Tailoring Organic-Organic Poly(vinylpyrrolidone) Microparticles and Fibers with Multiwalled Carbon Nanotubes for Reinforced Composites

Polymeric-based microparticles and fibers are tailorable for a wide range of common industrial and biomedical applications, while multiwalled carbon nanotubes (MWCNTs) are among the most useful macromolecules based on their outstanding electronic, mechanical, and optical properties at the nanoscale. If one combines these nanostructures with various polymeric precursors, their range of potential applications becomes even greater. One of the simplest and most affordable methods for fabricating micro- and nanostructures is electrospinning. Herein we demonstrate how MWCNTs may be used to produce tailor-made organic-organic poly(vinylpyrrolidone) (PVP) microparticles and fibers via electrospinning by studying their structural, vibrational, rheological, and mechanical properties' dependence on their solvent (ethanol (EtOH) or dimethylformamide (DMF)) and resulting morphology. Specifically, we find clear differences in morphologies from perfectly spherical and isolated microparticles to fibers mats, or a combination of fibers with entangled beads, with solvent type and concentration. On the basis of our findings, we propose that the mechanism governing the shape and size of the particles is a competition between the solvent's surface tension, dielectric constant, and viscoelastic properties. We show, based on both our experimental results and density functional theory (DFT) calculations, that OH functionalization of the MWCNTs is essential for achieving high PVP coverages and promoting the stability of the resulting PVP/MWCNT nanocomposite. Finally, by fabricating PVP/MWCNT fiber mats, we demonstrate that low concentrations (0.01-0.1 wt %) of MWCNTs led to a qualitative improvement (â250%) in the resulting mechanical properties, i.e., a reinforced composite. These results show how by controlling the solvent's dielectric constant, surface tension, and polymer concentration, one may produce tailor-made polymeric nanomaterials in combination with other organic/inorganic nanoparticles, i.e., silver, gold, or carbon allotropes, for next-generation applications

Improving glass-fiber epoxy composites via interlayer toughening with polyacrylonitrile/multiwalled carbon nanotubes electrospun fibers

The development of innovative engineered epoxy composites aiming to manufacture cost-efficient materials with reduced weight and enhanced physical properties remains as a current industrial challenge. In this work we report an original procedure for manufacturing glass-fiber epoxy reinforced nanocomposites (GFECs) by employing electrospun fiber-mats as a reinforcing phase. These fibers have been produced from polyacrylonitrile and multiwalled carbon nanotubes solutions. Optimal protocols are designed by combining Taguchi method with the morphological, structural and mechanical properties obtained by scanning electron microscopy, profilometry and tensile tests. It is demonstrated that GFECs fabricated using GF800 glass fiber show an improvement/enhancement of the mechanical properties with a fracture strain up to 500¿MPa (around 20% higher than the non-reinforced epoxy composite counterpart). It is also shown that GFECs fabricated using GF3M glass fiber exhibited a reduction of the roughness up to 56%, which corresponds with a roughness improvement from N8 to N7 following the guidelines provided by the ISO 1302. These results suggest that this type of nanocomposites would be suitable to be used in the aeronautics and automotive industries.This work was financially supported by the “Convocatoria de Ayudas a la Realización de Proyectos de Grupos de Investigación 2020-2021” of the Universidad Católica de Murcia (UCAM), Spain, Reference: PMFI-12/21. Pavel Ryzhakov, Jordi Pons-Prats, and Christian Narváez- Muñoz would also like to acknowledge the support of the Ministerio de Ciencia, Innovación y Universidades of Spain via the “Severo Ochoa Programme” for Centres of Excellence in R&D (reference: CEX2018-000797-S) given to the International Centre for Numerical Methods in Engineering (CIMNE). The work of Christian Narváez- Muñoz was financially supported by the “Severo Ochoa PhD Scholarship” Reference: PRE2020-096632. Pavel Ryzhakov and Jordi Pons-Prats are Serra Hunter fellows.Peer ReviewedPostprint (author's final draft

Biomedical Science to Tackle the COVID-19 Pandemic: Current Status and Future Perspectives

The coronavirus infectious disease (COVID-19) pandemic emerged at the end of 2019, and was caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which has resulted in an unprecedented health and economic crisis worldwide. One key aspect, compared to other recent pandemics, is the level of urgency, which has started a race for finding adequate answers. Solutions for efficient prevention approaches, rapid, reliable, and high throughput diagnostics, monitoring, and safe therapies are needed. Research across the world has been directed to fight against COVID-19. Biomedical science has been presented as a possible area for combating the SARS-CoV-2 virus due to the unique challenges raised by the pandemic, as reported by epidemiologists, immunologists, and medical doctors, including COVID-19’s survival, symptoms, protein surface composition, and infection mechanisms. While the current knowledge about the SARS-CoV-2 virus is still limited, various (old and new) biomedical approaches have been developed and tested. Here, we review the current status and future perspectives of biomedical science in the context of COVID-19, including nanotechnology, prevention through vaccine engineering, diagnostic, monitoring, and therapy. This review is aimed at discussing the current impact of biomedical science in healthcare for the management of COVID-19, as well as some challenges to be addressed

