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the individual contract 2020.00252. CEECIND and several projects PTDC/QUI- LA/P/0140/2020, LAQV-REQUIMTE (LA/P/0008/2020). LS4FUTURE Associated Laboratory (LA/P/0087/2020) Publisher Copyright: © 2023 The Author(s) The exploration of novel long-lived near-infrared (NIR) luminescent materials has attracted significant attention due to their applications in optical communications, anticounterfeiting, and bioimaging. However, these materials usually present low photoluminescence quantum yields and low photo- and chemical stability. Novel emitters that overcome these limitations are in demand. In this study, NIR emission was achieved using widely available, sustainable, and non-toxic materials through the synthesis of sulfur-doped zeolites, with different S/Cl ratios. With a combination of computational calculations (TD-DFT) and spectroscopic data, this emission was assigned to the radiative decay of excited triplet states of [S3]2- clusters, which resulted in a remarkably high Stokes shift (1.97 eV, 440 nm) and an average decay time of 0.54 ms. These new materials present high stability, external quantum efficiency of up to 17%, and a long-lived NIR emission, placing these compounds in a unique position to be used in applications demanding NIR emitters. publishersversion published

In this study, we reported the use of X-ray microtomography (µCT) as a new analytical tool to investigate better the dispersion of natural filler in the polymer matrix. The pre-treated sugarcane bagasse (SCB), richer in cellulose, was first functionalised by hexamethyldisiloxane (HMDS) and then added (10, 20 and 30 wt% filler) to low-density polyethylene (LDPE) by melt mixing. The microstructure organization of the cellulose in the composites was studied using 3D and 2D µCT images, where it was possible to obtain an in-depth morphological and morphometric analysis. Thus, the synergistic effect of the filler on the mechanical properties of the polymer matrix as a function of surface chemistry was well clarified without the need of a large number of micrographs as is required to show the quality of dispersion using conventional imaging techniques. The characterisation method reported here is an easy, non-destructive and powerful way to characterise the cellulose fibres dispersion in LDPE-based composites and it can be applied to other fillers and polymer matrices.

Cellulose nanocrystals (CNC) were isolated from Munguba (Pseudobombax munguba) fibers and then functionalized with octadecyl isocyanate. Nanocomposites based on poly(butylene adipate-co-terephthalate) (PBAT) were prepared with different concentrations of cellulose nanocrystals (3, 5 and 7 wt%). We show that the addition of functionalized CNC leads to PBAT-based nanocomposites with enhanced thermal, rheological and mechanical performances, maintaining the biodegradability of the matrix. The better properties of the nanocomposites were related to the optimal amount and the uniform dispersion of CNC in PBAT. The study here presented expands the application of Munguba fibers, exploring their use to prepare PBAT-based biodegradable nanocomposites with improved properties. These nanocomposites have potential for replacement the conventional polymers in future applications with the advantage of exhibiting biodegradability.

openaire: EC/H2020/788489/EU//BioELCell A major challenge exists in the preparation of scaffolds for bone regeneration, namely, achieving simultaneously bioactivity, biocompatibility, mechanical performance and simple manufacturing. Here, cellulose nanofibrils (CNF) are introduced for the preparation of scaffolds taking advantage of their biocompatibility and ability to form strong 3D porous networks from aqueous suspensions. CNF are made bioactive for bone formation through a simple and scalable strategy that achieves highly interconnected 3D networks. The resultant materials optimally combine morphological and mechanical features and facilitate hydroxyapatite formation while releasing essential ions for in vivo bone repair. The porosity and roughness of the scaffolds favor several cell functions while the ions act in the expression of genes associated with cell differentiation. Ion release is found critical to enhance the production of the bone morphogenetic protein 2 (BMP-2) from cells within the fractured area, thus accelerating the in vivo bone repair. Systemic biocompatibility indicates no negative effects on vital organs such as the liver and kidneys. The results pave the way towards a facile preparation of advanced, high performance CNF-based scaffolds for bone tissue engineering.

