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1.
Small ; : e2312135, 2024 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-38501794

RESUMO

Carbon fiber (CF) is a potential microwave absorption (MA) material due to the strong dielectric loss. Nevertheless, owing to the high conductivity, poor impedance matching of carbon-based  materials results in limited MA performance. How to solve this problem and achieve excellent MA performance remains a principal challenge. Herein, taking full advantage of CF and excellent impedance matching of bimetallic metal-organic frameworks (MOF) derivatives layer, an excellent microwave absorber based on micron-scale 1D CF and NiCoMOF (CF@NiCoMOF-800) is developed. After adjusting the oxygen vacancies of the bimetallic MOF, the resultant microwave absorber presented excellent MA properties including the minimum reflection loss (RLmin ) of -80.63 dB and wide effective absorption bandwidth (EAB) of 8.01 GHz when its mass percent is only 5 wt.% and the thickness is 2.59 mm. Simultaneously, the mechanical properties of the epoxy resin (EP)-based coating with this microwave absorber are effectively improved. The hardness (H), elastic modulus (E), bending strength, and compressive strength of CF@NiCoMOF-800/EP coating are 334 MPa, 5.56 GPa, 82.2 MPa, and 135.8 MPa, which is 38%, 15%, 106% and 53% higher than EP coating. This work provides a promising solution for carbon materials achieving excellent MA properties and mechanical properties.

2.
Small ; : e2402842, 2024 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-38923165

RESUMO

The nacre-inspired multi-nanolayer structure offers a unique combination of advanced mechanical properties, such as strength and crack tolerance, making them highly versatile for various applications. Nevertheless, a significant challenge lies in the current fabrication methods, which is difficult to create a scalable manufacturing process with precise control of hierarchical structure. In this work, a novel strategy is presented to regulate nacre-like multi-nanolayer films with the balance mechanical properties of stiffness and toughness. By utilizing a co-continuous phase structure and an extensional stress field, the hierarchical nanolayers is successfully constructed with tunable sizes using a scalable processing technique. This strategic modification allows the robust phase to function as nacre-like platelets, while the soft phase acts as a ductile connection layer, resulting in exceptional comprehensive properties. The nanolayer-structured films demonstrate excellent isotropic properties, including a tensile strength of 113.5 MPa in the machine direction and 106.3 MPa in a transverse direction. More interestingly, these films unprecedentedly exhibit a remarkable puncture resistance at the same time, up to 324.8 N mm-1, surpassing the performance of other biodegradable films. The scalable fabrication strategy holds significant promise in designing advanced bioinspired materials for diverse applications.

3.
Biomacromolecules ; 25(6): 3784-3794, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38743836

RESUMO

The effective regeneration of large bone defects via bone tissue engineering is challenging due to the difficulty in creating an osteogenic microenvironment. Inspired by the fibrillar architecture of the natural extracellular matrix, we developed a nanoscale bioengineering strategy to produce bone fibril-like composite scaffolds with enhanced osteogenic capability. To activate the surface for biofunctionalization, self-adaptive ridge-like nanolamellae were constructed on poly(ε-caprolactone) (PCL) electrospinning scaffolds via surface-directed epitaxial crystallization. This unique nanotopography with a markedly increased specific surface area offered abundant nucleation sites for Ca2+ recruitment, leading to a 5-fold greater deposition weight of hydroxyapatite than that of the pristine PCL scaffold under stimulated physiological conditions. Bone marrow mesenchymal stem cells (BMSCs) cultured on bone fibril-like scaffolds exhibited enhanced adhesion, proliferation, and osteogenic differentiation in vitro. In a rat calvarial defect model, the bone fibril-like scaffold significantly accelerated bone regeneration, as evidenced by micro-CT, histological histological and immunofluorescence staining. This work provides the way for recapitulating the osteogenic microenvironment in tissue-engineered scaffolds for bone repair.


