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1.
ACS Appl Mater Interfaces ; 16(9): 11595-11604, 2024 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-38381554

RESUMO

Dielectric elastomer generator (DEG), which consists of a dielectric elastomer (DE) film sandwiched between two flexible electrodes (FEs), has the advantages of lightweight, high energy density, and high energy conversion efficiency, providing a simple and feasible solution for harvesting energy from human motion or nature. As crucial constituents of DEG, FEs are expected to possess excellent conductivity and compliance. Nevertheless, there is currently no quantitative characterization method for FE compliance. In addition, the impact mechanism of FE compliance on the energy harvesting performance and fatigue life of the DEG remains unclear. In this study, the dynamic mechanical property (DMP) was used to assess the compliance of FEs, and the quantitative characterization method of FE compliance was proposed. A series of silicone rubber electrodes (SREs) with different DMPs and compliance were designed and prepared, and the impact mechanism of FE compliance on the energy harvesting stability and fatigue life of the DEG was investigated. The results indicate that the key to achieving excellent FE compliance lies in reducing the difference in the magnitude of the complex modulus and phase angle between the FEs and DE, which can significantly reduce interfacial friction and extend the fatigue life of DEG. Benefiting from the enhanced FE compliance, the fatigue life and full-life energy density of the DEG device increase by 20.3 times and 26.4 times, respectively, compared with those of the commonly used carbon-based electrodes.

2.
ACS Nano ; 18(1): 1226-1236, 2024 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-38153997

RESUMO

Dielectric elastomer transducers (DETs), with a dielectric elastomer (DE) film sandwiched between two compliant electrodes, are highly sought after in the fields of soft robotics, energy harvesting, and human-machine interaction. To achieve a high-performance DET, it is essential to develop electrodes with high conductivity, strain-insensitive resistance, and adaptability. Herein, we design an electrode (Supra-LMNs) based on multiple dynamic bond cross-linked supramolecular networks (Ns) and liquid metal (LM), which realizes high conductivity (up to 16,000 S cm-1), negligible resistance changes at high strain (1.3-fold increase at 1000% strain), instantaneous self-healability at ambient temperature, and rapid recycling. The conductive pathway can be activated through simple friction by transmitting stress through the silver nanowires (AgNWs) and cross-linking sites of LM particles. This method is especially attractive for printing circuits on flexible substrates, especially DE films. Utilized as dielectric elastomer generator (DEG) electrodes, it reduces the charge loss by 3 orders of magnitude and achieves high generating energy density and energy conversion efficiency on a low-resistance load. Additionally, serving as sensor (DES) and actuator (DEA) electrodes, it enables a highly sensitive sensing capability and complex interaction.

3.
Macromol Rapid Commun ; 44(13): e2300097, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37165710

RESUMO

Intelligent fluorescent coatings have received widespread attention in the encryption technique field such as anti-counterfeit, while the traditional fluorescent coatings are easy to be damaged by external force. In this study, the fluorescent and self-healing anti-counterfeit coatings are prepared after rational molecular design. Two polymers containing fluorescent groups, including polyurethane containing the anthracene (AN) side group and polyimide containing the naphthalenediimide (NDI) structure are synthesized to realize multiple color changes with fluorescence through simply blending. Due to the overlapping fluorescence spectra of the groups, enabling the fluorescence resonance energy transfer effect (FRET), the coating with different group ratios exhibits tunable fluorescence under the same excitation light, providing diverse patterns. Moreover, due to the reversible photo-crosslinking and thermal de-dimerization properties of anthracene, the recording, erasure, and rewriting of the surface pattern can be realized, and the fluorescent anti-counterfeit coatings exhibit excellent self-healing properties after cross-linking due to the FRET effect, which solves the problem of poor healing and ensures the stability and integrity. The fluorescent coating with cross-linked structure and self-healing behavior based on the FRET effect greatly expands the functional applications of traditional polyurethane materials.