Nanocomposite production using nanocellulose has been widely investigated based on all the features that nanocellulose can contribute to the composites properties, such as greater tensile strength, higher elastic modulus, higher viscosity, lower weight, barrier properties; it may work as catalyzer, modify the brittleness, change the glass transition in thermoset polymers among others. Meanwhile there are many challenges in this topic, mainly correlated to the incorporation of cellulose nanoparticles and how to get a good dispersion into the polymeric matrices. Therefore the nanocomposite preparation method is the key to obtain better properties and a good final material. Thus this chapter will deal with some strategies that are indispensable for the production of nanocellulose-based nanocomposites with good dispersion into thermoplastic and thermosetting polymers. Also some chemical modifications are discussed to improve the nanoparticles dispersion as well.

This paper reports the study on the synthesis of poly(e-caprolactone)—PCL by ring-opening polymerization (ROP) of e-caprolactone (CL) monomer with focus on mathematic developing of the growth mechanisms of polymer chain. Kinetics and mathematical modeling of ROP of CL was carried out to replicate the different experimental conditions. The computational results of conversion and molecular weight of the polymer were found to be comparable with the experimental results of nuclear magnetic resonance (NMR) spectroscopy and showed that the polymerization is highly dependent on the moisture (ROH). Moreover, parametric studies have shown how the concentrations of octanoic acid and catalyst affect the conversion and molecular weight of the polymer. The study here presented provides further understanding of synthesis of PCL, reporting mathematical models of PCL synthesis which can be used for predicting the characteristic of this biocompatible and biodegradable polymer.

Homogeneous dispersion of carbon nanotubes (CNTs) in polymers has significantly improved their processing and application as nanomaterials. Generally, CNTs tend to agglomerate due to their high aspect ratios and strong van der Waals interaction. Surface functionalization appears to be a solution to this problem. This study presents a controlled dispersion of carbon nanotubes in polyethylene through surface modification using a mixture of concentrated acid and octadecylamine (ODA). CNTs were characterized by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, and transmission electron microscopy. The results confirmed that carboxyl and alkane groups were successfully introduced on CNT surfaces. The acid- and amine-functionalized carbon nanotubes were dispersed in four solvents with different polarities (water, ethanol, acetone, and xylene) to correlate the degree of dispersion of CNT with their polarity. The results showed that CNT dispersion stability strongly depends on solvent and carbon nanotube polarities after the functionalization step. The nanohardness and tensile tests showed that the addition of CNTs, especially the functionalized with ODA, leaded the polymer harder, increasing its Young’s modulus and tensile strength. However, its toughness and deformation capacity were reduced. The potential applications of CNT-based polymer nanocomposites broaden considerably due to the surface engineering of carbon nanotubes.

The effects of amine-modified graphene oxide on dispersion and micro-hardness of epoxy based nanocomposites are reported. Graphene oxide was prepared by the modified Hummers method followed by hexamethylenediamine functionalization. Analysis conducted through Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy-based infrared spectroscopy show that the functionalization process effectively promoted a replacement of oxygen with amine groups while simultaneously creating defects in the graphitic structure. An increase in hardness was observed for the developed nanocomposites.

Polyesters produced from cyclic monomers, including polylactic acid (PLA), polycaprolactone (PCL) and polybutylene terephthalate (PBT), are widely used in different applications, ranging from household items to medical implants. These polymers can be produced by various processes, but ring-opening polymerization (ROP) occupies an important position. In this sense, ROP represents the foremost route used by both academia and industry to synthesize these polymers. In this review, we discuss the synthesis of PLA, PCL, PBT and some of their copolymers by ROP, focusing on polymerization kinetics and molecular weight control. We also revisit the most representative deterministic mathematical models for ROP to produce these polymers. We formulate a step-by-step guide on how to combine the method of moments in modeling the synthesis of polymers by ROP, including details on how to handle multiple summations in the system of Ordinary Differential Equations generated from the modeling.

