Terpolymer Films Research Articles

The application of a high-k polymer in flexible low-voltage organic thin-film transistors

Although much progress has been made in the study of high-mobility organic semiconductors in recent years, one major challenge for organic thin film transistors (OTFTs) in real applications is the relatively high operating voltage, which is mainly related to the gate dielectric of the OTFT. Here we show the application of a high-k poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) as the gate dielectric of flexible low-voltage pentacene OTFTs for the first time. The performance of the OTFTs is optimized by modifying the surface of P(VDF-TrFE-CFE) films with various thin polymer films by a solution process. The flexible OTFTs show excellent performance at the operating voltage of 4 V and good stability after 1000 bending tests. It is expected that P(VDF-TrFE-CFE) is a suitable gate dielectric for low-voltage OTFTs based on various small-molecule organic semiconductors because P(VDF-TrFE-CFE) terpolymer films can be easily modified with different thin polymer films by a solution process.

Core-free rolled actuators for Braille displays using P(VDF–TrFE–CFE)

Refreshable Braille displays require many small diameter actuators to move the pins. The electrostrictive P(VDF–TrFE–CFE) terpolymer can provide the high strain and actuation force under modest electric fields that are required for this application. In this paper, we develop core-free tubular actuators and integrate them into a 3 × 2 Braille cell. The terpolymer films are solution cast, stretched to 6 μm thick, electroded, laminated into a bilayer, rolled into a 2 mm diameter tube, bonded, and provided with top and bottom contacts. Experimental testing of 17 actuators demonstrates significant strains (up to 4%) and blocking forces (1 N) at moderate electric fields (100 MV m−1). A novel Braille cell is designed and fabricated using six of these actuators.

Tunable temperature dependence of electrocaloric effect in ferroelectric relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene terpolymer

The electrocaloric effect (ECE) was directly measured in a relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer. It was observed that the temperature dependence of ECE of the terpolymer films depends critically on the film preparation conditions. While the uniaxially stretched terpolymer films show pronounced temperature dependence of ECE, the non-stretched films exhibit nearly temperature independent ECE from 5 °C to 45 °C. Such a difference is likely caused by the changes in possible polar states and polar-correlation range by film stretching. Besides, large ECE (T > 15 °C) can be induced in both films at 30 °C and 150 MV/m.

Tuning Structure and Properties of Graded Triblock Terpolymer-Based Mesoporous and Hybrid Films

Despite considerable efforts toward fabricating ordered, water-permeable, mesoporous films from block copolymers, fine control over pore dimensions, structural characteristics, and mechanical behavior of graded structures remains a major challenge. To this end, we describe the fabrication and performance characteristics of graded mesoporous and hybrid films derived from the newly synthesized triblock terpolymer, poly(isoprene-b-styrene-b-4-vinylpyridine). A unique morphology, unachievable in diblock copolymer systems, with enhanced mechanical integrity is evidenced. The film structure comprises a thin selective layer containing vertically aligned and nearly monodisperse mesopores at a density of more than 10(14) per m(2) above a graded macroporous layer. Hybridization via homopolymer blending enables tuning of pore size within the range of 16 to 30 nm. Solvent flow and solute separation experiments demonstrate that the terpolymer films have permeabilities comparable to commercial membranes, are stimuli-responsive, and contain pores with a nearly monodisperse diameter. These results suggest that moving to multiblock polymers and their hybrids may open new paths to produce high-performance graded membranes for filtration, separations, nanofluidics, catalysis, and drug delivery.

Radiation‐Induced Graft Copolymerization of Styrene into Tetrafluoroethylene‐Hexafluoropropylene‐Vinylidene Fluoride (THV) Terpolymer Films

AbstractThe objective of this work was to investigate the influence of irradiation conditions on grafting of styrene into tetrafluoroethylene‐hexafluoropropylene‐vinylidene fluoride (THV) terpolymer films. Stress–strain measurements, infrared spectroscopy and electron paramagnetic resonance spectroscopy have been used to characterize the pre‐irradiated polymer films regarding tensile strength, elongation at break, changes in the chemical structure and concentration of trapped radicals, respectively. Main‐chain scissions associated with the formation of carbonyl end groups and end‐chain double bond structures have been identified to be the reason for a moderate deterioration of the mechanical properties of the pre‐irradiated films. The yield of grafting has been found to be influenced by THV grade, irradiation temperature and concentration of cross‐linker. magnified image