Assuntos
Transferência Ressonante de Energia de Fluorescência , Poliuretanos , Transferência Ressonante de Energia de Fluorescência/métodos , Polímeros/química , Fenômenos Mecânicos , Corantes , Antracenos
4.
ACS Appl Mater Interfaces ; 15(19): 23963-23970, 2023 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-37158003

RESUMO

Highly immiscible blend materials with distinctive and excellent properties play a key role in meeting the application needs, especially in extreme environments, and reactive nanoparticles are used to increase the interface adhesion and optimize the morphology of highly immiscible blending. However, these reactive nanoparticles tend to aggregate and even agglomerate during reactive blending, which significantly deteriorates their compatibilization efficiency. Herein, reactive Janus particles with the epoxy group and various siloxane molecular long chain grafting ratios (E-JP-PDMS) were synthesized using SiO2@PDVB Janus particles (JP) and used as compatibilizers for polyamide and methyl vinyl silicone elastomer (PA/MVQ) blends, which were highly immiscible. The effects of the structure of E-JP-PDMS Janus nanoparticles on their location at the interfaces between the PA and MVQ as well as their compatibilization efficiency for the PA/MVQ blends were investigated. The location and dispersion of E-JP-PDMS at the interfaces were improved by increasing the PDMS content in E-JP-PDMS. The average diameter of the MVQ domains of the PA/MVQ (70/30, w/w) was 79.5 µm and was reduced to 5.3 µm in the presence of 3.0 wt % of the E-JP-PDMS with 65 wt % PDMS. As a comparison, it was 45.1 µm in the presence of 3.0 wt % of a commercial compatibilizer (ethylene-butylacylate-maleic anhydride copolymer, denoted as EBAMAH), which provides a guideline for the design and preparation of efficient compatibilizers for highly immiscible polymer blends.

5.
Adv Mater ; 35(22): e2300246, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36932852

RESUMO

Dielectric elastomer generators (DEGs) with high generated energy density and high conversion efficiency are of great interest. Among several dielectric elastomers (DEs), silicone elastomer filled with ceramic fillers have been extensively studied for their high elasticity, insulation, and permittivity. However, the stretched breakdown strength (Ebs ) of such composites decreases significantly under large strain, thus sharply reduces its energy harvesting performances. In this study, a polar rubber-based dielectric (GNBR) is synthetized and creatively used as "soft filler" for silicone elastomer. Benefiting from the deformability under stretching and its inherent strong interface bonding with silicone elastomer, this soft filler effectively avoids the formation of weak interface under large strain and reduces the local field strength of interface area. As expected, the composite filled with soft filler (GNBR/PMVS) shows enhanced Ebs of 2.8 times that of composite with traditional hard filler (TiO2 /PMVS) under equibiaxial strain of 200%. As a result, GNBR/PMVS composite exhibits maximum energy density of 130.5 mJ g-1 with up-to-date highest power conversion efficiency of reported DEG (44.5%). The findings will provide new insights in the rational design of DE composites characterized by high stretched breakdown strength for advanced energy harvesting system.

6.
Polymers (Basel) ; 13(23)2021 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-34883708

RESUMO

The dielectric elastomer (DE) generator (DEG), which can convert mechanical energy to electrical energy, has attracted considerable attention in the last decade. Currently, the energy-harvesting performances of the DEG still require improvement. One major reason is that the mechanical and electrical properties of DE materials are not well coordinated. To provide guidance for producing high-performance DE materials for the DEG, the relationship between the intrinsic properties of DE materials and the energy-harvesting performances of the DEG must be revealed. In this study, a simplified but validated electromechanical model based on an actual circuit is developed to study the relationship between the intrinsic properties of DE materials and the energy-harvesting performance. Experimental verification of the model is performed, and the results indicate the validity of the proposed model, which can well predict the energy-harvesting performances. The influences of six intrinsic properties of DE materials on energy-harvesting performances is systematically studied. The results indicate that a high breakdown field strength, low conductivity and high elasticity of DE materials are the prerequisites for obtaining high energy density and conversion efficiency. DE materials with high elongation at break, high permittivity and moderate modulus can further improve the energy density and conversion efficiency of the DEG. The ratio of permittivity and the modulus of the DE should be tailored to be moderate to optimize conversion efficiency (η) of the DEG because using DE with high permittivity but extremely low modulus may lead to a reduction in η due to the occurrence of premature "loss of tension".

