

Films of four different nanostructures, namely micelles, filled cylinders, ring‐shaped porous nanostructures and hollow cylinders, can be prepared easily in a straightforward and simple way by spin coating onto a silicon plate toluene solutions of poly(styrene‐block‐4‐vinylpyridine) copolymer containing formic acid of increasing concentration. Despite the enormous progress in preparation of porous polymers, most of them require multiple steps. In this sense, this method represents an effort to obtain not only porous thin films but also other bidimensional nanostructures in a very simple way. © 2017 Society of Chemical Industry     

Enhancement of the hydrophobicity of recycled polystyrene films using a spin coating unit

This article describes a technique for recycling polystyrene cups (PS_r) mixed with poly(butyl methacrylate) (PBMA) to produce PS_r/PBMA films and subsequently PS_r films by removing PBMA with a selective solvent (acetic acid), with the benefit of a reduction in environmental pollution generated by polystyrene waste. Removal of PBMA increases roughness, which generates a significant increase ( 34°) in the water contact angle, reaching its highest value at 128°. By increasing the hydrophobicity of surfaces, properties with important technical applications are acquired such as those used in antifouling paints, stain‐resistant surfaces, and surfaces that avoid the formation and accretion of ice on microelectronic devices. Roughness of PS_r/PBMA films is significantly affected by the concentration of both polymers and by the spin rate, reaching its highest value at 2% PS_r and 3% PBMA at 2000 . For optimal film deposition, a cheap spin coating unit was designed and built, with a price less than 4% of that of a commercially available spin coating unit. Lastly, it was found that the data obtained with our spin coating unit is described by the Meyerhofer model with accuracy of 88% ± 3%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45365.     

Enhancement of dielectric constants of epoxy thermosets via a fine dispersion of barium titanate nanoparticles

In this study, we examined a facile approach for achieving a fine dispersion of barium titanate (BT) nanoparticles (NPs) in epoxy thermosets. First, the surfaces of BT NPs were modified with poly(ε‐caprolactone) (PCL) via a surface‐initiated ring‐opening polymerization approach. We found that the PCL‐grafted BT NPs were easily dispersed in epoxy thermosets. The fine dispersion of the PCL‐grafted BT NPs in the epoxy thermosets was evidenced by transmission electron microscopy and dynamic mechanical thermal analysis. We found that the organic–inorganic nanocomposites displayed significantly enhanced dielectric constants and low dielectric loss compared to the control epoxy. The nanocomposites containing 14.1 wt % BT NPs possessed dielectric constants as high as at a frequency of 10³ Hz. The dielectric loss was measured to be 0.002 at a frequency of 10³ Hz. The improved dielectric properties are accounted for the fine dispersion of the BT NPs in the epoxy thermosets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43322.     

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.     

Electromechanical deformation and failure of multilayered films

Layer thickness was found to have a significant effect on the irreversible electromechanical deformation and the failure mechanism in polycarbonate (PC)/poly (vinylidene fluoride) (PVDF) multilayered films when subjected to an electrical impulse in a DC needle-plane configuration. Three distinct regions of behavior were observed. Region I comprised thick layer systems that exhibited only irreversible center deformation. The improvement to failure resistance compared to the monolithic films was attributed to the interphase between the two components. Region II films with an intermediate layer thickness showed both an irreversible center deformation and a treeing mechanism which were observed to simultaneously occur. The surface treeing mechanism, similar to the lightning treeing phenomena in nature, occurs only at impact rates. The tree morphology showed large amounts of plowing, indicating that this damage mechanism can dissipate a large amount of energy prior to electromechanical fracture of the film. Region III films comprise ultrathin layers in the nanoscale and showed no treeing. The unique interphase region between these ultrathin layers was estimated to be at least ten percent of the overall layered structure. These films behaved similar to monolithic materials with improved electromechanical failure characteristics. This work complements the enhanced dielectric performance of multilayer films observed in earlier investigations.