Thermal characterization of a series of poly(vinylidenefluoride–chlorotrifluoroethylene–trifluoroethylene) terpolymer films

A number of solution-casted poly(vinylidenefluoride–chlorotrifluoroethylene–trifluoroethylene) [P(VDF–CTFE–TrFE)] terpolymer films with different CTFE content have been characterized by a series of thermal analysis techniques, including thermogravimetric analysis (TG), differential scanning calorimetry, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA). The work intends to provide more comprehensive information about thermal behavior of these ferroelectric polymers. TG results suggest that the introduction of the CTFE units slightly decreases the thermal stability of the polymer due to the instability of C–Cl bond during heating. DMA detected a relatively weak αa relaxation and a broad αc relaxation in the samples of low CTFE content. These two relaxation processes completely mixed together in the sample with high CTFE content, revealing the crystalline structures in the polymer, become a more imperfect and diffuse state as CTFE units increasing. The polymer with less CTFE units possesses an enhanced stiffness due to its higher degree of crystallinity. A contraction process after a slight amount of thermal expansion upon heating is detected by TMA, due to the release of internal tensile strain/stress generated during solidification of the films. The higher crystallinity of the polymer film generated the greater strain/stress, leading to the larger degree of shrinkage. Also, the higher melting point of the polymer with less CTFE units allows the film soften at a higher temperature.

Transition from relaxor to ferroelectric-like phase in poly(vinylideneflouride-trifluoroethylene-chloroflouroethylene) terpolymer ultrathin films

The poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) terpolymer (56.2/36.3/7.5, mol %) films from 1.6 to 10 nm in thickness were prepared by the Langmuir–Blodgett method. The dielectric and ferroelectric properties of the terpolymer films were investigated. The phase transition of the films of less 3.2 nm in thickness exhibits a ferroelectric-like nature, which is inconsistent with the bulk terpolymers. The peak of the permittivity is at ∼360 K, which is much higher than the thick terpolymer films and it is independent on frequency. Both polarization-electric field and capacitance-voltage curves show a ferroelectric-like characteristic, which is confirmed by piezoresponse force microscopy, suggesting the presence of all-trans molecular conformation.

The Optical Dispersion of Langmuir-Blodgett Terpolymer Films

Relaxor ferroelectric terpolymer, Poly (vinylidene fluoride-trifluoroethylene-chlorofloroethylene) can be applied in many modern electronics systems. In this paper, the terpolymer films were deposited on aluminum-coated silicon substrates by horizontal Langmuir-Blodgett technology. The X-ray diffraction pattern indicates that the films have good crystallinity. The optical dispersion of the films were measured by variable-angle spectroscopic ellipsometry over a range from 300–1300 nm. The data Ψ and Δ at multiple incident angels (θ = 75° and 85°) were fitted using the Cauchy model. The refractive index n, the extinction coefficient k and the thickness of each film were obtained.

Going beyond the Surface: Revealing Complex Block Copolymer Morphologies with 3D Scanning Force Microscopy

We report on the quasi in situ scanning force microscopy nanotomography which proved to be a key method to effectively obtain a three-dimensional (3D) microdomain structure of a complex ABC triblock morphology. As an example, we studied polybutadiene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (BVT) thin triblock terpolymer films. We realized a controlled erosion of the material by using low-pressure plasma etching coupled to the scanning force microscope. The 3D reconstruction provides insights into the structural behavior in very thin volume elements revealing morphological details not accessible with other methods.

Huge electrocaloric effect in Langmuir–Blodgett ferroelectric polymer thin films

In this work, we studied polyvinylidene fluoride (PVDF)-based ferroelectric copolymer and terpolymer films grown, by the Langmuir–Blodgett (LB) technique, on polyimide substrates. The LB technique is believed to improve the film quality, i.e. to confer better crystallinity and less parasitic amorphous phase. As a consequence, a reversible adiabatic temperature change ΔT up to 21 K is demonstrated. The large electrocaloric effects of LB films close to room temperature suggest the potential for applying LB films in cooling systems.