7.
ACS Appl Mater Interfaces ; 12(5): 6426-6435, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31940167

RESUMO

Medical fixing is one of the very important applications of the shape-memory polymer material, and the two important properties of the medical fixing material are that it perfectly fits the body during the fixing and easily detaches after being used. As the fixing and detachment are triggered by two independent stimuli in two opposite directions, it is necessary to develop multidirectional triple-shape-memory polymers. In this research, a series of polymer materials composed of trans-polyisoprene (TPI) and paraffin were prepared by melt blending and compression molding, and then the TPI was cross-linked by vulcanization. As a result of the large difference in the melting temperature and crystallization temperature between TPI and paraffin, the obtained polymer materials exhibit a triple-shape-memory behavior. According to the analysis of crystal behavior, microscopic morphology, and mechanical properties of the materials with different paraffin contents and TPI cross-linking density by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and dynamic mechanical thermal analysis, the shape-memory behavior of the obtained materials was tunable by the cross-linking density of TPI and the crystallization degree of TPI or paraffin. Compared with the traditional triple-shape-memory material, our samples are prepared in a more facile way and can recover at human body temperature (37 °C). Moreover, our TPI/paraffin material can realize more flexible multidirectional recovery, as well as can be reprogramed and used multiple times. To the best of our knowledge, there are few polymer materials reported, which can realize multidirectional recovery. These unique multidirectional and reprogramable properties will enable the application of this polymer material, especially in the medical fixing materials.

8.
Soft Matter ; 16(9): 2185-2198, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-31909411

RESUMO

It is well-known that a fine dispersed rubber phase in thermoplastic vulcanizates (TPVs) is a key to obtain good mechanical properties and high elasticity of TPV products. Previous studies reported that the rubber nanodroplets formed during shearing blending can transform into rubber nanoparticles by in situ rapid crosslinking and these rubber nanoparticles spontaneously form agglomerates dispersed in a plastic matrix during dynamic vulcanization (DV). However, important influencing factors on the formation of rubber nanoparticles and their agglomeration during DV have not been reported yet. In this study, the coupling effect of the molecular weight (MW) of polypropylene (PP) and crosslinking kinetics including the crosslinking rate (CR) and crosslinking degree (CD) on the size of ethylene propylene diene monomer (EPDM) rubber nanoparticles and their agglomerates in EPDM/PP TPVs was systematically studied for the first time. The minimum diameter of EPDM nanodroplets was theoretically calculated by using the critical break-up law of viscoelastic melts for the blend with high MW PP or the critical capillary equation for the blend with low MW PP, and the real size of the EPDM nanoparticles was experimentally verified. Interestingly, the results show that the lower MW of the PP phase, lower CD and higher CR contribute to the formation of smaller rubber nanoparticles, whereas the higher MW of the PP phase and higher CD of the rubber phase contribute to the formation of smaller rubber nanoparticle agglomerates. This study provides guidance to optimize the microstructure of EPDM/PP TPVs for the preparation of high-performance TPV products.