Assuntos
Regeneração Óssea , Células-Tronco Mesenquimais , Osteogênese , Poliésteres , Engenharia Tecidual , Alicerces Teciduais , Animais , Alicerces Teciduais/química , Ratos , Regeneração Óssea/efeitos dos fármacos , Células-Tronco Mesenquimais/citologia , Osteogênese/efeitos dos fármacos , Osteogênese/fisiologia , Engenharia Tecidual/métodos , Poliésteres/química , Diferenciação Celular , Ratos Sprague-Dawley , Materiais Biomiméticos/química , Materiais Biomiméticos/farmacologia , Células Cultivadas , Proliferação de Células , Crânio/lesões , Crânio/patologia , Durapatita/química , Durapatita/farmacologia
4.
Biomacromolecules ; 25(4): 2438-2448, 2024 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-38502912

RESUMO

The treatment of infected wounds faces substantial challenges due to the high incidence and serious infection-related complications. Natural-based hydrogel dressings with favorable antibacterial properties and strong applicability are urgently needed. Herein, we developed a composite hydrogel by constructing multiple networks and loading ciprofloxacin for infected wound healing. The hydrogel was synthesized via a Schiff base reaction between carboxymethyl chitosan and oxidized sodium alginate, followed by the polymerization of the acrylamide monomer. The resultant hydrogel dressing possessed a good self-healing ability, considerable compression strength, and reliable compression fatigue resistance. In vitro assessment showed that the composite hydrogel effectively eliminated bacteria and exhibited an excellent biocompatibility. In a model of Staphylococcus aureus-infected full-thickness wounds, wound healing was significantly accelerated without scars through the composite hydrogel by reducing wound inflammation. Overall, this study opens up a new way for developing multifunctional hydrogel wound dressings to treat wound infections.


Assuntos
Quitosana , Hidrogéis , Hidrogéis/farmacologia , Cicatrização , Antibacterianos/farmacologia , Ciprofloxacina , Bandagens
5.
Biomacromolecules ; 24(7): 3127-3137, 2023 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-37276461

RESUMO

The relationship between the density of the entangled amorphous network and the ductility of oriented poly(l-lactide) (PLLA) films is explored based on the preferential hydrolysis of the amorphous regions in phosphate buffer solution (PBS). PLLA films with a balance of ductility and stiffness have been prepared by the "casting-annealing stretching" based on mechanical rejuvenation, and the structural evolution and mechanical properties at different hydrolysis durations have been identified. Various stages are found during the transition of ductility to brittleness for hydrolyzed PLLA films. First, the elongation at break for hydrolyzed PLLA films remains unchanged in the first stage of hydrolysis and then gradually decreases. Eventually, the films turn to be brittle in the third stage. The strain-hardening modulus (GR) of the hydrolyzed films is utilized to reflect the density of the entangled amorphous network, and a gradual decrease of GR with hydrolysis time indicates the decisive role of the amorphous entanglement network in the mechanical rejuvenation-induced ductility of PLLA. The quantitative relationship between the entangled amorphous network and the stress-induced ductility of PLLA films is revealed. The dependence of deformation behavior on entangled amorphous network density is closely correlated to activated primary structure during deformation. The intact chain network plays a crucial role in sufficiently activating the primary structure to yield and disentanglement during the subsequent necking. These findings could advance the understanding of the PLLA's ductility induced by mechanical rejuvenation and offer guidance for awakening the intrinsic toughness of PLLA.


Assuntos
Poliésteres , Poliésteres/química , Resistência à Tração , Hidrólise
6.
Small ; 18(2): e2104328, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738726

RESUMO

Cell polarization exists in a variety of tissues to regulate cell behaviors and functions. Space constraint (spatially limiting cell extension) and adhesion induction (guiding adhesome growth) are two main ways to induce cell polarization according to the microenvironment topographies. However, the mechanism of cell polarization induced by these two ways and the downstream effects on cell functions are yet to be understood. Here, space constraint and adhesion induction guiding cell polarization are achieved by substrate groove arrays in micro and nano size, respectively. Although the morphology of polarized cells is similar on both structures, the signaling pathways to induce the cell polarization and the downstream functions are distinctly different. The adhesion induction (nano-groove) leads to the formation of focal adhesions and activates the RhoA/ROCK pathway to enhance the myosin-based intracellular force, while the space constraint (micro-groove) only activates the formation of pseudopodia. The enhanced intracellular force caused by adhesion induction inhibits the chromatin condensation, which promotes the osteogenic differentiation of stem cells. This study presents an overview of cell polarization and mechanosensing at biointerface to aid in the design of novel biomaterials.


