Poly(vinylidene fluoride), PVDF, and its copolymers are the family of polymers with the highest dielectric constant and electroactive response, including piezoelectric, pyroelectric and ferroelectric ...effects. The electroactive properties are increasingly important in a wide range of applications such as in biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others. For many of these applications the polymer should be in one of its electroactive phases. This review presents the developments and summarizes the main characteristics of the electroactive phases of PVDF and copolymers, indicates the different processing strategies as well as the way in which the phase content is identified and quantified. Additionally, recent advances in the development of electroactive composites allowing novel effects, such as magnetoelectric responses, and opening new applications areas are presented. Finally, some of the more interesting potential applications and processing challenges are discussed.
Polymer-based actuators: back to the future Martins, P; Correia, D. M; Correia, V ...
Physical chemistry chemical physics : PCCP,
07/2020, Letnik:
22, Številka:
27
Journal Article
Recenzirano
Odprti dostop
Polymer-based actuators play a key role in the area of smart materials and devices, and for this reason different polymer-based actuators have appeared in recent years and are implemented in a broad ...range of fields, including biomedical, optical or electronics, among others. Although it is possible to find more types, they are mainly classified into two main groups according to their different working principles: electromechanical - with electrical to mechanical energy conversion - and magnetomechanical - with magnetic to mechanical energy conversion. The present work provides a comprehensive and critical review of the recent studies in this field. The operating principles, some representative designs, performance analyses and practical applications will be presented. The future development perspectives of this interesting field will be also discussed. Thus, the present work provides a comprehensive understanding of the effects reported in the past, introduces solutions to the present limitations and, back to the future, serves as a useful guidance for the design of new polymer-based actuators aiming to improve their output performances.
This work demonstrates that polymer-based actuators play a key role in the area of smart materials and devices.
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•TiO2 nanoparticles were immobilized on PVDF-TrFE for photocatalytic degradation of tartrazine.•A solar photoreactor was used for the photocatalytic experiments.•The dependence of ...tartrazine concentration on photocatalysis efficiency was addressed.•The light intensity and the reusability of the of the TiO2/PVDF-TrFE membranes was tested.
Recalcitrant dyes present in effluents constitute a major environmental concern due to their hazardous properties that may cause deleterious effects on aquatic organisms. Tartrazine is a widely-used dye, and it is known to be resistant to biological and chemical degradation processes and by its carcinogenic and mutagenic nature. This study presents the use of TiO2 (P25) nanoparticles immobilized into a poly(vinylidenefluoride–trifluoroethylene) (P(VDF–TrFE)) membrane to assess the photocatalytic degradation of this dye in a solar photoreactor. The nanocomposite morphological properties were analyzed, confirming an interconnected porous microstructure and the homogeneous distribution of the TiO2 nanoparticles within the membrane pores. It is shown that the nanocomposite with 8wt% TiO2 exhibits a remarkable sunlight photocatalytic activity over five hours, with 78% of the pollutant being degraded. It was also demonstrated that the degradation follows pseudo-first-order kinetics model at low initial tartrazine concentration. Finally, the effective reusability of the produced nanocomposite was also assessed.
In the present paper we report and discuss the physicochemical properties of novel electrolyte membranes, based on poly(vinylidenefluoride-co-trifluoroethylene), PVdF-TrFE, and ...poly(vinylidenefluoride-co-hexafluoropropylene), PVdF-HFP, co-polymer hosts and the PVdF-TrFE/poly(ethylene oxide (PEO) blend as separators for lithium battery systems. The results have shown that the examined separator membranes, particularly those based on the PVdF co-polymers, are able to uptake large liquid amounts leading to high ionic conductivity values.
The phase transformation from α to β poly(vinylidene fluoride) (PVDF) through a stretching process at different temperatures was investigated. Samples of originally α-PVDF were stretched uniaxially ...at different temperatures at draw ratios from 1 to 5. The stretched samples were studied and characterized by infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The maximum β-phase content was achieved at 80°C and a stretch ratio of 5, but the samples still showed 20% of the original α-phase. Accompanying the phase transformation, an orientation of the polymer chains was observed. The stretching process also influenced the degree of crystallinity of the polymer. Poling of the samples also improves the α- to β-phase transformation.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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•A new method is provided for tissue engineering based on magnetoelectric materials.•It allows the implementation of scaffolds providing mechanical and/or electrical stimuli to the ...cells.•These stimuli are remotely stimulated by a magnetic field.•This method represents a platform for further research in the field.•It also represents a novel application of the magnetoelectric effect.