9.
ACS Appl Mater Interfaces ; 11(51): 48321-48330, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31755684

RESUMO

A highly stretchable conductor was fabricated through dip-coating a new liquid metal (LM) electric ink on a polydopamine (PDA)-modified three-dimensional (3D) polyurethane sponge (PUS) followed by mechanical sintering. The LM was first sonicated to nanodroplets to reduce the consumption of LM and then modified by 3-mercaptopropionic acid (LMNPS-MPA) to improve the interfacial adhesion between LM and PUS. The denser and even distribution of LMNPS-MPA self-assembling on PDA-treated PUS (PUS-PDA) was successfully prepared via hydrogen bonding interactions. Mechanical sintering of 3D PUS-PDA coated by a two-dimensional (2D) LM layer was then conducted to obtain a continuous conductive network. Comparing with those of the reported 3D conductors, the resulting PUS-PDA-LM composite conductor shows both high electrical conductivity (478 S cm-1) under a low LM consumption of 10 vol% and excellent conductivity stability with the relative resistance change, ΔR/R0, of 2% at 50% strain under stretching deformation. The as-prepared PUS-PDA-LM composites were then successfully applied as flexible and stretchable light-emitting diode (LED) arrays with excellent conductivity and conductivity stability at different deformations. We believe that the 3D stretchable PUS-PDA-LM conductor has many potential applications in flexible sensors, flexible circuits, rollable displays, etc.

10.
ACS Appl Mater Interfaces ; 11(1): 1469-1479, 2019 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-30592610

RESUMO

Photothermal-induced self-healable and shape memory materials have drawn much attention due to the rapidly growing technical applications and environmental requirements. As epoxy natural rubber (ENR) is a kind of bio-based elastomer with good mechanical properties, weather resistance, and air impermeability, it is of great significance to incorporate ENR with recyclable, photothermal-induced self-healable and shape memory properties. In this study, we report a simple method to cross-link ENR with dodecanedioic acids (DAs) through esterification reaction, and during the cross-linking process, a little aniline trimer (ACAT, a kind of oligoaniline) was added at the same time. Then, the ENR-DA-ACAT vitrimers that were covalently cross-linked with recyclable, self-healable, and multiple responsive properties were obtained, which also possessed various functions. As a result of the transesterification reactions at elevated temperatures, the ENR-based vitrimers possess the ability to be reprocessed and self-healed, and the mechanical properties could be maintained even after three consecutive breaking/mold pressing cycles. Besides, the vitrimer is also responsive to near-infrared (NIR) light and pH with the introduction of ACAT, and we also find that ACAT can be used as a catalyst to accelerate the transesterification reaction. Moreover, it is demonstrated that the ENR-DA-ACAT vitrimer could also be used to construct the reconfigurable shape memory polymer; the shape fixing ratio and shape recovery ratio are both above 95% in the reconfiguration process, and the multistage shape memory performance can also be achieved by NIR irradiation, which will potentially lead to a wide application for ENR in the field of actuators.

11.
Macromol Rapid Commun ; 39(20): e1800138, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29722916

RESUMO

A versatile double-network (DN) hydrogel with two noncovalent crosslinked networks is synthesized by multiple hydrogen bonding (H-bonding) interactions. The DN hydrogels are synthesized via a heating-cooling photopolymerization process by adding all reactants of agar, N-acryloyl glycinamide (NAGA) and N-benzylacrylamide (NBAA) monomers, UV initiators to a single water pot. Poly(N-acryloyl glycinamide-co-N-benzyl acrylamide) (P(NAGA-co-NBAA)) with a triple amide in one side group is synthesized via UV-light polymerization between NAGA and NBAA, forming a strong intermolecular H-bonding network. Meanwhile, the intramolecular H-bonding network is formed between P(NAGA-co-NBAA) and agars. The sol-gel phase transition of agars at 86 °C generates the molecular entanglement network. Such a double network enables the hydrogel high self-healing efficiency (about 95%), good shape memory ability, and high mechanical strength (1.1 MPa). Additionally, the DN hydrogel is completely crosslinked by multiple hydrogen bonds (H-bonds) and the physical crosslinking of agar without extra potential toxic chemical crosslinker. The DN hydrogels find extensive applications in the biomedical materials due to their excellent biocompatibility.