Assuntos
Sinais (Psicologia) , Osteogênese , Adesão Celular , Diferenciação Celular , Adesões Focais/metabolismo
7.
Biomacromolecules ; 23(9): 3990-4003, 2022 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-35960547

RESUMO

The hierarchical microstructure evolution of an emerging biobased odd-odd polyamide 5,13 (PA5,13) films under the thermo-mechanical field, stepping from hydrogen bond (H-bond) arrangement to the crystalline morphology, has been investigated systematically. It is found that the reorganization of H-bonds under the thermo-mechanical field plays a crucial role in the crystallization of PA5,13. Especially, it is revealed that the crystallization process under the thermo-mechanical field develops along the chain axis direction, while lamellar fragmentation occurs perpendicular to the chain axis. Consequently, a stable and well-organized H-bond arrangement and lengthened lamellae with significant orientation have been constructed. Laudably, an impressive tensile strength of about 500 MPa and modulus of about 4.7 GPa are thus achieved. The present study could provide important guidance for the industrial-scale manufacture of high-performance biobased odd-odd PAs with long polymethylene segment in the dicarboxylic unit combined with a large difference between the polymethylene segments in the dicarboxylic and diamine units.


Assuntos
Nylons , Ligação de Hidrogênio , Resistência à Tração
8.
Appl Opt ; 60(14): 4191-4196, 2021 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-33983174

RESUMO

By analyzing the process of time delay integration dynamic imaging, we establish a model of velocity mismatch. Based on this model, we analyze the influence of different factors on the dynamic imaging process, and a modulation transfer function (MTF) is used to evaluate imaging quality. According to the simulation, the velocity mismatch and scan stage are the main factors for image quality. The MTF of the image sensor decreases with the velocity mismatch, and the scan stage increases. In addition, an image with higher contrast can be obtained in a short integration time. However, a shorter integration time leads to insufficient sampling. Furthermore, we establish a dynamic MTF testing system, and evaluate the experiment at different imaging modes. Through data comparison, the experimental data are consistent with theoretical data.

9.
Biomacromolecules ; 20(7): 2754-2762, 2019 07 08.
Artigo em Inglês | MEDLINE | ID: mdl-31125205

RESUMO

Substantial adsorption of water vapor triggered by hydrogen-bonding interactions between water molecules and cellulose chains (or nanoplates) is hard to avoid in nanocomposite films, although the addition of nanoplates can improve the oxygen (or carbon dioxide) barrier property. In the present work, an effective strategy is raised to decline adsorption by weakening hydrogen-bonding interactions via chemical cross-linking by epichlorohydrin (ECH) without sacrificing the homogeneous dispersion of nanoplates. The generated microdomain structure of the chemical cross-linking reaction via ECH is explicitly revealed by micro-Raman imaging. Unambiguously, Raman maps of scanning elucidate the distribution and morphology of physical and chemical cross-linking domains quantitatively. The chemical cross-linking domains are nearly uniformly located in the matrix at a low degree of cross-linking, while the interconnected and assembled networks are formed at a high degree of cross-linking. ECH boosts the formation of chemical cross-linking microdomains, bringing out the terrific water vapor barrier property and alleviating the interfacial interactions in penetration, consequently magnifying the water contact angle and holding back the water vapor permeability. Our methodology confers an effective and convenient strategy to obtain remarkable water vapor-resistant cellulose-based films that meet the practical application in the packaging fields.


Assuntos
Celulose/química , Epicloroidrina/química , Nanocompostos/química , Água/química , Celulose/farmacologia , Reagentes de Ligações Cruzadas/química , Reagentes de Ligações Cruzadas/farmacologia , Epicloroidrina/farmacologia , Ligação de Hidrogênio/efeitos dos fármacos , Permeabilidade/efeitos dos fármacos , Análise Espectral Raman , Vapor
10.
Clin Orthop Relat Res ; 477(8): 1947-1955, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31107312