In this study, the effects of cellulose nanocrystals modified with octadecyl isocyanate on rheological, mechanical and degradation properties of nanocomposites based on poly (butylene adipate-co-terephthalate) (PBAT) were reported. Nanocomposites were prepared by melt mixing procedure of PBAT with 3, 5 and 7 wt% cellulose nanocrystals. The increase of PBAT-based nanocomposites mechanical strength was discussed as a function of the cellulose nanocrystals surface chemistry, and the optimal amount of nanofillers in the nanocomposites, whereas the biodegradation rate of the polymer was related to the cellulose nanocrystals hydrophobicity. The study here presented promotes further understanding of cellulose nanocrystals functionalization and its effect on the overall properties of polymeric nanocomposites.

This review describes the use of cellulose nanocrystals (CNC) as fillers in biodegradable polymer matrices over the past few years. The preparation and characterization of CNC-based nanocomposites are highlighted here with a focus on thermophysical and mechanical properties. The characterization and isolation of nanocellulose from different raw material sources are discussed in detail, as well as different surface modifications. The addition of CNC in biodegradable polymer, combined with nanocellulose surface engineering and driven by sustainability trends, has the potential to impact various industrial sectors. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Carbon nanotube (CNT) reinforced high-density polyethylene (HDPE) composites were prepared by a melt mixing procedure. The mechanical properties were analyzed using a central composite design where...

This study presents the effect of dodecylamine (DDA) functionalization of carbon nanotubes (CNTs) on the thermo-physical and mechanical properties of high-density polyethylene (HDPE) based composites. Here, we showed that the functionalization with DDA improved the dispersion of the CNTs as well as the interfacial adhesion with the HDPE matrix via non-covalent interactions. The better dispersion and interaction of CNT in the HDPE matrix as a function of the surface chemistry was correlated with the improved thermo-physical and mechanical properties.

Here, we investigated the biocompatibility of a bioactive sodium calcium silicate glass containing 2.6 mol% Nb2O5 (denoted BGPN2.6) and compare the results with the archetypal 45S5 bioglass. The glass bioactivity was tested using a range of in vitro and in vivo experiments to assess its suitability for bone regeneration applications. in vitro studies consisted of assessing the cytocompatibility of the BGPN2.6 glass with bone-marrow-derived mesenchymal stem cells (BM-MSCs). Systemic biocompatibility was verified by means of the quantification of biochemical markers and histopathology of liver, kidneys, and muscles. The glass genotoxicity was assessed using the micronucleus test. The regeneration of a calvarial defect was assessed using both qualitative and quantitative analysis of three-dimensional microcomputed tomography images. The BGPN2.6 glass was not cytotoxic to BM-MSCs. It is systemically biocompatible causing no signs of damage to high metabolic and excretory organs such as the liver and kidneys. No mutagenic potential was observed in the micronucleus test. MicroCT images showed that BGPN2.6 was able to nearly fully regenerate a critical-sized calvarial defect and was far superior to standard 45S5 Bioglass. Defects filled with BGPN2.6 glass showed over 90% coverage compare to just 66% for 45S5 Bioglass. For one animal the defect was completely filled in 8 weeks. These results clearly show that Nb-containing bioactive glasses are a safe and effective biomaterial for bone replacement.