Assuntos
Materiais Biocompatíveis/síntese química , Hidrogel de Polietilenoglicol-Dimetacrilato/síntese química , Polimerização/efeitos da radiação , Polímeros/síntese química , Acrilamida/química , Ágar/química , Materiais Biocompatíveis/química , Reagentes de Ligações Cruzadas/síntese química , Reagentes de Ligações Cruzadas/química , Glicina/análogos & derivados , Glicina/química , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Ligação de Hidrogênio/efeitos da radiação , Transição de Fase , Polímeros/química , Raios Ultravioleta , Água/química
12.
Macromol Rapid Commun ; 38(7)2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28199759

RESUMO

It is a significant but challenging task to simultaneously reinforce and functionalize diene rubbers. Inspired by "sacrificial bonds", the authors engineer sacrificial hydrogen bonds formed by pendent urazole groups in crosslinked solution-polymerized styrene butadiene rubber (SSBR) via triazolinedione click chemistry. This post-crosslinking modification reveals the effects of the sacrificial bonds based on a consistent covalent network. The "cage effect" of the pre-crosslinked network facilitates the heterogeneous distribution of urazole groups, leading to the formation of hydrogen-bonded multiplets. These multiplets further aggregate into clusters with vicinal trapped polymer segments that form microphase separation from the SSBR matrix with a low content of urazole groups. The clusters based on hydrogen bonds, serving as sacrificial bonds, promote energy dissipation, significantly improving the mechanical properties of the modified SSBR, and enable an additional wide transition temperature region above room temperature, which endows the modified SSBR with promising triple-shape memory behavior.


Assuntos
Butadienos/química , Butadienos/síntese química , Química Click , Elastômeros/química , Elastômeros/síntese química , Estirenos/química , Estirenos/síntese química , Triazóis/química , Biomimética , Ligação de Hidrogênio
13.
ACS Appl Mater Interfaces ; 9(7): 6482-6487, 2017 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-28116897

RESUMO

Adaptive mechanical behaviors in nature have inspired the development of synthetic adaptive composites, with those responsive to water particularly relevant for biomedical applications. Polymer nanocomposites containing cellulose nanocrystals (CNCs) are prime examples of water-responsive mechanically adaptive materials. Although CNCs are biobased, the matrixes of these composites are exclusively petroleum-based synthetic elastomers, in sharp contrast to their biological counterparts. In this work, we attempted to probe the possibility of using bioderived rubber(s) as the matrix to fabricate CNC-nanocomposite with water-responsive adaptive mechanical behaviors. Specifically, natural rubber (NR) and epoxidized natural rubber (ENR) were used as the composite matrixes. Our results show that the water-responsive sensitivity and reversibility of ENR composites is much more drastic than that of NR composites. This is attributed to the strong CNC-polymer interaction (hydrogen bonding) for ENR, which leads to better filler dispersion and the formation of an extra CNC-polymer network in addition to the CNC-CNC filler network present in the NR composite. The synergistic effect of the dual networks plays a key role in tuning the mechanical properties and water-responsive sensitivity for various potential biomedical applications. Our study further provides guidance to make use of renewable resources to produce high value added water-responsive nanocomposites.

14.
Polymers (Basel) ; 8(4)2016 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-30979208

RESUMO

The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated. A wide range of strain sensitivities and high repeatability are vital for different applications of CPCs. In this study, the relations of the conductive filler network and the strain-sensing behavior and electrical stability under fatigue cycles were studied systematically for the first time based on the conductive polymethylvinylsiloxane (PMVS) composites filled with both carbon nanotubes arrays (CNTAs) and carbon black (CB). It was proved that the composites could be fabricated with large strain-sensing capability and a wide range of strain sensitivities by controlling the volume ratio of CNTA/CB and their amounts. Additionally, the CNTA/CB/PMVS composite with 3 vol % content of fillers showed high sensitivity (GF is 10 at 60% strain), high repeatability (the relative standard deviation (RSD) of the max R/R0 value is 3.58%), and electrical stability under fatigue cycles (value range of R/R0 is 1.62 to 1.82) at the same time due to the synergistic effects of the dual conductive network of CNTAs and CB. This could not be achieved by relying on a single CNTA or CB conductive network. This study may provide guidance for the preparation of high performance CPCs for applications in strain sensors.