Orientational order of single-wall carbon nanotubes in stretch-aligned photoluminescent composite films

Aqueous suspensions of single-wall carbon nanotubes (SWNT) are mixed with solutions of polyvinylalcohol (PVA) and dried to prepare free standing SWNT/PVA composite films (~100 μm thick). For nanotube concentrations up to 1wt %, the composites are homogeneous and the nanotubes are well dispersed both at mesoscopic scales and down to the individual scale as revealed by microscopic pictures and strong photoluminescence (PL) signals, repectively. We study the alignment of SWNT in the composites using polarized Raman and PL spectroscopies. Alignment can be continuously adjusted by hot-stretching the PVA composites. We propose a simple relation to measure the order parameter, based on the assumption that only one single component of the Raman polarizability tensor is non-zero. This assumption is validated experimentally by the observation of similar profiles for spectra measured in different polarization configurations. We modelize the orientation of the nanotubes under uniaxial stretching by a simple affine model assuming deformation at constant volume. For high nanotube concentrations, we discuss the effect of absorption on the Raman/PL results and show how it can be taken into account to measure the order parameter accurately

Orientational order of single-wall carbon nanotubes in stretch-aligned photoluminescent composite films

International audienceWe study the alignment of single-wall carbon nanotubes in polyvinylalcohol composites using polarized Raman and photoluminescence spectroscopies. Nanotubes are well dispersed down to the individual scale in the composites as revealed by the strong photoluminescence signal. Alignment can be continuously adjusted by hot stretching the composites. We propose a simple relation to measure the order parameter based on the assumption that only one single component of the Raman polarizability tensor is nonzero. The similar profiles of spectra measured in different polarization configurations validate this assumption. The orientation of the nanotubes under uniaxial stretching is well modelized by a simple affine model assuming deformation at constant volume

Estudio de sistemas anisotrópicos basados en nanotubos de carbono (propriedades estructurales, orientacionales y ópticas)

Les nanotubes de carbone présentent des propriétés physiques (mécaniques, thermiques, électroniques, optiques ) exceptionnelles à l'échelle du nanotube individuel. L'optimisation de ces propriétés dans des matériaux composites à l'échelle macroscopique nécessite de bien maîtriser la dispersion et l'orientation des nanotubes. Ce travail de thèse est consacré à l'élaboration de différents types de composites à base de nanotubes de carbone monofeuillets et à l'étude de leurs propriétés optiques, en particulier de photoluminescence. L'étude de l'ordre orientationnel des nanotubes dans les composites est réalisée par microscopie optique polarisée et spectroscopies d'absorption, Raman et de photoluminescence. Tous les matériaux étudiés sont préparés à partir de suspensions aqueuses de nanotubes individuels stabilisés par des surfactants (SDS ou ADN dénaturé). Des gels composites silice/nanotubes préparés par voie sol-gel présentent une forte photoluminescence mais cette propriété est perdue dans les xérogels et aérogels obtenus par séchage des gels. Des phases nématiques lyotropes sont préparées en concentrant des suspensions aqueuses de nanotubes/ADN puis orientées en cellules minces par cisaillement. Des films minces anisotropes sont obtenus par séchage des suspensions. Le paramètre d'ordre mesuré sur ce type d'échantillon est faible (autour de 0,2) mais le contrôle du facteur d'aspect des nanotubes laisse envisager une forte amélioration. Par ailleurs, des nanotubes sont dispersés dans une phase lyotrope nématique discotique de cristal liquide (cromolyn). Sous champ magnétique, le nématique s'oriente et induit une bonne orientation des nanotubes parallèlement au directeur (paramètre d'ordre 0,64). Enfin, des films composites PVA/nanotubes sont préparés et étirés à chaud. Le paramètre d'ordre varie en fonction de l'étirement et atteint 0,8 pour un étirement de 400%. Cette série d'échantillons modèles permet de valider les hypothèses utilisées pour mesurer le paramètre d'ordre par spectroscopies Raman et photoluminescence. Un modèle géométrique simple rend bien compte de l'orientation sous étirement des nanotubes dans les composites. Les propriétés de photoluminescence (énergies d'absorption et d'émission, intensité) varient sensiblement avec l'environnement physico-chimique des nanotubes.Carbon nanotubes present exceptional physical (mechanical, thermal, elctronic, optical ) properties at the individual scale. In order to optimize these properties in composite materials at the macroscopic scale, a good control of the dispersion and anisotropy of the nanotubes is required. This PhD work is devoted to the elaboration of various singlewall carbon nanotubes-based composites and to the study of their optical properties, especially photoluminescence. The study of the orientational order of nanotubes in the composites is achieved by polarized optical microscopy as well as absorption, Raman and photoluminescence spectroscopies. All studied materials are prepared from aqueous suspensions of individual nanotubes stabilized by surfactants (SDS or denaturated DNA). Silica/nanotube composites prepared by the sol-gel process display a strong photoluminescence signal but this property is lost in the xerogels and aerogels obtained by drying of the gels. Lyotropic nematic phases are prepared by concentrating nanotubes/DNA aqueous supensions and orientated in thin cells by shearing. Thin anisotropic films are obtained from wetting aligned suspensions. The order parameter measured on this kind of sample is weak (about 0.2) but significant improvement is expected by the control of the nanotubes aspect ratio. On the other hand, nanotubes are dispersed in a chomonic liquid crystal, i.e. a discotic nematic lyotropic phase (cromolyn). The nematic orientates under magnetic field and induces a good orientation of the nanotubes parallel to the director (order parameter about 0.64). Finally, PVA/nanotubes composite films are prepared and hot-stretched. The order parameter varies as a function of stretching and increases up to 0.8 for a stretching of 400%. This series of model samples allows us to validate the hypothesis used to measure the order parameter from Raman and photoluminescence measurements. A simple geometrical model describes well the stretch-induced orientation in the composites. The photoluminescence properties (absorption and emission energies, intensity) are very sensitive to the chemical/physical environment of the nanotubes.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Influence of sonication time on dispersion and photoluminescence intensity of SWNT aqueous dispersions