A novel approach for tissue engineering applications based on the use of magnetoelectric materials is presented. This work proves that magnetoelectric Terfenol-D/poly(vinylidene fluoride-co-trifluoroethylene) composites are able to provide mechanical and electrical stimuli to MC3T3-E1 pre-osteoblast cells and that those stimuli can be remotely triggered by an applied magnetic field. Cell proliferation is enhanced up to ≈25% when cells are cultured under mechanical (up to 110ppm) and electrical stimulation (up to 0.115mV), showing that magnetoelectric cell stimulation is a novel and suitable approach for tissue engineering allowing magnetic, mechanical and electrical stimuli.
The performance of piezoresistive materials based on carbon nanotube/poly(vinylidene fluoride), CNT/PVDF, composites prepared by spray printing is reported. It is shown that for a CNT concentration ...close to the percolation threshold, where the piezoresistive response is the largest, the electromechanical response, characterized by the gauge factor, reach values up to 4.4, similar to the values obtained for hot-pressing prepared materials. Further, it is demonstrated that tunnelling is the main mechanism responsible for the electrical response, independently of the preparation method of the material or the microstructural features. The large value of the gauge factor and the easy processing method demonstrates the suitability of these materials for cost effective and large-scale sensor applications.
Since the first magnetoelectric polymer composites were fabricated more than a decade ago, there has been a reluctance to use piezoelectric polymers other than poly(vinylidene fluoride) and its ...copolymers due to their well-defined piezoelectric mechanism and high piezoelectric coefficients that lead to superior magnetoelectric coefficients of >1 V cm
Oe
. This is the current situation despite the potential for other piezoelectric polymers, such as natural biopolymers, to bring unique, added-value properties and functions to magnetoelectric composite devices. Here we demonstrate a cellulose-based magnetoelectric laminate composite that produces considerable magnetoelectric coefficients of ≈1.5 V cm
Oe
, comprising a Fano resonance that is ubiquitous in the field of physics, such as photonics, though never experimentally observed in magnetoelectric composites. The work successfully demonstrates the concept of exploring new advances in using biopolymers in magnetoelectric composites, particularly cellulose, which is increasingly employed as a renewable, low-cost, easily processable and degradable material.Magnetoelectric materials by converting a magnetic input to a voltage output holds promise in contactless electrodes that find applications from energy harvesting to sensing. Zong et al. report a promising laminate composite that combines a piezoelectric biopolymer, cellulose, and a magnetic material.
The main theoretical models for evaluation of the dielectric constant of ceramic/polymer composites are summarized and applied to PZT/poly(vinylidene fluoride) and BaTiO3/poly(vinylidene fluoride) ...composites with varying filler concentration and size in order to evaluate the suitability of the models and the main interactions that are responsible for the composite dielectric behavior.
All models predict an increase in dielectric constant with increasing filler content. On the other hand, this increase is different for different models, showing the relative importance of the different interactions. Experimentally, the size of the inclusions plays an important role in determining the dielectric behavior of a composite, especially at the nanoscale. Effects occurring at the interface between the filler particles and the matrix become important as the relative surface area at the interface increases. Models not including fitting parameters do not properly represent the increase in dielectric constant with increasing filler content and none of them seem to properly represent the dielectric behavior of nanocomposites. In this way, the effects contemplated by the models – interactions between the particles, interactions with the field, depolarization factor or shape parameter – are not sufficient to account for the variations of the dielectric behavior related to the sizes of the particles.
•The most relevant theoretical models for the static dielectric constant are summarized.•The models are classified into three classes depending on their physical assumptions.•A critical analysis has been performed by fitting the models to a composite system.•The models account for the filler concentration effect on the dielectric constant.•The models fail to account for the filler size effect which is a relevant parameter.
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