15.
Polymers (Basel) ; 8(4)2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30979235

RESUMO

We previously reported that the dispersed rubber microparticles in ethylene-propylene-diene monomer (EPDM)/polypropylene (PP) thermoplastic vulcanizates (TPVs) are actually agglomerates of rubber nanoparticles. In this study, based on this new understanding of the microstructure of TPV, we further revealed the microstructure-properties relationship of EPDM/PP TPV during dynamic vulcanization, especially the effect of the size of rubber nanoparticle agglomerates (dn), the thicknesses of PP ligaments (IDpoly) and the rubber network on the properties of EPDM/PP TPV. We were able to simultaneously obtain a high tensile strength, elongation at break, elastic modulus, and elasticity for the EPDM/PP TPV by the achievement of a smaller dn, a thinner IDpoly and a denser rubber network. Interestingly, the effect of dn and IDpoly on the elastic modulus of EPDM/PP TPV composed of rubber nanoparticle agglomerates is different from that of EPDM/PP TPVs composed of rubber microparticles reported previously. The deformation behavior of the TPVs during stretching was studied to understand the mechanism for the achievement of good mechanical properties. Interestingly, the rubber nanoparticle agglomerates are oriented along the tensile direction during stretching. The TPV samples with smaller and more numerous rubber nanoparticle agglomerates can slow down the development of voids and cracks more effectively, thus leading to increase in tensile strength and elongation at break of the EPDM/PP TPV.

16.
Polymers (Basel) ; 8(4)2016 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30979237

RESUMO

We present a density functional approach to quantitatively evaluate the microscopic conformations of polymer chains with consideration of the effects of chain stiffness, polymer concentration, and short chain molecules. For polystyrene (PS), poly(ethylene oxide) (PEO), and poly(methyl methacrylate) (PMMA) melts with low-polymerization degree, as chain length increases, they display different stretching ratios and show non-universal scaling exponents due to their different chain stiffnesses. In good solvent, increase of PS concentration induces the decline of gyration radius. For PS blends containing short (m1 = 1 - 100) and long (m = 100) chains, the expansion of long chains becomes unobvious once m 1 is larger than 40, which is also different to the scaling properties of ideal chain blends.

17.
J Phys Chem B ; 119(30): 9940-8, 2015 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-26135216

RESUMO

Silica nanoparticles dispersed in polystyrene, poly(methyl methacrylate), and poly(ethylene oxide) melts have been investigated using a density functional approach. The polymers are regarded as coarse-grained semiflexible chains, and the segment sizes are represented by their Kuhn lengths. The particle-particle and particle-polymer interactions are calculated with the Hamaker theory to reflect the relationship between particles and polymer melts. The effects of particle volume fraction and size on the particle dispersion have been quantitatively determined to evaluate their dispersion/aggregation behavior in these polymer melts. It is shown that theoretical predictions are generally in good agreement with the corresponding experimental results, providing the reasonable verification of particle dispersion/agglomeration and polymer depletion.

