Research

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11 pages, 3905 KiB

Open AccessArticle

Comparative Study of PVDF Sheets and Their Sensitivity to Mechanical Vibrations: The Role of Dimensions, Molecular Weight, Stretching and Poling

by Miroslav Mrlík, Josef Osička, Martin Cvek, Markéta Ilčíková, Peter Srnec, Danila Gorgol and Pavel Tofel

Nanomaterials 2021, 11(7), 1637; https://doi.org/10.3390/nano11071637 - 22 Jun 2021

Cited by 15 | Viewed by 2225

Abstract

This paper is focused on the comparative study of the vibration sensing capabilities of poly(vinylidene fluoride) (PVDF) sheets. The main parameters such as molecular weight, initial sample thickness, stretching and poling were systematically applied, and their impact on sensing behavior was examined. The [...] Read more.

This paper is focused on the comparative study of the vibration sensing capabilities of poly(vinylidene fluoride) (PVDF) sheets. The main parameters such as molecular weight, initial sample thickness, stretching and poling were systematically applied, and their impact on sensing behavior was examined. The mechanical properties of prepared sheets were investigated via tensile testing on the samples with various initial thicknesses. The transformation of the α-phase to the electro-active β-phase was analyzed using FTIR after applying stretching and poling procedures as crucial post-processing techniques. As a complementary method, the XRD was applied, and it confirmed the crystallinity data resulting from the FTIR analysis. The highest degree of phase transformation was found in the PVDF sheet with a moderate molecular weight (Mw of 275 kDa) after being subjected to the highest axial elongation (500%); in this case, the β-phase content reached approximately 90%. Finally, the vibration sensing capability was systematically determined, and all the mentioned processing/molecular parameters were taken into consideration. The whole range of the elongations (from 50 to 500%) applied on the PVDF sheets with an Mw of 180 and 275 kDa and an initial thickness of 0.5 mm appeared to be sufficient for vibration sensing purposes, showing a d₃₃ piezoelectric charge coefficient from 7 pC N⁻¹ to 9.9 pC N⁻¹. In terms of the d₃₃, the PVDF sheets were suitable regardless of their Mw only after applying the elongation of 500%. Among all the investigated samples, those with an initial thickness of 1.0 mm did not seem to be suitable for vibration sensing purposes. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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15 pages, 2259 KiB

Open AccessArticle

Formation of a Low-Density Liquid Phase during the Dissociation of Gas Hydrates in Confined Environments

by Lihua Wan, Xiaoya Zang, Juan Fu, Xuebing Zhou, Jingsheng Lu, Jinan Guan and Deqing Liang

Nanomaterials 2021, 11(3), 590; https://doi.org/10.3390/nano11030590 - 26 Feb 2021

Cited by 4 | Viewed by 1605

Abstract

The large amounts of natural gas in a dense solid phase stored in the confined environment of porous materials have become a new, potential method for storing and transporting natural gas. However, there is no experimental evidence to accurately determine the phase state [...] Read more.

The large amounts of natural gas in a dense solid phase stored in the confined environment of porous materials have become a new, potential method for storing and transporting natural gas. However, there is no experimental evidence to accurately determine the phase state of water during nanoscale gas hydrate dissociation. The results on the dissociation behavior of methane hydrates confined in a nanosilica gel and the contained water phase state during hydrate dissociation at temperatures below the ice point and under atmospheric pressure are presented. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) were used to trace the dissociation of confined methane hydrate synthesized from pore water confined inside the nanosilica gel. The characterization of the confined methane hydrate was also analyzed by PXRD. It was found that the confined methane hydrates dissociated into ultra viscous low-density liquid water (LDL) and methane gas. The results showed that the mechanism of confined methane hydrate dissociation at temperatures below the ice point depended on the phase state of water during hydrate dissociation. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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18 pages, 8020 KiB

Open AccessArticle

Towards Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene)-Based Soft Actuators: Films and Electrospun Aligned Nanofiber Mats

by Riccardo D’Anniballe, Andrea Zucchelli and Raffaella Carloni

Nanomaterials 2021, 11(1), 172; https://doi.org/10.3390/nano11010172 - 12 Jan 2021

Cited by 6 | Viewed by 2607

Abstract

In the pursuit of designing a linear soft actuator with a high force-to-weight ratio and a stiffening behavior, this paper analyzes the electrostrictive effect of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) polymer in the form of film and aligned electrospun nanofiber mat. An experimental setup is [...] Read more.