RESUMO

BACKGROUND: Synovial fluid components, especially lipids, can trigger oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) artificial joint components in vivo. The use of antioxidants such as vitamin E effectively diminishes the oxidative cascade by capturing free radicals and reducing the oxidation potential of UHMWPE implants. Using a thermo-oxidative aging method, we recently found that tea polyphenols can enhance the oxidation resistance of irradiated UHMWPE in comparison with commercial vitamin E. However, it is yet unknown whether tea polyphenols can reduce lipid-induced oxidation. QUESTIONS/PURPOSES: We explored whether tea polyphenol-stabilized UHMWPE would exhibit (1) lower squalene absorption; (2) stronger oxidation resistance; and (3) lower content of free radicals than vitamin E-stabilized UHMWPE under a physiologically-motivated in vitro accelerated-aging model. METHODS: Tea polyphenol (lipid-soluble epigallocatechin gallate [lsEGCG]) and vitamin E were blended with UHMWPE powders followed by compression molding and electron beam irradiation at 100 and 150 kGy. Small cubes (n = 3, 60 mg, 4 × 4 × 4 mm) cut from the blocks were doped in squalene at 60°, 80°, 100°, and 120° C for 2 hours. Gravimetric change of the cubes after squalene immersion was measured to assess absorption. Thin films (n = 3, ∼60 µm) were also microtomed from the blocks and were doped at 120° C for 24 hours. Oxidation induction time (n = 3, 5 mg of material from the cubes) and incipient oxidation temperature (n = 3, thin films) were obtained to determine the oxidation stability. Signal intensity of the free radicals, obtained by electron spin resonance spectroscopy, was used to qualitatively rank the antioxidant ability of vitamin E and lsEGCG. RESULTS: Squalene absorption was comparable between lsEGCG/UHMWPE and vitamin E/UHMWPE at a given temperature and radiation dose. The oxidation induction time of 100 kGy-irradiated UHMWPE was increased with lsEGCG compared with vitamin E except at 120° C. For example, the oxidation induction time value of 100 kGy-irradiated lsEGCG/UHMWPE immersed at 60 C was 25.3 minutes (24.2-27.8 minutes), which was 8.3 minutes longer than that of 100 kGy-irradiated vitamin E/UHMWPE which was 17.0 minutes (15.0-17.1 minutes) (p = 0.040). After squalene immersion at 120° C, the incipient oxidation temperature of 100 and 150 kGy irradiated lsEGCG/UHMWPE was 234° C (227-240° C) and 227° C (225-229° C), which was higher than vitamin E-stabilized counterparts with value of 217° C (214-229° C; p = 0.095) and 216° C (207-218° C; p = 0.040), respectively. The electron spin resonance signal of 150 kGy irradiated lsEGCG/UHMWPE was qualitatively weaker than that of 150 kGy irradiated vitamin E/UHMWPE. CONCLUSIONS: lsEGCG-stabilized UHMWPE demonstrated higher oxidation resistance than vitamin E-stabilized UHMWPE after squalene immersion, likely because lsEGCG donates more protons to eliminate macroradicals than vitamin E. CLINICAL RELEVANCE: Our in vitro findings provide support that lsEGCG may be effective in protecting against oxidation that may be associated with synovial fluid-associated oxidation of highly crosslinked UHMWPE joint replacement components.


Assuntos
Antioxidantes/química , Catequina/análogos & derivados , Prótese Articular , Extratos Vegetais/química , Polietilenos/química , Vitamina E/química , Antioxidantes/isolamento & purificação , Camellia sinensis/química , Catequina/química , Catequina/isolamento & purificação , Radicais Livres/química , Oxirredução , Extratos Vegetais/isolamento & purificação , Polietilenos/efeitos da radiação , Falha de Prótese , Esqualeno/química , Fatores de Tempo
11.
Mol Ther ; 25(5): 1222-1233, 2017 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-28342639

RESUMO

Accumulating evidence has shown the protective role of CD8+ T cells in vaccine-induced immunity against Mycobacterium tuberculosis (Mtb) despite controversy over their role in natural immunity. However, the current vaccine BCG is unable to induce sufficient CD8+ T cell responses, especially in the lung. Sendai virus, a respiratory RNA virus, is here engineered firstly as a novel recombinant anti-TB vaccine (SeV85AB) that encodes Mtb immuno-dominant antigens, Ag85A and Ag85B. A single mucosal vaccination elicited potent antigen-specific T cell responses and a degree of protection against Mtb challenge similar to the effect of BCG in mice. Depletion of CD8+ T cells abrogated the protective immunity afforded by SeV85AB vaccination. Interestingly, only SeV85AB vaccination induced high levels of lung-resident memory CD8+ T (TRM) cells, and this led to a rapid and strong recall of antigen-specific CD8+ T cell responses against Mtb challenge infection. Furthermore, when used in a BCG prime-SeV85AB boost strategy, SeV85AB vaccine significantly enhanced protection above that seen after BCG vaccination alone. Our findings suggest that CD8+ TRM cells that arise in lungs responding to this mucosal vaccination might help to protect against TB, and SeV85AB holds notable promise to improve BCG's protective efficacy in a prime-boost immunization regimen.


