Terpolymer Films Research Articles

Ferroelectric terpolymer films with enhanced cooling efficiency: An integrated approach considering electrocaloric response and dielectric losses

Ferroelectric terpolymer films with enhanced cooling efficiency: An integrated approach considering electrocaloric response and dielectric losses

Enhanced electrocaloric effect in (Bi0.5Na0.5)TiO3-6BaTiO3 based relaxor ferroelectric nanocomposites by regulating Joule heating

Recently, electrocaloric effect (ECE)-based cooling technology has attracted a great deal of research attention. With a relatively high energy conversion efficiency (∼70 %) and no generating greenhouse gases, ECE-based cooling technology is suitable for use in the next generation of solid-state cooling devices. In this investigation, the PMMA layer was coated on the surface of (Bi0.5Na0.5)TiO3-6BaTiO3-1.5 %BiCoO3 (BNBT-BCO) nanofillers to reduce the Joule heat of BNBT-BCO/terpolymer (P(VDF-TrFE-CFE)) nanocomposite. From the ECE measurement result, the adiabatic temperature change (ΔT) of the BNBT-BCO@P/T-15 nanocomposite film reached 10.33 °C under 90 MV/m, which is 25 % higher than that of the BNBT-BCO/T-15 nanocomposite film (no PMMA coating, ∼8.29 °C) under the same electric field. In addition, the ΔT of the BNBT-BCO@P/T-15 nanocomposite film reached 17.52 °C under 150 MV/m at room temperature. This value is approximately 60 % higher than that of the pristine terpolymer films (ΔT ∼ 10.84 °C) and 17.4 % higher than that of BNBT-BCO@P/T-20 nanocomposite film (ΔT ∼ 14.92 °C). This work creates a new approach to using the surface coating on ceramic nanoparticles to reduce the Joule heat of the nanocomposites and improving the adiabatic temperature change (ΔT) and efficiency of ECE devices.

Operando Investigation of the Molecular Origins of Dipole Switching in P(VDF‐TrFE‐CFE) Terpolymer for Large Adiabatic Temperature Change

AbstractRelaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next‐generation solid‐state coolers. Under an electric field, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (ΔTECE). This work resolves the molecular origins of the large entropy change behind the electric field‐induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short‐range trans (T) conformation of the CF2‐CH2 dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding ΔTECE whenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G‐enriched terpolymer films exhibiting a 4.02 K ΔTECE at 60 MV m−1 and these films are employed to manufacture a 2‐layer‐cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2‐layer cascaded device made of fluoropolymers.

Directed Self-Assembly of Diamond Networks in Triblock Terpolymer Films on Patterned Substrates.

Block copolymers (BCPs) are particularly effective in creating soft nanostructured templates for transferring complex 3D network structures into inorganic materials that are difficult to fabricate by other methods. However, achieving control of the local ordering within these 3D networks over large areas remains a significant obstacle to advancing material properties. Here, we address this challenge by directing the self-assembly of a 3D alternating diamond morphology by solvent vapor annealing of a triblock terpolymer film on a chemically patterned substrate. The hexagonal substrate patterns were designed to match a (111) plane of the diamond lattice. Commensurability between the sparse substrate pattern and the BCP lattice produced a uniformly ordered diamond network within the polymer film, as confirmed by a combination of atomic force microscopy and cross-sectional imaging using focused ion beam scanning electron microscopy. The successful replication of the complex and well-ordered 3D network structure in gold promises to advance optical metamaterials and has potential applications in nanophotonics.

Nanometric and Macroscopic Electroactive Response of P(VDF-co-TrFE) Copolymers and P(VDF-ter-TrFE-ter-CTFE) Terpolymers

The knowledge and the improvement of the electric responsiveness of P(VDF-co-TrFE) copolymer and P(VDF-ter-TrFE-ter-CTFE) terpolymer films are essential for their application in electronic devices. Many factors affect the performances of these electroactive films, such as the chemical composition and the thermal treatment. In this article, the response to an external electric field of copolymer and terpolymer films at both the nanometric and macroscopic scales is studied. The response at the nanometric scale is analyzed by piezoresponse force microscopy on thin films (∼100 nm thick), while that at the macroscopic scale is analyzed by measuring the electric displacement–electric field loops on thick films (∼20 μm thick). The effect of the chemical composition (CTFE content) is found to be crucial, both at the nanometric and macroscopic scales, in defining the electroactive behavior of the samples, while the thermal treatment seems more exacerbated at the nanometric scale. The orientation, shape, and size of the crystalline lamellae affect the orientation of the electric dipoles, which are thus more or less sensitive to the applied electric field. The controlled growth of edge-on lamellar stacks, obtained after crystallization from the melt at low cooling rates, provides a better piezoresponse of the film.