In the pursuit of designing a linear soft actuator with a high force-to-weight ratio and a stiffening behavior, this paper analyzes the electrostrictive effect of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) polymer in the form of film and aligned electrospun nanofiber mat. An experimental setup is realized to evaluate the electrostrictive effect of the specimens disjointly from the Maxwell stress. In particular, an uniaxial load test is designed to evaluate the specimens’ forces produced by their axial contraction (i.e., the electrostrictive effect) when an external electric field is applied, while an uniaxial tensile load test is designed to show the specimens’ stiffening properties. This electro-mechanical analysis demonstrates that both the film and the nanofiber mat are electrostrictive, and that the nanofiber mat exhibits a force-to-weight ratio ∼65% higher than the film and, therefore, a larger electrostrictive effect. Moreover, both the film and the nanofiber mat show a stiffening behavior, which is more evident for the nanofiber mat than the film and is proportional to the weight of the material. This study concludes that, thanks to its electro-mechanical properties, the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene), especially in the form of aligned electrospun nanofiber mat, has high potential to be used as electro-active polymer for soft actuators in biomedical and biorobotics applications. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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15 pages, 2825 KiB

Open AccessArticle

Vibration Sensing Systems Based on Poly(Vinylidene Fluoride) and Microwave-Assisted Synthesized ZnO Star-Like Particles with Controllable Structural and Physical Properties

by Mariem M. Chamakh, Miroslav Mrlík, Stephen Leadenham, Pavel Bažant, Josef Osička, Mariam Al Ali AlMaadeed, Alper Erturk and Ivo Kuřitka

Nanomaterials 2020, 10(12), 2345; https://doi.org/10.3390/nano10122345 - 26 Nov 2020

Cited by 9 | Viewed by 1869

Abstract

This study deals with the effect of zinc oxide (ZnO) star-like filler addition to the poly(vinylidene fluoride) (PVDF) matrix, and its effect on the structural and physical properties and consequences to the vibration sensing performance. Microwave-assisted synthesis in open vessel setup was optimized [...] Read more.

This study deals with the effect of zinc oxide (ZnO) star-like filler addition to the poly(vinylidene fluoride) (PVDF) matrix, and its effect on the structural and physical properties and consequences to the vibration sensing performance. Microwave-assisted synthesis in open vessel setup was optimized for the preparation of the star-like shape of ZnO crystalline particles. The crystalline and star-like structure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX). Furthermore, the PVDF-based composites were prepared using a spin-coating technique from solution. An investigation of the transformation of the α crystalline phase to the β crystalline phase of the neat PVDF matrix and with various filler concentrations was performed using Fourier-Transform infrared (FTIR) spectroscopy, which shows an enhanced β-phase from 44.1% to 66.4% for neat PVDF and PVDF with 10 wt.% of particles, respectively. Differential scanning calorimetry (DSC) measurements and investigation showed enhanced crystallinity and melting enthalpy of the composite systems in comparison to neat PVDF, since ZnO star-like particles act as nucleating agents. The impact of the filler content on the physical properties, such as thermal and dynamic mechanical properties, which are critical for the intended applications, were investigated as well, and showed that fabricated composites exhibit enhanced thermal stability. Because of its dynamic mechanical properties, the composites can still be utilized as flexible sensors. Finally, the vibration sensing capability was systematically investigated, and it was shown that the addition of ZnO star-like filler enhanced the value of the thickness mode d₃₃ piezoelectric constant from 16.3 pC/N to 29.2 pC/N for neat PVDF and PVDF with 10 wt.% of ZnO star-like particles. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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15 pages, 2987 KiB