In vitro and in vivo experiments were undertaken to evaluate the solubility, apatite-forming ability, cytocompatibility, osteostimulation, and osteoinduction for a series of Nb-containing bioactive glass (BGNb) derived from composition of 45S5 Bioglass. Inductively coupled plasma optical emission spectrometry (ICP-OES) revealed that the rate at which Na, Ca, Si, P, and Nb species are leached from the glass decrease with the increasing concentration of the niobium oxide. The formation of apatite as a function of time in simulated body fluid was monitored by 31P Magic Angle Spinning (MAS) Nuclear magnetic resonance spectroscopy. Results showed that the bioactive glasses: Bioglass 45S5 (BG45S5) and 1 mol%-Nb-containing-bioactive glass (BGSN1) were able to grow apatite layer on their surfaces within 3 h, while glasses with higher concentrations of Nb2 O5 (2.5 and 5 mol%) took at least 12 h. Nb-substituted glasses were shown to be compatible with bone marrow-derived mesenchymal stem cells (BMMSCs). Moreover, the bioactive glass with 1 mol% Nb2 O5 significantly enhanced cell proliferation after 4 days of treatment. Concentrations of 1 and 2.5 mol% Nb2 O5 stimulated osteogenic differentiation of BMMSCs after 21 days of treatment. For the in vivo experiments, trial glass rods were implanted into circular defects in rat tibia in order to evaluate their osteoconductivity and osteostimulation. Two morphometric parameters were analyzed: (a) thickness of new-formed bone layer and (b) area of new-formed subperiostal bone. Results showed that BGNb bioactive glass is osteoconductive and osteostimulative. Therefore, these results indicate that Nb-substituted glass is suitable for biomedical applications.

Environmental concerns and cost reduction have encouraged the use of natural fillers as reinforcement in polymer composites. Currently, a wide variety of reinforcement, such as natural fibers and nanocellulose, are used for this purpose. Composite materials with natural fillers have not only met the environmental appeal, but also contribute to developing low-density materials with improved properties. The production of natural fillers is unlimited around the world, and many species are still to be discovered. Their processing is considered beneficial since the natural fillers do not cause corrosion or great wear of the equipment. For these reasons, polymer reinforced with natural fillers has been considered a good alternative for obtaining ecofriendly materials for several applications, including the automotive industry. This review explores the use of natural fillers (natural fibers, cellulose nanocrystals, and nanofibrillated cellulose) as reinforcement in polymer composites for the automotive industry.

Made available in DSpace on 2019-10-06T17:00:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In the present study, we report the preparation of antifungal and non-cytotoxic polymer nanocomposites with potential application in biomedical materials. Dodecanethiol-protected silver nanoparticles (AgNPs-DDT) were synthesized by a reduction/precipitation method and dispersed in chloroform to obtain stable colloidal dispersions. PBAT-based nanocomposites containing 0.25, 0.5 and 2 wt% AgNPs-DDT were prepared by casting method. The incorporation of AgNPs-DDT in PBAT matrix resulted in nanocomposites which combine improved mechanical performance and antifungal properties with a non-cytotoxic characteristic. School of Chemical Engineering University of Campinas (UNICAMP) Brazilian Nanotechnology National Laboratory (LNNano) Brazilian Center for Research in Energy and Materials (CNPEM) Department of Oral Biosciences and Diagnosis Institute of Science and Technology Universidade Estadual Paulista (UNESP) Physiological Science Department Piracicaba Dental School University of Campinas (UNICAMP) Instituto de Macromoléculas Professora Eloísa Mano (IMA) Universidade Federal do Rio de Janeiro (UFRJ) Department of Oral Biosciences and Diagnosis Institute of Science and Technology Universidade Estadual Paulista (UNESP) FAPESP: 2016/08595-1 FAPESP: 2016/09588-9

Carbon nanotubes (CNTs) have been studied extensively by researchers from different areas, which has led to improvements in their synthesis and characterization, and an ever-increasing range of applications has emerged. This chapter highlights various approaches to the synthesis and characterization of CNTs, as well as recent research progress on their potential applications as reinforcements in polymer nanocomposites, electronic devices, and biomedical materials. A brief history of CNTs and their properties have been addressed in other sections. Finally, the main methods to overcome the key barriers that limit the application of CNTs are presented herein on the basis of experimental and theoretical studies.