Structure of Water in the Vicinity of Amphoteric Polymers as Revealed by Vibrational Spectroscopy

The water incorporated in a thin film of amphoteric terpolymers composed of various ratios of methacrylic acid (MA), N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) and n-butyl methacrylate was analyzed using the band shapes of the O–H stretching in the infrared spectra. At an early stage of sorption of water into the polymer film, the O–H stretching band for the water incorporated in the film with comparative contents of MA and DMAPMA residues was similar to that for bulk water. These results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the hydrogen-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups. The number of platelets adhered to the film with comparative contents of MA and DMAPMA residues was relatively the smallest among the examined terpolymer films, which suggested a correlation between the mildness of the charge-balanced polymeric materials to the structure of incorporated water and their blood-compatibilities. In addition, the structure and hydrogen bonding of water in an aqueous solution of co-polymers composed of various ratios of MA and DMAPMA or [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were also analyzed using the contours of the O–H stretching in the polarized Raman spectra. The number of hydrogen bonds disrupted due to the presence of one monomer residue (N corr value) for PolyMA was largely positive, and with an increase in the content of the DMAPMA or MAPTAC residues, the N corr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the N corr value increased again. This is in a significant contrast with the largely positive N corr values for the homo-polymers (PolyMA, PolyDMAPMA and PolyMAPTAC), and other ordinary polyelectrolytes. The effect of the charge-balanced co-polymer on the hydrogen-bonded network structure of vicinal water observed by Raman spectroscopy was in accordance with that of the charge-balanced terpolymer film observed by infrared spectroscopy.

The effect of ac field amplitude on the relaxor behaviors in Langmuir–Blodgett terpolymer films

The ac field (Eac) amplitude dependence of dielectric response has been investigated for poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor terpolymer films. The frequency dependence of the temperature of the permittivity maximum Tm can be well described by the Vogel–Fulcher relation for Eac in the range from 1.33 to 80 MV/m. Tm remains nearly constant at an Eac level lower than 13.3 MV/m, and starts decreasing with Eac increases further. The two parameters fitting to the Vogel–Fulcher relation, freezing temperature Tf and activation energy Ea, vary little for Eac below 26.7 MV/m and then Tf decreases, while Ea increases for higher Eac level.

Threshold fields in the dc bias dependence of dielectric responses of relaxor ferroelectric terpolymer films

The dc bias dependence of dielectric properties has been investigated for poly (vinylindene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor terpolymer films. The frequency dependence of the temperature of the permittivity maximum, Tm, was analyzed using the Vogel–Fulcher (VF) relation. Two threshold fields, ∼30 and 160 MV/m were found in the electric-field dependence of Tm. Tm shows a minimum at ∼30 MV/m and a maximum at ∼160 MV/m. The VF parameters activation energy Ea and freezing temperature Tf respectively show a maximum and a minimum at ∼25 MV/m.

Mechanical flexible and electric fatigue resistant behavior of relaxor ferroelectric terpolymer

Uniaxial tension and polarization evolution under cyclic electric field are investigated for poly(vinylidene fluoride-trifluorethylene-chlorofluoroethylene) terpolymer films prepared by different annealing conditions. The stress-strain behavior of the terpolymer film exhibits that of polymeric elastomers, with its fracture strain reaching 680%. Structure analysis demonstrates that the polymer chains undergo reorientation, and conformational change from nonpolar to polar phase takes place during uniaxial tension. Under cyclic electric field, the terpolymer film exhibits a narrow polarization loop typical of a ferroelectric relaxor. Conformational change from nonpolar to polar phase also occurs upon the electric field, and it reverses to the nonpolar phase when the field is removed. As the cycle number accumulates, the terpolymer film demonstrates excellent resistance to electric fatigue. Compared to the film annealed at 115 °C, the terpolymer film annealed at 100 °C has a larger volume fraction of crystallite/amorphous interfaces and shows better mechanical flexibility as well as electric fatigue resistance. The mechanical flexible and electric fatigue resistant terpolymer films hold promises for many applications, ranging from embedded sensors and actuators to flexible memory devices.

Study of the physicochemical properties of aminostyrene copolymers modified by plasma treatment

The change in the surface and mechanical properties of styrene-butyl methacrylate-aminostyrene terpolymer films by plasma treatment was investigated. It was found that treatment in a direct-current discharge enhanced the mechanical strength of the terpolymer surface, which can be associated with the crosslinking of linear macromolecules into a three-dimensional network structure. It was shown that the most substantial changes in the mechanical strength are achieved in the case of terpolymer film treatment at the anode.