Square arrays of vertically aligned nanoporous cylinders from a linear ABC triblock terpolymer

AbstractVertically oriented nanoporous cylinders, demonstrating an unprecedented alignment persistence, were produced within freestanding poly(1,1‐dimethyl silacyclobutane)‐block‐polystyrene‐block‐poly(2‐vinyl pyridine) (PDMSB‐b‐PS‐b‐P2VP) layers (~15 μm thick) blended with short PS‐b‐P2VP chains by combining the non‐solvent induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment. Here, the NIPS step allowed for the formation of an asymmetric and porous PDMSB‐b‐PS‐b‐P2VP film having a top surface exhibiting poorly‐defined nanopores while the subsequent SVA treatment enabled to produce a symmetric layer that possesses highly‐ordered cylindrical nanodomains arranged into a 27 nm period square array. As the unblended NIPS/SVA‐made PDMSB‐b‐PS‐b‐P2VP monoliths exhibited a mixed orientation of parallel and perpendicular cylinders, a blending strategy was used to achieve tetragonally‐packed PDMSB and P2VP nanodomains having an exceptional vertical alignment persistence. Such solvent‐annealed (3 h, CHCl3) PDMSB‐b‐PS‐b‐P2VP monoliths blended with 20 wt% of PS‐b‐P2VP chains showed a water permeance close to the value measured through their parent NIPS‐made terpolymer films having poorly‐ordered nanopores.

Optical properties of PVDF-TrFE and PVDF-TrFE-CTFE films in terahertz band

Polymers have enormous potential in the optoelectronic and biomedical fields due to flexibility, biocompatibility, and ease of fabrication. Recent developments in the use of terahertz (THz) waves for biomedical and security applications demand information on the optical properties of the polymers and polymer composites in this region. In the present work, transmission, refractive index (n), and extinction coefficient (k) of PVDF-TrFE (75/25 mol.) copolymer and PVDF-TrFE-CTFE (73/23/4 mol.) terpolymer films with different thicknesses (40 μm, 60 μm, 80 μm) are measured by the THz-TDS system (up to 1 THz). PVDF copolymer and terpolymer films show average transmission of more than 90% irrespective of thickness. The average refractive index of PVDF-TrFE (75/25 mol.) copolymer and PVDF-TrFE-CTFE (73/23/4 mol.) terpolymer films are 1.50 ± 0.04 and 1.45 ± 0.05 respectively. The estimated extinction coefficient is considerably low for both polymer films for frequencies less than 0.6 THz. The average indices for PVDF-TrFE and PVDF-TrFE-CTFE films are close, however, the loss in PVDF-TrFE films is larger than the PVDF-TrFE-CTFE films. High transmission, low loss and ferroelectric properties make these PVDF based polymers highly desirable in light-wave manipulation, flexible electronic and solar devices.

Ion-Specific Antipolyelectrolyte Effect on the Swelling Behavior of Polyzwitterionic Layers