The surface modification of carbon-based nanomaterials, including carbon nanotubes (CNTs) and graphene oxide (GO), is advantageous for tailoring their dispersion in different solvents, as well as polymer matrices. Although the surface modification methodology of such nanomaterials is well established, the relationship between functionalization and interaction with the surrounding environment (solvents or polymers) – particularly repulsion/attraction forces that govern the clusters’ formation – is still not well understood to date. Herein, the dispersion of pristine and oxygenated/amino-functionalized CNTs and GO in different solvents were studied qualitatively (by optical microscopy and visual observations of dispersion tests) and quantitatively (by UV–Vis spectroscopy), and the repulsion/attraction process was explained based on π-π* transitions between CNT or GO and solvents. We found that both CNT and GO can have good dispersion in water, N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF), and the key to this behavior is the precise functionalization control, including orientation and type of functional group. In this sense, the introduction of functional groups improves the interaction quality of CNT and GO due to nanoscale attraction, and at the same time, enhances their orientation due to steric effect. The present study is expected to contribute to carbon-based nanomaterials’ surface engineering, which may be useful for researchers from different fields, such as carbon nanostructures, materials chemistry, and polymer nanocomposites.

The effect of carbon nanotube treatment on the mechanical property of polyethylene/carbon nanotube composite (HDPE/CNT) was investigated. CNTs were initially treated with HCl and then with H 2 SO 4 /HNO 3 . Nanocomposites reinforced with untreated and treated CNTs were prepared by a mechanical mixture of the molten polymer. The results demonstrated a correlation among the surface treatment, dispersion and mechanical properties of HDPE/CNT composites. Raman spectroscopy and TGA analysis showed that both acid treatments removed efficiently amorphous carbon and residual metal catalysts of CNTs. However, these treatments not only removed impurities, they also decreased the crystallinity degree of CNTs due to the addition of oxygenated functional groups to the CNTs walls, as observed by XPS analysis. SEM micrographs revealed that the functional groups improved the CNTs dispersion in the polymeric matrix, resulting in an improvement of the mechanical properties of nanocomposites.

International audience; Cellulose nanocrystals (CNCs) are considered as one of the most attractive renewable reinforcements for biodegradable polymers due to their promising properties and broad range of applications in several fields. However, the knowledge of CNCs effect on the overall properties of these CNC-based nanocomposites is not fully clarified. This review proposes a comprehensive understanding on the effect of CNCs on the rheological, thermal, mechanical, barrier and biodegradation properties of the main biodegradable polymers. This further understanding is expected to facilitate progress in various sectors of nanotechnology and materials science.

In this work, it was performed a dispersion study of carbon nanotubes (CNTs) functionalized with carboxylic and alkane groups in various solvents. CNT was functionalized using H 2 SO 4 /HNO 3 and subsequently functionalized by dodecylamine (DDA). Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy were used to characterize the CNTs at each step of the surface modification. The dispersion state of CNTs in the solvents was evaluated by Optical microscopy and visual observations. The evaluation of the solvent influence itself was also made. Results confirmed the presence of oxygen-containing and alkane groups on CNTs surfaces. The dispersion stability was strongly dependent on the solvent and carbon nanotubes surface interactions, which can vary with the chemical nature of the solvent. The study of the surface modifications and the degree of carbon nanotubes dispersion is relevant to enhance the full understanding of its applications.