Assuntos
Vacina BCG/administração & dosagem , Linfócitos T CD8-Positivos/imunologia , Imunização Secundária/métodos , Vírus Sendai/genética , Tuberculose Pulmonar/prevenção & controle , Vacinação/métodos , Aciltransferases/genética , Aciltransferases/imunologia , Animais , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Carga Bacteriana , Proteínas de Bactérias/genética , Proteínas de Bactérias/imunologia , Linfócitos T CD8-Positivos/microbiologia , Modelos Animais de Doenças , Feminino , Expressão Gênica , Engenharia Genética , Imunidade nas Mucosas , Imunogenicidade da Vacina , Memória Imunológica , Pulmão/imunologia , Pulmão/microbiologia , Depleção Linfocítica , Camundongos , Camundongos Endogâmicos BALB C , Mycobacterium tuberculosis/imunologia , Mycobacterium tuberculosis/patogenicidade , Mucosa Respiratória/imunologia , Mucosa Respiratória/microbiologia , Vírus Sendai/imunologia , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/microbiologia
12.
Macromol Rapid Commun ; 38(23)2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28960607

RESUMO

Flow-induced oriented crystals have attracted considerable attention because they significantly increase stiffness and strength of polymer products. Naturally, understanding the necessary condition of forming oriented crystals is of importance for both industry and polymer physics. Following the concept of specific work of flow proposed by Mykhaylyk and co-workers, the expression of the specific work of flow, w (T,P) , was carefully summarized and verified that when w (T,P) is above a critical specific work of flow, w c(T,P) = (1.7 ± 0.7) × 107 J m-3 , oriented crystals in isotactic polypropylene can be induced by flow at pressures (50, 100, and 150 MPa) and at a undercooling of 65 K. The influences of pressure on w c(T,P) stem from two facets: one is the influence on the melt viscosity (the Barus law), and the other one is the influence on the equilibrium melting temperature (the Clapeyron equation). The current study can guide real processing to fabricate high-performance polymer products with oriented crystals.


Assuntos
Polímeros/química , Polipropilenos/química , Cristalização , Pressão , Temperatura
13.
Macromol Rapid Commun ; 37(9): 745-51, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26987565

RESUMO

The realization of hierarchical shish-kebab structures for stereocomplex poly(lactic acid) (PLA) is achieved by the application of a shear flow (100 s(-1) for 1 s) mimicking what can be expected during polymer processing. Compared to the normal shearing scenarios, this transient and strong shear flow enables the creation of dense shish precursors in time- and energy-saving manner. The distribution of crystal form associated with the hierarchical structure is revealed by 2D Fourier transform infrared spectroscopy imaging, creating a unique visualization for both spatial resolution and polymorphism identification. Interestingly, in the shear stereocomplex chains are preferentially extended and crystallized as stable central cores with weak temperature dependence, whereas the development of lateral kebabs is defined by the distinct relation to the crystallization temperature. Below the melting point of homocrystals, both homo and stereocomplex crystallization are engaged in lamellar packing. Above that, exclusive stereocomplex crystals are organized into ordered lamellae. Combining the direct observations at multiscale, the ordered alignment of stereocomplex chains is recognized as the molecular origin of fibrillar extended chain bundles that constitute the central row-nuclei. The proposed hypothesis affords elucidation of shish-kebab formation and unique polymorphism in sheared stereocomplex PLA, which generates opportunities for engendering hierarchically structured PLA with improved performance.


Assuntos
Poliésteres/química , Resistência ao Cisalhamento , Espectroscopia de Infravermelho com Transformada de Fourier
14.
Macromol Rapid Commun ; 37(9): 808, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27135415

RESUMO

Back Cover: The shish-kebab superstructure of poly(lactic acid) stereocomplex was developed in a transient and strong shear flow. The shear-aligned stereocomplex chains were preferentially assembled into the central shish, while the crystal form of the lateral kebabs showed strong dependency on the crystallization temperature. Further details can be found in the article by L. Xie, H. Xu, Z.-M. Li, and M. Hakkarainen* on page 745.