Open AccessArticle

Ti₃C₂T_x MXene-Based Light-Responsive Hydrogel Composite for Bendable Bilayer Photoactuator

by Sifani Zavahir, Patrik Sobolčiak, Igor Krupa, Dong Suk Han, Jan Tkac and Peter Kasak

Nanomaterials 2020, 10(7), 1419; https://doi.org/10.3390/nano10071419 - 21 Jul 2020

Cited by 20 | Viewed by 5105

Abstract

Soft actuators based on hydrogel materials, which can convert light energy directly into mechanical energy, are of the utmost importance, especially with enhancements in device development. However, the hunt for specific photothermal nanomaterials with distinct performance remains challenging. In this study, we successfully [...] Read more.

Soft actuators based on hydrogel materials, which can convert light energy directly into mechanical energy, are of the utmost importance, especially with enhancements in device development. However, the hunt for specific photothermal nanomaterials with distinct performance remains challenging. In this study, we successfully fabricated a bilayer hydrogel actuator consisting of an active photothermal layer from incorporated Ti₃C₂T_x MXene in poly(N-isopropylacrylamide) p(NIPAm)hydrogel structure and a passive layer from the N-(2-hydroxylethylpropyl)acrylamide (HEAA) hydrogel structure. The uniform and effective incorporation of MXene into the NIPAm hydrogel structures were characterized by a battery of techniques. The light responsive swelling properties of the MXene-embedded NIPAm-based hydrogel demonstrated fully reversible and repeatable behavior in the light on–off regime for up to ten consecutive cycles. The effect of MXene loading, the shape of the actuator, and the light source effects on the bilayer NIPAm-HEAA hydrogel structure were investigated. The bilayer hydrogel with MXene loading of 0.3% in the NIPAm hydrogel exhibited a 200% change of the bending angle in terms of its bidirectional shape/volume after 100 s exposure to white light at an intensity of 70 mW cm⁻². Additionally, the bending behavior under real sunlight was evaluated, showing the material’s potential applicability in practical environments. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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19 pages, 12150 KiB

Open AccessArticle

Structure–Properties Relationship of Electrospun PVDF Fibers

by Klara Castkova, Jaroslav Kastyl, Dinara Sobola, Josef Petrus, Eva Stastna, David Riha and Pavel Tofel

Nanomaterials 2020, 10(6), 1221; https://doi.org/10.3390/nano10061221 - 23 Jun 2020

Cited by 59 | Viewed by 5756

Abstract

Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers’ morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- [...] Read more.

Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers’ morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- and micro-sized fiber diameters were prepared by a controlled and reliable electrospinning process. The fibers with diameters from 276 nm to 1392 nm were spun at a voltage of 25 kV–50 kV from the pure PVDF solutions or in the presence of a surfactant—Hexadecyltrimethylammonium bromide (CTAB). Although the presence of the CTAB decreased the fibers’ diameter and increased the electroactive phase content, the piezoelectric performance of the PVDF material was evidently deteriorated. The maximum piezoelectric activity was achieved in the fibrous PVDF material without the use of the surfactant, when a piezoelectric charge of 33 pC N⁻¹ was measured in the transversal direction on a mean fiber diameter of 649 nm. In this direction, the material showed a higher piezoelectric activity than in the longitudinal direction. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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17 pages, 5055 KiB

Open AccessArticle

Effect of Structure of Polymers Grafted from Graphene Oxide on the Compatibility of Particles with a Silicone-Based Environment and the Stimuli-Responsive Capabilities of Their Composites

by Monika Zygo, Miroslav Mrlik, Marketa Ilcikova, Martina Hrabalikova, Josef Osicka, Martin Cvek, Michal Sedlacik, Barbora Hanulikova, Lukas Munster, David Skoda, Pavel Urbánek, Joanna Pietrasik and Jaroslav Mosnáček

Nanomaterials 2020, 10(3), 591; https://doi.org/10.3390/nano10030591 - 24 Mar 2020

Cited by 15 | Viewed by 3212

Abstract

This study reports the utilization of controlled radical polymerization as a tool for controlling the stimuli-responsive capabilities of graphene oxide (GO) based hybrid systems. Various polymer brushes with controlled molecular weight and narrow molecular weight distribution were grafted from the GO surface by [...] Read more.