Graphene is a new member of the nanocarbon family that has revolutionized the field of materials science and has attracted much attention due to its exceptional properties. Recent progress has shown that graphene-based nanocomposites can be used in nanoelectronics, touch screens, optics, catalysis, supercapacitors, fuel cell transistors, flexible electronics, H2 storage, and polymer nanocomposites. The functionalization is a surface modification much used to reduce the cohesive force between the graphene sheets and also to manipulate the physical and chemical properties. The aim of this book was to provide a comprehensive scientific progress of graphene, containing topics such as synthesis, characterization, and application of functionalized graphene. The characterization of the functionalized graphene is extremely important for determining the physicochemical properties of the material obtained after the functionalization treatments. However, this characterization is rarely addressed in books or in review articles. Generally, the functionalization reviews are too wide-ranging, discussing the functionalization of various materials (e.g., nanomaterials) or too specific, analyzing only one functionalization agent (with some specific chemical group, for example). This book, however, proposes to discuss the functionalization of one of the most widely used nanomaterials in recent years: graphene. Thus, the reader will find information on graphene functionalization, using several functionalization agents, in the same book.

Polyamide 6 (PA6)/layered double hydroxide (LDH) nanocomposites were prepared by in situ polymerization with different amount (1, 2, 3 wt%) and type (Zn/Cr-L and Zn/Cr-P) of LDHs. The thermal and mechanical properties and water absorption capacity of PA6/LDH nanocomposites were investigated and have shown that the addition of LDHs increases the crystallinity of the polymer and improves their mechanical properties, while decreases the water absorption capacity due to a barrier effect of LDHs. A correlation between mechanical properties and water absorption capacity was observed and discussed. This study provides new strategies for tuning PA6-based nanocomposite properties, leading a progress in the development on the advanced polymer materials.

The focus of this study is to evaluate the effect of carboxyl and amino functionalization of multiwalled carbon nanotubes on the mechanical property of the epoxy resin filled with modified carbon nanotubes. The carbon nanotubes were treated with sulfuric and nitric acids and also with hexamethylenediamine. The presence of acid and amine chemical groups on the carbon nanotube surface was confirmed by X-ray photoelectron spectroscopy. The composites were produced with epoxy resin and modified carbon nanotubes. Vickers hardness tests were carried out on the composites and neat resin. The results showed an increase of hardness in the composite prepared with functionalized carbon nanotubes. This phenomenon is due to the fact that the chemical interaction between modified carbon nanotube and epoxy resin is much stronger than between pristine carbon nanotube and epoxy resin. This stronger interaction is related to the presence of functionalized carbon nanotubes.

Carbon nanotubes (CNTs) were treated using acids and Hexamethylenediamine (HMDA). The presence of acid and amine chemical groups on the CNTs surface was confirmed by X-ray Photoeletron Spectroscopy (XPS). The nanocomposites were produced with epoxy resin and modified CNTs. Vickers hardness tests were carried out on the composites and neat resin. Results showed an increase in the sample hardness prepared with functionalized CNTs. This phenomenon is due to the compatibility between modified CNTs and epoxy resin is much higher than between bare CNTs and epoxy resin. This higher compatibility is related to the strong interfacial interaction between the functionalized CNTs and the polymer.

Electrospun ultrathin polymer fibers hybridized with bioactive ceramics find use in many biomedical applications due to their unique and versatile abilities to modulate structure–performance relationships at the nano–bio interface. These organic–inorganic hybrid fibers present synergies that are otherwise rare, even when the precursors are used individually, such as bioactivity in polymers and stiffness–toughness balance in bioactive ceramics. Despite these unique advantages, a comprehensive and timely review on this important topic is still missing. Herein we describe the most recent and relevant developments on electrospun ultrathin polymer fibers hybridized with bioactive ceramics, with emphasis on bone tissue regeneration. This review addresses the preparation of bioactive ceramics, particularly (nano) hydroxyapatite (HA; nHA) and bioactive glass (BG), which stand out as the ceramics of interest for bone regeneration. The anatomy and mechanical properties of bone as well as fundamental tissue–scaffold interaction mechanisms are covered. The process–structure–property relationships of electrospun ultrathin fibers are discussed in detail from a technical standpoint, as well as fabrication strategies, process variables, characterization methods, and biological requirements (in vitro and in vivo performances). Finally, we highlight the major challenges and outline perspectives to pave the route for the next-generation hybrid materials for bone tissue engineering.