In this study, we systematically investigate the interactions between mobile ions generated from added salts and immobile charges within a sulfobetaine-based polyzwitterionic film in the presence of five salts (KCl, KBr, KSCN, LiCl, and CsCl). The sulfobetaine groups contain quaternary alkylammonium and sulfonate groups, giving the positive and negative charges. The swelling of the zwitterionic film in the presence of different salts is compared with the swelling behavior of a polycationic or polyanionic film containing the same charged groups. For such a comparative study, we design cross-linked terpolymer films with similar thicknesses, cross-link densities, and charge fractions, but with varying charged moieties. While the addition of salt in general leads to a collapse of both cationic and anionic films, the presence of specific types of mobile anions (Cl-, Br-, and SCN-) considerably influences the swelling behavior of polycationic films. We attribute this observation to a different degree of ion-pair formations between the different types of anionic counterions and the immobile cationic quaternary alkylammonium groups in the films where highly polarizable counterions such as SCN- lead to a high degree of ion pairing and less polarizable counterions, such as Cl-, cause a low degree of ion pairing. Conversely, we do not observe any substantial effect of varying the type of cationic counterions (K+, Li+, and Cs+), which we assign to the lack of ion pairing between the weakly polarizable cations and the immobile anionic sulfonate groups in the films. In addition, we observe that the zwitterionic films swell with increasing ionic strength and the degree of swelling is anion dependent, which is in agreement with previous reports on the "antipolyelectrolyte effect". Herein, we explain this ion-specific swelling behavior with the different cation and anion abilities to form ion pairs with quaternary alkylammonium and sulfonate in the sulfobetaine groups.

Tuning the Relaxor–Ferroelectric Properties of Poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) Terpolymer Films by Means of Thermally Induced Micro- and Nanostructures

Tuning the Relaxor–Ferroelectric Properties of Poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) Terpolymer Films by Means of Thermally Induced Micro- and Nanostructures

Synthesis of a novel A-b-(B-co-C)-type terpolymer with a regioregular poly(3-hexylthiophene) segment and its application to intrinsically stretchable transistor memory

To date, a variety of organic semiconductors with high stretchability have been developed for applications in wearable electronic devices. However, there is still a problem of irreversible damage by repeated stretching/releasing cycles, resulting in a low lifetime for the devices. In this study, a novel A-b-(B-co-C)-type terpolymer, where A and B-co-C were regioregular poly(3-hexylthiophene) (P3HT) and poly(nbutyl acrylate-co-acrylic acid) segments, respectively, was successfully synthesized by the copper-catalyzed azide-alkyne cycloaddition reaction of α-chain-end-functionalized P3HT with an azide moiety and α-chain-end-functionalized poly(nbutyl acrylate-co-tbutyl acrylate) with an alkyne moiety, followed by deprotection of tbutyl groups with trifluoroacetic acid. The AFM and OM images of the terpolymer films showed that no cracks formed even when stretched up to 100%. This may be due to the synergistic effect of the low Tg-inducible nbutyl acrylate and hydrogen-bonding-inducible acrylic acid repeating units in the copolymer segment. In addition, the results of organic transistor memory using terpolymer thin films showed that the transferred/stretched electrets could preserve their device performance and produce stable bipolar charge trapping by applying electrical writing/erasing processes.

Influence of reaction compatibilization on mechanical and barrier properties of poly(lactic acid)/ethylene–methyl acrylate-glycidyl methacrylate terpolymer films

Influence of reaction compatibilization on mechanical and barrier properties of poly(lactic acid)/ethylene–methyl acrylate-glycidyl methacrylate terpolymer films

Spectroscopic study of D1–A–D2–A terpolymer films for optoelectronic applications

Several strategies have been considered in search of more efficient organic materials for charge transfer in photovoltaic devices. Among them, the integration of donor-acceptor (D-A) functional units on a conjugated copolymer has been widely applied. In this framework, we evaluated four terpolymers made up of donor moieties derived from 9,9-dioctylfluorene and 9-(heptadecan-9-yl)-9H-carbazole combined with 2,1,3-benzothiadiazole, the acceptor moiety, in different monomer ratios and polymerization routes (block and random microstructures). The preferred molecular orientation and charge transfer dynamics of the polymeric films were assessed by near edge X-ray absorption fine structure spectroscopy (NEXAFS) and resonant Auger electron spectroscopy (RAES) around the sulfur K-edge. Charge transfer times (τCT) were estimated by the Core-Hole Clock (CHC) method. Films with a high degree of organization were identified for the block terpolymer and random terpolymers with uneven amounts of donor units, showing a preferred orientation of the benzothiadiazole (BT) molecular plane parallel to the substrate surface. The values of τCT measured for all terpolymers were higher than those for typical polymers used in photovoltaic devices, which is not desirable for this type of optoelectronic application, but this may be correlated to the strong acceptor character of BT, the unit probed. To investigate the effect of film formation on the excited state behavior, steady-state and time-resolved photoluminescence measurements were also conducted. X-ray photoelectron spectroscopy (XPS) was employed to characterize the surface chemical composition of the terpolymer films. Based on the spectroscopic data the block copolymer appears to be the most suitable for the desired application.