This study reports the utilization of controlled radical polymerization as a tool for controlling the stimuli-responsive capabilities of graphene oxide (GO) based hybrid systems. Various polymer brushes with controlled molecular weight and narrow molecular weight distribution were grafted from the GO surface by surface-initiated atom transfer radical polymerization (SI-ATRP). The modification of GO with poly(n-butyl methacrylate) (PBMA), poly(glycidyl methacrylate) (PGMA), poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) and poly(methyl methacrylate) (PMMA) was confirmed by thermogravimetric analysis (TGA) coupled with online Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Various grafting densities of GO-based materials were investigated, and conductivity was elucidated using a four-point probe method. Raman shift and XPS were used to confirm the reduction of surface properties of the GO particles during SI-ATRP. The contact angle measurements indicated the changes in the compatibility of GOs with silicone oil, depending on the structure of the grafted polymer chains. The compatibility of the GOs with poly(dimethylsiloxane) was also investigated using steady shear rheology. The tunability of the electrorheological, as well as the photo-actuation capability, was investigated. It was shown that in addition to the modification of conductivity, the dipole moment of the pendant groups of the grafted polymer chains also plays an important role in the electrorheological (ER) performance. The compatibility of the particles with the polymer matrix, and thus proper particles dispersibility, is the most important factor for the photo-actuation efficiency. The plasticizing effect of the GO-polymer hybrid filler also has a crucial impact on the matrix stiffness and thus the ability to reversibly respond to the external light stimulation. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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12 pages, 1695 KiB

Open AccessArticle

Renewable Fabric Surface-Initiated ATRP Polymerizations: Towards Mixed Polymer Brushes

by Wojciech Raj, Alessandro Russo, Yaoming Zhang, Julien Chapelat and Joanna Pietrasik

Nanomaterials 2020, 10(3), 536; https://doi.org/10.3390/nano10030536 - 17 Mar 2020

Cited by 4 | Viewed by 3091

Abstract

A totally new approach in the synthesis of mixed polymer brushes tethered on polyamide (PA) surfaces is presented herein. As a proof of concept, two types of homopolymers were synthesized in sequential surface-initiated atom transfer radical polymerization (SI-ATRP) reactions: poly(methyl methacrylate)/poly((2-dimethylamino)ethyl methacrylate) and [...] Read more.

A totally new approach in the synthesis of mixed polymer brushes tethered on polyamide (PA) surfaces is presented herein. As a proof of concept, two types of homopolymers were synthesized in sequential surface-initiated atom transfer radical polymerization (SI-ATRP) reactions: poly(methyl methacrylate)/poly((2-dimethylamino)ethyl methacrylate) and polystyrene /poly((2-dimethylamino)ethyl methacrylate). The ATRP initiator was immobilized on the surface through PA chain-end groups in two subsequent steps, separated by homo-polymerizations. The amount of the PA chains’ end groups available on the modified surface was tuned by the thermal rearrangement of the surface. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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13 pages, 4318 KiB

Open AccessArticle

Smart Non-Woven Fiber Mats with Light-Induced Sensing Capability

by Igor Krupa, Patrik Sobolčiak and Miroslav Mrlik

Nanomaterials 2020, 10(1), 77; https://doi.org/10.3390/nano10010077 - 31 Dec 2019

Cited by 4 | Viewed by 2569

Abstract

This article is focused on the facile procedure for 2D graphene oxide (GO) fabrication, utilizing reversible de-activation polymerization approach and therefore enhanced compatibility with surrounding polymer matrix. Such tunable improvement led to a controllable sensing response after irradiation with light. The neat GO [...] Read more.