18.
Carbohydr Polym ; 130: 262-7, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26076625

RESUMO

To meet the growing demand of environmental protection and resource saving, it is imperative to explore bio-based elastomers as next-generation dielectric elastomers (DEs). In this study, we used a bio-based gelatin/glycerin (GG) elastomer as the DE matrix because GG exhibits high dielectric constant (ɛr). Cellulose nanocrystals (CNCs), extracted from natural cellulose fibers, were used to improve the mechanical strength of GG elastomer. The results showed that CNCs with a large number of hydroxyl groups disrupted the hydrogen bonds between gelatin molecules and formed new stronger hydrogen bonds with gelatin molecules. A good interfacial adhesion between CNCs and GG was formed, and thus a good dispersion of CNCs in GG matrix was obtained, leading to the improved mechanical strength of GG. More interestingly, the ɛr of GG elastomer was obviously increased by adding 5 wt% of CNCs, ascribed to the increase in the polarizability of gelatin chains caused by the disruption of hydrogen bonds of gelatin. As a result, a 230% increase in the actuated strain at low electric field of GG was obtained by adding 5 wt% of CNCs. Since CNCs, gelatin and glycerol are all bio-based, this study offers a new method to prepare high performance DE for its application in biological and medical fields.


Assuntos
Celulose/química , Elastômeros/química , Impedância Elétrica , Gelatina/química , Glicerol/química , Nanopartículas/química , Estresse Mecânico , Materiais Biomiméticos , Resistência à Tração
19.
ACS Appl Mater Interfaces ; 7(20): 10755-62, 2015 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-25938262

RESUMO

In this study, we obtained dielectric elastomer composites with controllable dielectric and actuated properties by using a biomimetic method. We used dopamine (DA) to simultaneously coat the graphene oxide (GO) and partially reduce GO by self-polymerization of DA on GO. The poly(dopamine) (PDA) coated GO (GO-PDA) was assembled around rubber latex particles by hydrogen bonding interaction between carboxyl groups of carboxylated nitrile rubber (XNBR) and imino groups or phenolic hydroxyl groups of GO-PDA during latex compounding, forming a segregated GO-PDA network at a low percolation threshold. The results showed that the introduction of PDA on GO prevented the restack of GO in the matrix. The dielectric and actuated properties of the composites depend on the thickness of PDA shell. The dielectric loss and the elastic modulus decrease, and the breakdown strength increases with increasing the thickness of PDA shell. The maximum actuated strain increases from 1.7% for GO/XNBR composite to 4.4% for GO-PDA/XNBR composites with the PDA thickness of about 5.4 nm. The actuated strain at a low electric field (2 kV/mm) obviously increases from 0.2% for pure XNBR to 2.3% for GO-PDA/XNBR composite with the PDA thickness of 1.1 nm, much higher than that of other DEs reported in previous studies. Thus, we successfully obtained dielectric composites with low dielectric loss and improved breakdown strength and actuated strain at a low electric field, facilitating the wide application of dielectric elastomers.


Assuntos
Materiais Biomiméticos/química , Elastômeros/química , Grafite/química , Indóis/química , Nanocompostos/química , Nanoconjugados/química , Polímeros/química , Materiais Revestidos Biocompatíveis/síntese química , Impedância Elétrica , Teste de Materiais , Nanoconjugados/ultraestrutura , Óxidos/química , Estresse Mecânico , Resistência à Tração
20.
Soft Matter ; 10(41): 8236-44, 2014 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-25183477

RESUMO

In this study, the effects of nanoparticle volume fraction, block stiffness, and diblock composition on the microstructure and electrical properties of composites are investigated using molecular dynamics simulation. It is shown that selective localization of conductive nanoparticles in a continuous block of diblock copolymer can dramatically reduce the percolation threshold. In the flexible-flexible copolymer systems with a relatively low particle loading, as the ratio of two blocks varies, one sees four kinds of phase structure: signal continuous, lamellar, co-continuous, and dispersed, corresponding to the order-disorder and continuity-dispersion transitions. In consideration of particle connectivity, the best electrical performance can be achieved with a special tri-continuous microstructure. While in the semi-flexible systems, the existence of rigid blocks can destroy the lamellar structure. If particles are located in the flexible block, a moderate stiffness of the rigid block can extensively enlarge the tri-continuous region, and high conductivity can be realized over a wide range of diblock compositions. If particles are located in the rigid block, however, high conductivity only emerges in a narrow composition range. In addition, the block should be prevented from becoming overstiff because this will cause direct particle aggregation.

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