15.
Biomacromolecules ; 15(5): 1676-86, 2014 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-24650138

RESUMO

A local shear flow field was feasibly generated by pulling the ramie fiber in single fiber reinforced poly(lactic acid) (PLA) composites. This was featured by an ultrahigh shear gradient with a maximum shear rate up to 1500 s(-1), a level comparable to that frequently occurring during the practical polymer processing. To distinguish shear-induced self-nucleation and ramie fiber-induced heterogeneous nucleation, the shear history was classified by pulling the fiber for 5 s (pulled sample) and pulling out the fiber during 10 s (pulled-out sample), while the static fiber-induced crystallization was carried out as the counterpart. As a result of the ultrahigh shear gradient, the combination of primary shear-induced nucleation in the central region and secondary nucleation in the outer layer assembled the unique hierarchical superstructures. By comparing the architectural configurations of interphases formed in the static, pulled, and pulled-out samples, it was shown that the hierarchical cylindrites underwent the process of self-nucleation driven by the applied shear flow, very different from the formation of fiber-induced transcrystallinity (TC) triggered by the heterogeneous nucleating sites at the static fiber surface. The twisting of transcrystallized lamellae may take place due to the spatial hindrance induced by the incredibly dense nuclei under the intense shearing flow, as observed in the synchrotron X-ray diffraction patterns. The influence of chain characteristics on the crystalline morphology was further explored by adding a small amount of poly(ethylene glycol) (PEG) to enhance the molecular mobility of PLA. It was of interest to find that the existence of PEG not only facilitated the growth rates of TC and cylindrites but also improved the preferential orientation of PLA chains and thus expanded the ordered regions. We unearthed lamellar units that were composed of rich fibrillar extended chain crystals (diameter of 50-80 nm). These results are of importance to shed light on tailoring crystalline morphology for natural fibers reinforced green composite materials. Of immense practical significance, too, is the crystalline evolution that has been tracked in the simple model penetrated with an ultrahigh shear gradient, which researchers have so far been unable to replicate during the practical melt processing, such as extrusion and injection molding.


Assuntos
Ácido Láctico/química , Polímeros/química , Ácido Láctico/síntese química , Estrutura Molecular , Tamanho da Partícula , Poliésteres , Polietilenoglicóis/química , Polímeros/síntese química , Propriedades de Superfície
16.
Biomacromolecules ; 15(11): 4054-64, 2014 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-25245861

RESUMO

The notion of toughening poly(lactic acid) (PLA) by adding flexible biopolymers has generated enormous interest but has yielded few desirable advances, mainly blocked by the sacrifice of strength and stiffness due to uncontrollable phase morphology and poor interfacial interactions. Here the phase control methodology, that is, intense extrusion compounding followed by "slit die extrusion-hot stretching-quenching" technique, was proposed to construct well-aligned, stiff poly(butylene succinate) (PBS) nanofibrils in the PLA matrix for the first time. We show that generating nanosized discrete droplets of PBS phase during extrusion compounding is key to enable the development of in situ nanofibrillar PBS assisted by the shearing/stretching field. The size of PBS nanofibrils strongly dependent on the PBS content, showing an increased average diameter from 83 to 116 and 236 nm for the composites containing 10, 20, and 40 wt % nanofibrils, respectively. More importantly, hybrid shish-kebab superstructure anchoring ordered PLA kebabs were induced by the PBS nanofibrils serving as the central shish, conferring the creation of tenacious interfacial crystalline ligaments. The exceptional combination of strength, modulus, and ductility for the composites loaded 40 wt % PBS nanofibrils were demonstrated, outperforming pure PLA with the increments of 31, 51, and 72% in strength, modulus, and elongation at break (56.4 MPa, 1702 MPa, and 92.4%), respectively. The high strength, modulus, and ductility are unprecedented for PLA and are in great potential need for packaging applications.


Assuntos
Butileno Glicóis/química , Química Verde/métodos , Ácido Láctico/química , Nanofibras/química , Polímeros/química , Teste de Materiais/métodos , Poliésteres , Resistência à Tração , Substâncias Viscoelásticas/síntese química
17.
Nanotechnology ; 25(14): 145705, 2014 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-24633439

RESUMO

An in situ thermally reduced graphene/polyethylene conductive composite with a segregated structure was fabricated, which achieved a high electromagnetic interference shielding effectiveness of up to 28.3-32.4 dB at an ultralow graphene loading of 0.660 vol.%. Our work suggests a new way of effectively using graphene.