This article is focused on the facile procedure for 2D graphene oxide (GO) fabrication, utilizing reversible de-activation polymerization approach and therefore enhanced compatibility with surrounding polymer matrix. Such tunable improvement led to a controllable sensing response after irradiation with light. The neat GO as well as surface initiated atom transfer radical polymerization (SI-ATRP) grafted particles were investigated by atomic force microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. To confirm the successful surface reduction, X-ray photoelectron spectroscopy and Raman spectroscopy was utilized. The composites in form of non-woven fiber mats containing ungrafted GO and controllably grafted GO with compact layer of polymer dispersed in poly(vinylidene-co-hexafluoropropylene) were prepared by electrospinning technique and characterized by scanning electron microscopy. Mechanical performance was characterized using dynamic mechanical analysis. Thermal conductivity was employed to confirm that the conducting filler was well-dispersed in the polymer matrix. The presented controllable coating with polymer layer and its impact on the overall performance, especially photo-actuation and subsequent contraction of the material aiming on the sensing applications, was discussed. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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8 pages, 4127 KiB

Open AccessCommunication

Bi-Ligand Modification of Nanoparticles: An Effective Tool for Surface-Enhanced Raman Spectrometry in Salinated Environments

by Anna Tycova, Karel Kleparnik and Frantisek Foret

Nanomaterials 2019, 9(9), 1259; https://doi.org/10.3390/nano9091259 - 05 Sep 2019

Cited by 7 | Viewed by 2622

Abstract

Elimination of massive aggregation of nanoparticles in the sample of high ionic strength is a prerequisite for the sensitive analysis through a surface-enhanced Raman spectrometry (SERS). We present a system of silver colloid modification composed of two thiolated modifiers (3-mercaptopropionic acid and thiolated [...] Read more.

Elimination of massive aggregation of nanoparticles in the sample of high ionic strength is a prerequisite for the sensitive analysis through a surface-enhanced Raman spectrometry (SERS). We present a system of silver colloid modification composed of two thiolated modifiers (3-mercaptopropionic acid and thiolated polyethylene glycol) both creating a strong Ag-S bond. At their optimal molar ratio, the polymer acts as a steric barrier preventing direct nanoparticle–nanoparticle interaction, while the low-molecular organic acid creates areas accessible for the analyte molecules. Thus, this approach is an excellent tool for sustaining both the colloidal stability and SERS sensitivity. The functionality of the system was demonstrated on the SERS analysis of myoglobin from a saline solution. The favorable creation of hot spots was achieved by laser-induced sintering. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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Review

Jump to: Research

22 pages, 5047 KiB

Open AccessReview

Smart Supramolecular Self-Assembled Nanosystem: Stimulus-Responsive Hydrogen-Bonded Liquid Crystals

by Bing Liu, Tao Yang, Xin Mu, Zhijian Mai, Hao Li, Yao Wang and Guofu Zhou

Nanomaterials 2021, 11(2), 448; https://doi.org/10.3390/nano11020448 - 10 Feb 2021

Cited by 20 | Viewed by 6740

Abstract

In a liquid crystal (LC) state, specific orientations and alignments of LC molecules produce outstanding anisotropy in structure and properties, followed by diverse optoelectronic functions. Besides organic LC molecules, other nonclassical components, including inorganic nanomaterials, are capable of self-assembling into oriented supramolecular LC [...] Read more.

In a liquid crystal (LC) state, specific orientations and alignments of LC molecules produce outstanding anisotropy in structure and properties, followed by diverse optoelectronic functions. Besides organic LC molecules, other nonclassical components, including inorganic nanomaterials, are capable of self-assembling into oriented supramolecular LC mesophases by non-covalent interactions. Particularly, huge differences in size, shape, structure and properties within these components gives LC supramolecules higher anisotropy and feasibility. Therefore, hydrogen bonds have been viewed as the best and the most common option for supramolecular LCs, owing to their high selectivity and directionality. In this review, we summarize the newest advances in self-assembled structure, stimulus-responsive capability and application of supramolecular hydrogen-bonded LC nanosystems, to provide novel and immense potential for advancing LC technology. Full article

(This article belongs to the Special Issue Stimuli-Responsive Nanosystems Based on Polymers and Hybrid Nanoparticles)

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