Enhancing Electrostrictive Actuation via Strong Electrostatic Repulsion among Field-Induced Nanodomains in a Relaxor Ferroelectric Poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) Random Terpolymer

Electrostrictive polymers having a large strain are desirable for actuation, sensing, and energy harvesting in wearable electronics and soft robotics. However, a high electric field (>100 MV/m) is usually required for current electrostrictive polymers. To realize large electrostriction at reduced electric fields, the fundamental electrostriction mechanism needs to be better understood. In response to this need, the structure and electrostrictive properties of relaxor ferroelectric (RFE) poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] random terpolymers films with different thermal annealing histories were studied in this work. First, the semicrystalline structure of the P(VDF-TrFE-CTFE) terpolymer films was studied by combined small-angle X-ray scattering and wide-angle X-ray diffraction analyses. A three-phase model was employed, namely, crystals and oriented and isotropic amorphous fractions (OAF and IAF). The bulky CTFE units generated taut-tie molecules (TTM) in the crystalline lamella, dividing it into many nanosized crystals (∼1.3 nm thick). It is this unique crystalline structure with nanocrystals and mobile TTM/OAF that enabled the RFE behavior for the P(VDF-TrFE)-based terpolymers. Through electrostriction measurements and nonlinear dielectric analysis, an inverse correlation was observed between the ferroelectric nonlinearity and the electrostrictive coefficient under a high poling electric field (>100 MV/m). This suggested that higher electrostriction performance could be achieved by decreasing the ferroelectric nonlinearity of the RFE terpolymer. Indeed, above the Curie temperature, the paraelectric terpolymer films achieved a high electrostrictive performance with the transverse strain being ∼5% at 200 MV/m. This was attributed to the strong electrostatic repulsion among electric field-induced ferroelectric nanodomains. The finding from this work provides a viable way to design new electrostrictive polymers with higher performance at low driving fields.

Enhanced dielectric permittivity and relaxor behavior in thermally annealed P(VDF-TrFE) copolymer films

Modification of relaxor behavior and large enhancement in dielectric permittivity are demonstrated in a P(VDF-TrFE) ferroelectric polymer film by thermal annealing treatment. For coexisting normal ferroelectric and relaxor behavior in P(VDF-TrFE) (molar ratio: 45:55) films, the relative contribution from the relaxor component is increased when annealed at high temperature and subsequently quenched. A relative peak permittivity of ε′ ∼ 100 is obtained for an annealing temperature of T = 90 °C, which is one of the highest reported so far among poly(vinylidene fluoride) copolymer and terpolymer films. Based on x-ray diffraction analysis, we attribute the changes in dielectric properties to a decrease in crystallite domain size and a consequent increase in the crystalline-amorphous interfacial area.

Strong Circular Dichroism in Single Gyroid Optical Metamaterials

AbstractOver the past two decades, metamaterials have led to an increasing number of biosensing and nanophotonic applications due to the possibility of a careful control of light propagating through subwavelength features. Chiral nanostructures (characterized by the absence of any mirror symmetry), in particular, give rise to unique chiro‐optical properties such as circular dichroism and optical activity. Here, a gyroid optical metamaterial with a periodicity of 65 nm exhibiting a strong circular dichroism at visible wavelengths is presented. This bottom‐up approach, based on metallic replication of the gyroid morphology in triblock terpolymer films, generates a large area of periodic optical metamaterials. A strong circular dichroism in gold and silver gyroid metamaterials at visible wavelengths is observed. It is shown that the circular dichroism is inherently linked to the handedness of the gyroid nanostructure and its tuneability is demonstrated. The optical effects are discussed and compared to other existing systems, showing the potential of bottom‐up approaches for large‐scale circular filters and chiral sensing.