18.
Carbohydr Polym ; 337: 122088, 2024 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-38710544

RESUMO

The construction of the preferred orientation structure by stretching is an efficient strategy to fabricate high-performance cellulose film and it is still an open issue whether crystalline structure or amorphous molecular chain is the key factor in determining the enhanced mechanical performance. Herein, uniaxial stretching with constant width followed by drying in a stretching state was carried out to cellulose hydrogels with physical and chemical double cross-linking networks, achieving high-performance regenerated cellulose films (RCFs) with an impressive tensile strength of 154.5 MPa and an elastic modulus of 5.4 GPa. The hierarchical structure of RCFs during uniaxial stretching and drying was systematically characterized from micro- to nanoscale, including microscopic morphology, crystalline structure as well as relaxation behavior at a molecular level. The two-dimensional correlation spectra of dynamic mechanical analysis and Havriliak-Negami fitting results verified that the enhanced mechanical properties of RCFs were mainly attributed to the stretch-induced tight packing and restricted relaxation of amorphous molecular chains. The new insight concerning the contribution of molecular chains in the amorphous region to the enhancement of mechanical performance for RCFs is expected to provide valuable guidance for designing and fabricating high-performance eco-friendly cellulose-based films.

19.
Adv Healthc Mater ; 13(17): e2304178, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38490686

RESUMO

Structural engineering is an appealing means to modulate osteogenesis without the intervention of exogenous cells or therapeutic agents. In this work, a novel 3D scaffold with anisotropic micropores and nanotopographical patterns is developed. Scaffolds with oriented pores are fabricated via the selective extraction of water-soluble polyethylene oxide from its poly(ε-caprolactone) co-continuous mixture and uniaxial stretching. The plate apatite-like lamellae are subsequently hatched on the pore walls through surface-induced epitaxial crystallization. Such a unique geometric architecture yields a synergistic effect on the osteogenic capability. The prepared scaffold leads to a 19.2% and 128.0% increase in the alkaline phosphatase activity of rat bone mesenchymal stem cells compared to that of the scaffolds with only oriented pores and only nanotopographical patterns, respectively. It also induces the greatest upregulation of osteogenic-related gene expression in vitro. The cranial defect repair results demonstrate that the prepared scaffold effectively promotes new bone regeneration, as indicated by a 350% increase in collagen I expression in vivo compared to the isotropic porous scaffold without surface nanotopology after implantation for 14 weeks. Overall, this work provides geometric motifs for the transduction of biophysical cues in 3D porous scaffolds, which is a promising option for tissue engineering applications.


Assuntos
Regeneração Óssea , Células-Tronco Mesenquimais , Osteogênese , Alicerces Teciduais , Animais , Alicerces Teciduais/química , Regeneração Óssea/efeitos dos fármacos , Ratos , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/metabolismo , Porosidade , Osteogênese/efeitos dos fármacos , Anisotropia , Engenharia Tecidual/métodos , Poliésteres/química , Ratos Sprague-Dawley , Materiais Biomiméticos/química , Materiais Biomiméticos/farmacologia , Masculino , Fosfatase Alcalina/metabolismo , Crânio
20.
Int J Biol Macromol ; 261(Pt 2): 129829, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38296134

RESUMO

Three-dimensional interpenetrating and hierarchically porous carbon material is an efficient catalyst support in water remediation and it is still a daunting challenge to establish the relationship between hierarchically porous structure and catalytic degradation performance. Herein, a highly porous silica (SiO2)/cellulose-based carbon aerogel with iron-based catalyst (FexOy) was fabricated by in-situ synthesis, freeze-drying and pyrolysis, where the addition of SiO2 induced the hierarchically porous morphology and three-dimensional interpenetrating sheet-like network with nitrogen doping. The destruction of cellulose crystalline structure by SiO2 and the iron-catalyzed breakdown of glycosidic bonds synergistically facilitated the formation of electron-rich graphite-like carbon skeleton. The unique microstructure is confirmed to be favorable for the diffusion of reactants and electron transport during catalytic process, thus boosting the catalytic degradation performance of carbon aerogels. As a result, the catalytic degradation efficiency of tetracycline under light irradiation by adding only 5 mg of FexOy/SiO2 cellulose carbon aerogels was as high as 90 % within 60 min, demonstrating the synergistic effect of photocatalysis and Fenton reaction. This ingenious structure design provides new insight into the relationship between hierarchically porous structure of carbon aerogels and their catalytic degradation performance, and opens a new avenue to develop cellulose-based carbon aerogel catalysts with efficient catalytic performance.


Assuntos
Carbono , Compostos Heterocíclicos , Carbono/química , Ferro/química , Dióxido de Silício , Celulose/química , Porosidade , Tetraciclina/química , Antibacterianos , Catálise
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