Processing routes and characterization methods commonly used in carbon nanotubes research require agood dispersion of nanotubes in liquid media. In particular, single walled carbon nanotubes (SWNT) mustbe dispersed, preferably as individuals in order to tap their full potential in optical applications [1]. Onesensitive probe of dispersion is photoluminescence (PL), since it is quenched as long as semiconductingSWNT are bundled with metallic ones. However, the detailed interpretation of the mechanismsresponsible for PL and the relation between PL intensity and dispersion state are still a matter ofcontroversy [2].In this work, we present new insights on the near infrared photoluminescence of aqueous suspensions ofSWNT stabilized by bile salts surfactants. In one hand, the dispersion of the nanotubes is probed byabsorption spectroscopy, where the absorption coefficient shows high sensitivity to nanotube exfoliation.On the other hand, we revisit the interpretation of the NIR-PL spectra, and we discuss the differentphysical mechanisms responsible of the PL, i.e. Direct Excitonic Transitions (DET), Exciton-PhononCoupling (EPC), and Exciton Energy Transfer (EET) between nanotubes [3-7]. Finally, we discuss thekinetics of PL as a function of sonication time and debundling/exfoliation of SWNT (Figure 1).References [1] S. M. Bachilo, et al. Science, 298 (2002). pp 2361-2366.[2] V.C Moore, et al. Nano letters, 3 (2003). pp 1379-1382.[3] T. Ando, J. Phys. Soc. Jpn, 66(4) (1997). pp. 1066-1073.[4] J. Maultzsch, et al. PRB, 72(24) (2005). pp. 241402.[5] F. Wang, et al. Science, 308(5723) 2005. pp. 838-841.[6] S. Chou, et al. PRL, 94(12) (2005), pp. 127402.[7] P. Tan, et al. PRL, 99(13) (2007) pp. 137402.NanoTubes And Liquid crystal

Natural vs Synthetic Polymers: How Do They Communicate with Cells for Skin Regeneration—A Review

Modern research has evolved several approaches toward skin regeneration and one of the novel concerns is the use of polymer-based systems due to their excellent beneficial properties to the skin. Several polymers, such as cellulose, hyaluronan, alginate, chitosan, collagen, fibrin and fibroin, have been tested and have proven the benefits for skin regeneration, and most of them are derived from either polysaccharide- or protein-based materials. In order to understand the mode of action, several researchers investigated the cell–matrix interaction and possible signaling mechanism in skin regeneration. Not only the signaling mechanism but also the mode of cell communication determines the application of polysaccharide- and protein-based polymers in practice. Based on the above significance, this review disclosed the recent findings to compile a possible method of communication between cells and polymers derived from polysaccharide-based (such as cellulose, hyaluronan, chitosan, alginate, agar, and xanthan gum) and protein-based (such as collagen, gelatin, fibrin, and silk fibroin) materials along with other polymers, such as poly(vinyl alcohol), polyglycolide or poly(glycolic acid), or poly(lactic acid) in skin regeneration. Accordingly, this review addresses the fundamental concept of cell–matrix communication, which helps us to understand the basis of the polymer’s functions in the biomedical field