High electric tunability of relaxor ferroelectric Langmuir–Blodgett terpolymer films

Poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) terpolymer films have been fabricated on Al-coated polyimide substrates using the Langmuir–Blodgett (LB) technology. The electrical properties of the films have been investigated from 150 to 350 K. The temperature of the dielectric maximum and the measured frequency obeys the Vogel–Fulcher [J. Am. Ceram. Soc. 8, 339 (1925); Phys. Z. 22, 645 (1921)] law. The electric tunabilities of the films at room temperature are 42.6% and 80% under 50 and 240 MV/m, respectively. The reasons for the high tunability are discussed based on the special microstructure of the LB films.

A compact electroactive polymer actuator suitable for refreshable Braille display

The large strain, high elastic modulus, and easy processing of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) electrostrictive terpolymer make it very attractive to replace low strain piezoceramics and piezopolymers in many applications with much improved performance. In this paper, a compact polymer actuator is developed utilizing the electrostrictive terpolymer, which is suitable for full page Braille display and graphic display. Key issues related to the reliability of electroactive polymers used in the compact actuators and for the mass fabrication of these polymer actuators are investigated. Making use of a recently developed conductive polymer, a screen printing deposition method was developed which enables direct deposition of very thin conductive polymer electrode layer (<0.1 μm) with strong bonding to the terpolymer surface and short fabrication time. It was observed that the thin conductive polymer electrodes lead to the self-healing of the polymer after electric breakdown. An electroactive polymer (EAP) compact Braille actuator was designed and fabricated with these terpolymer films wound on a spring core. The test results demonstrate that the EAP Braille actuator meets all the functional requirements of actuators for refreshable full Braille display, which offers compact size, reduced cost and weight.

Effect of metal-polymer interface on the breakdown electric field of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer

The authors investigate the effect of electrode material and charge injection on the breakdown electric field of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer. The results indicate that the breakdown is mainly initiated at electrode-polymer interfaces, the properties of which are controlled by metal materials and deposition conditions. Interfaces with lower leakage currents display higher breakdown fields. Terpolymer films with Al and Cr electrodes have lower leakage current and higher breakdown field compared to those with Au and Ag electrodes. The difference in charge injection and breakdown field is attributed to both the existence of interfacial blocking layers and the difference in Schottky barrier height.

Synthesis and Characterization of Poly[((maleic anhydride)‐alt‐styrene)‐co‐(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)

AbstractSummary: Novel polyfunctional sulfone‐ and anhydride‐containing reactive terpolymers with different compositions have been synthesized by complex‐radical polymerization of the ternary MA‐St‐APMS acceptor‐donor‐acceptor monomer system. This method allows preparing terpolymers with a sufficiently high content of APMS which essentially increased polyelectrolyte, swelling, IEC and thermal stability of terpolymer films. The terpolymer structure‐composition‐properties (polyelectrolyte, thermal, swelling and cation exchange behavior) relationships were studied by FTIR and 1H{13C} NMR (DEPT‐135) spectroscopy, viscometry, DSC‐TGA methods, and by means of swelling and exchange capacity. The observed H‐bonding between sulfonic acid, amide and anhydride fragments played an important role in the formation of the physically crosslinked and self‐assembled architectures with controllable hydrophilic‐hydrophobic balance. These reactive terpolymers can be used as synthons for exchange membrane preparation and fuel cell applications.Physically crosslinked and self‐assembled macrocomplex.imagePhysically crosslinked and self‐assembled macrocomplex.

Terpolymer films having semipolar structure: Preparation, wettability, and mechanical properties

AbstractA terpolymer, obtained by the free‐radical terpolymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMMA), methyl methacrylate(MMA), and isobutyl methacrylate (IBMA), was allowed to react with hydrogen peroxide, chloroacetic acid, and diethyl sulfate to form the corresponding modified terpolymers: (1) N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)amine N‐oxide, MMA and IBMA (DMANO series); (2) N‐(carboxymethyl)‐N,N‐dimethyl‐ N‐(2‐methacryloyloxyethyl)ethyl ammonium, MMA and IBMA (CDME series); and (3) N‐(ethyl)‐N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)ethyl ammonium ethylsulfonate, MMA and IBMA (EDMEES series), respectively. The terpolymer compositions were determined using 13C NMR spectrometry. Surface free energies of the terpolymers were estimated by measuring the contact angles of water and methylene iodide on the three series films (DMANO, CDME, and EDMEES), and the effect of the N‐oxide group on wettability was discussed. It was found that the upper surface of the films for the DMANO and CDME series are more hydrophobic than that for the EDMEES series. Notably, elongation to break for the DMANO series was relatively larger than that for the CDME series because of the water bound to the N‐oxide functional group. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1235–1243, 2005