Electrosynthesis of Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole) Terpolymer and Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole)‐TiO2 Nanocomposite on Steel

AbstractPoly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole) (P(ANI‐co‐PY‐co‐NMP)) terpolymer film was synthesized in 0.30 M oxalic acid solutions containing 0.05 M aniline +0.05 M pyrrole +0.05 M N‐methylpyrrole. Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole)‐TiO2 nanocomposites were synthesized in 0.30 M oxalic acid solutions containing 0.05 M aniline +0.05 M pyrrole+0.05 M N‐methylpyrrole+0.1/0.4/1.0 gL−1 TiO2. Electrochemical syntheses were performed on the carbon steel (CS) elctrode using cyclic voltammetry technique. The terpolymer and nanocomposites were characterized by SEM, EDX, electrochemical impedance spectroscopy (EIS), open circuit potential‐time and anodic polarization techniques. Nanocomposite structures were observed after the addition of TiO2 nanoparticles into terpolymer films and these results was verified via EDX analysis. The results driven by EIS and anodic polarization suggest that, terpolymer and nanocomposite coated electrodes have been shown to have a protective effect against the corrosion of the CS electrode. The nanocomposite coated electrode synthesized in an environment containing 0.4 gL−1 TiO2 was found to have higher corrosion resistance in comparison to uncoated electrode, terpolymer coated electrode and electrodes coated with nanocomposites that is synthesized in environments containing 0.1/1.0 gL−1 TiO2. These results showed that the amount of TiO2 affects the anticorrosive properties of the synthesized nanocomposite.

Atmospheric pulsed plasma copolymerization of acrylic monomers: Kinetics, chemistry, and applications

AbstractIn this study, dimethylacrylamide (DMA) homopolymer and DMA/ethylene glycol dimethacrylate (DMA/EGDMA) copolymers are produced by an atmospheric pulsed plasma deposition technique. Such a mild deposition method is used to limit monomer fragmentations and favor cross‐linked structures formed through the unsaturated carbon double bond polymerization. The kinetics of deposition, and the dependence of the chemical and physical properties of the films on the comonomer ratio are investigated by combining surface and volume‐sensitive techniques. In addition, water‐stable catechol‐bearing terpolymer films are easily produced from a precursor mixture composed of dopamine methacrylamide dissolved in a 50 mol% DMA/EGDMA solution. Finally, it is demonstrated that the developed coatings can be exploited for efficient one‐step bioconjugation reaction for potential biological applications.

Conjugated donor–acceptor star molecules: a new concept for substantial dielectric breakdown strength improvement in PVDF films

Star-shaped molecules with donor–acceptor structures can significantly improve the BDS of PVDF terpolymer films.

Electrical polarization phenomena, dielectric relaxations and structural transitions in a relaxor-ferroelectric terpolymer investigated with electrical probing techniques

Dielectric Relaxation Spectroscopy (DRS) and Thermally Stimulated Depolarization Current (TSDC) measurements were employed to study dielectric-relaxation processes, structural transitions and electric-polarization phenomena in poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films. Results from DRS confirm the existence of two separate dispersion regions related to a para-to-ferroelectric phase transition and to the glass transition. The dipolar TSDC peak correlates with the loss peak of the α relaxation that represents the glass transition. The electric polarization calculated from the dipolar TSDC peak (glass transition) shows a non-linear electric-field dependence and saturates at high electric poling fields. As the observed behaviour is essentially the same as that of the electric polarization obtained from direct polarization-versus-electric-field hysteresis measurements, TSDC experiments are also suitable for studying the polarization in relaxor-ferroelectric polymers. A saturation polarization of 44 mC m−2 was found for an electric field of 190 MV m−1.

Complex core-shell morphologies of block copolymers revealed beneath the surface

This paper identifies and characterizes complex core-shell morphologies in thin films of a polybutadiene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (BVT) triblock terpolymer. The spin-coated BVT film develops into two distinct microphase separated structures with thickness variation during solvent annealing in a well-controlled atmosphere of THF vapor. Cylinders parallel to the film plane are found in thinner terraces and featureless areas that are characteristic of the lying lamella phase, or disordered structures are found in thicker terraces. Underneath the surface, we found that these microphase separated structures exhibit core-shell morphologies, i.e. surface ablation revealed core-shell cylinders and core-shell perforated lamellae under a cover layer in each terrace. Time-resolved study upon solvent annealing shows that the dynamics of microdomain evolution are affected by the extent of annealing time. The structural development in the BVT terpolymer films on corrugated supports demonstrates flow-field-induced sequenced ordering of the microdomains.