Ordering, Instabilities and Textures in Graphene BasedLiquid Crystalline phases

International audienceTo date, aqueous stable graphene flakes solutionscan be obtained by simple REDOX reactions.1–5 Most of the current applications regardinggraphene require ordered nanostructuredcomposites materials. Liquid crystal phases orderingrepresent an opportunity to arrange theminto macroscopic assemblies with long-rangeordering. 1,2 Preparing organized materials andthin films from these dispersions then requires agood control of the liquid crystal ordering duringthe deposition and the drying of the films. As amatter of fact, it turns out that graphene flakeseasily align at high shear.3,4 On the other hand,Graphene Flakes Liquid Crystals (GFLC) exhibita very interesting behaviour at low shear or undersmall displacements, thin films often showspeculiar patterns (such as the periodic texturesshown in Fig.72-72). We have shown how tocreate and stabilize large-sized periodic texturesin GFLC. The patterns have been characterizedunder optical and electronic microscopies. Theirstability can be explained by the competition betweenthe anchoring field of the substrate andthe presence of a yield stress resulting fromthe peculiar elastic and rheological properties ofthe GFLC. Our findings also clarify why longstandinghypotheses on the presence of exoticphases1 at large concentrations are present inthe literature.References[1] Zakri, C.; Blanc, C.; Grelet, E.; Zamora-Ledezma, C.; Puech, N.; Anglaret, E.; Poulin, P. Philosophical Transactions of theRoyal Society A: Mathematical, Physical and Engineering Sciences 2013, 371, 20120499..[2] Zamora-Ledezma, C.; Puech, N.; Zakri, C.; Grelet, E.; Moulton, S. E.; Wallace, G. G.; Gambhir, S.; Blanc, C.; Anglaret, E.;Poulin, P. The journal of physical chemistry letters 2012, 3, 2425–2430..[3] Poulin, P.; Jalili, R.; Neri, W.; Nallet, F.; Divoux, T.; Colin, A.; Aboutalebi, S. H.; Wallace, G.; Zakri, C. Proceedings of theNational Academy of Sciences 2016, 113, 11088–11093..[4] Zamora-Ledezma, C.; Jeridi, H.; Anglaret, E.; Blanc, C. Orientations and periodic textures in graphene liquid crystals. 27thInternational Liquid Crystal Conference (ILCC2018). 2018..[5] Xu, Z.; Gao, C. Nature communications 2011, 2, 571

Nematic liquid crystals of graphene flakes

Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneouslyaligned anisotropic particles [1,2]. In this way, the organization of graphene flakes in liquid crystals provides new methodologies for the still challenging structural characterization of such materials. In this work, we will present a review of our recent results in the preparation and characterization of lyotropic LC made from concentrated aqueous suspensions based graphene oxide (GO) and/or reduced graphene oxide (RGO), and we will show some of ours preliminary approaches to achieve large and well-ordered domains of lyotropic liquid crystals. According with literature, for graphene, it is known that GO flakes easily disperse in water and spontaneously form liquid crystals at high concentrations. However, most of their electronic functionalities are lost during the oxidation treatments. RGO is of greater interest since a large part of functionalities are recovered but chemical reduction of GO in water generally results in the aggregation of the flakes. We recently showed how to obtain water-based RGO liquid crystals stabilized by surfactant molecules [3]. Structural and thermodynamic characterizations provide statistical information on the dimensions of the graphene flakes, which are found to be comparable with those of neat graphene oxide flakes. We have started to combined these new liquid crystals with nanoparticles, these graphene-based LC/Nanoparticles composites being useful to design coatings and functional materials.References[1] Yuan J.; Luna A.; Neri W.; Zakri C.; Schilling T.; Colin A.; Poulin, P. Graphene liquid crystal retardedpercolation for new high-k materials. Nat. Commun. 6:8700 (2015) doi: 10.1038/ncomms9700[2] Zakri, C.; Blanc, C.; Grelet, E.; Zamora-Ledezma, C.; Puech, N.; Anglaret, E.; and Poulin, P. Liquid crystals ofcarbon nanotubes and graphene. Phil. Trans. R. Soc. A., 371, 20120499, pp 1-15 (2013)[3] Zamora-Ledezma, C.; Puech, N.; Zakri, C.; Grelet, E.; Moulton, S. E.; Wallace, G. G.; Gambhir, S.; Blanc, C.;Anglaret, E.; and Poulin, P. Liquid Crystallinity and Dimensions of Surfactant-Stabilized Sheets of ReducedGraphene Oxide. J. Phys. Chem. Lett., 3 (17), pp 2425–2430 (2012