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New monomeric ligands inserted in ruthenium polypyridine complexes generated metallomonomers that were copolymerized with NBE by ROMP resulting in metallopolymers.

Spin coating has been the primary choice of deposition method used in the assembly of lab-scale perovskite solar cells. Other deposition methods are still lagging behind, both in terms of device ef...

The combination of computational methods and advanced characterization techniques is used to highlight the role of the intramolecular hydrogen bond in thienyldiketopyrrolopyrrole (ThDPPTh) copolyme...

The increasing market demand for smaller products requires the development of micromachining processes. This, in turn, enhances the importance of knowledge about the phenomenon of chip formation and its characteristics at the microlevel. Conventional machining generally assumes that the tool cutting edge is perfectly sharp, and that it usually does not affect the chip formation process. However, in micromachining, the magnitude of the edge radius (re) is often the same as that of the chip thickness, thus significantly affecting the process. Moreover, the study of chip formation at the microlevel is even more complex. In micromachining, as the chip thickness decreases, it reaches a minimum thickness at which a chip is still formed, called the minimum uncut chip thickness (MUCT). Therefore, the purpose of this work is to use an experimental method, based on milling, to reach the MUCT (hmin) by simulating a micromilling operation. AISI H13 steel was used in two conditions: hardened and as received, with around 60 and 25 HRc, respectively. The experiments were performed according to a novel method simulating end milling in orthogonal cut. It was found that hmin varied from 0.56re to 2.5re, and that this range depends not only on re but also on the material being machined and on the mechanical compliance of all the equipment used in the test. Based on the theory of contact mechanics, it was possible to explain that a chip is formed only after the cutting edge has attained the necessary stresses to cause failure of the material being tested, and this knowledge is fundamental to understand the occurrence of hmin. In addition, the method used here was successful in reaching hmin values typically obtained in milling conditions. Using the same method proposed herein, future studies of MUCT can be performed employing even conventional machine tools.

Among the wide range of structural polymers currently available, this work deals with high-density polyethylene (HDPE). The typical viscoelastic behavior of this material is not trivial to model an...

1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin, using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways, we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction. In general, the procedure is suitable for characterizing reactions involving the formation of solid products from liquid reagents, with some adaptations concerning the reaction model.

Stability of π-conjugated organic materials remains a critical issue for applications in which these materials and devices based on them are exposed to ambient conditions.

Made available in DSpace on 2022-05-01T11:54:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-15 The excessive concentration of nanomaterials and pesticides in industrial products, food, and in the environment can be a risk to human health. Exposure to these materials can occur through inhalation, dermal contact, or oral ingestion, which depends directly on the type of products we are exposed to. Extensive studies about the individual action of these compounds have been described. However, the effect of these mixtures (nanoparticles and pesticides, for instance) requires more investigation. Here, we evaluated by phase-contrast microscopy the individual and mixture effects of silver nanoparticles (AgNp) and thiram pesticide on mimetic systems of the lipid bilayer structure of the plasma membrane using DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) giant unilamellar vesicles (GUVs). Besides, the effect of thiram pesticide on DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) multilamellar vesicles containing AgNp (encapsulated) was also evaluated by surface-enhanced Raman scattering (SERS). The results showed a synergetic effect of the AgNp and thiram mixture, which lead to a loss of phase contrast intensity and rupture of the lipid bilayers. The synergetic effect was ascribed to the strong interaction AgNp-thiram through Ag-S bond formation. São Paulo State University (UNESP) School of Technology and Applied Sciences São Carlos Institute of Physics Universityof São Paulo São Paulo State University (UNESP) School of Technology and Applied Sciences

Chitosan-based glycerol-plasticized membranes were prepared aiming to develop low-cost and biocompatible material for wound dressing. They were produced by casting/solvent evaporation, and their formation mechanisms were attributed to intra- and inter-hydrogen bonds between materials. The results show that the glycerol acted as plasticizer and changed the proliferation of fibroblast cells on chitosan membranes. A high increase in the contact angle between water and membrane was observed comparing pure chitosan (more hydrophilic) and chitosan-glycerol (more hydrophobic) membranes. The angle values were found to be ~ 40 and ~ 130 degrees for chitosan and chitosan/glycerol 30% (w/w) membranes, respectively. In comparison with pure chitosan, glycerol-mixed membranes showed lower glass transition temperatures and are less brittle when handling. The antibacterial properties of such membranes against Gram-negative (E. coli) and Gram-positive (S. aureus and B. Cereus) microorganisms were tested, showing efficient growth inhibition. In vitro studies over fibroblast cells using plasticized membranes demonstrated good viability and enhanced cell proliferation in comparison with those composed of pure chitosan. Such results suggest that the as-prepared chitosan-glycerol membrane is a promising material for use as wound dressing in tissue engineering applications.

The exploration and harnessing of the renewable sources of energy, in addition to that of the conventional sources, has become significantly prominent with the increasing global energy demands for the continuous production of the energy for world consumption. Among these sources, for different applications, the approach of harnessing of the solar energy using the solar cells based on organic materials has already been envisaged as an alternative to that of using the solar cells based on silicon, with much of focus on the polymer based solar cells, and more recently perovskite solar cells. Such applications require the unique property of flexibility of the solar cells based on solution processable active materials. In addition, as the required area of the solar cells for these applications can be very large, the upscaling of the manufacturing rate and the size of these solar cells requires the manufacturing of these solar cells with faster techniques of roll-to-roll printing, which allow the faster and massive commercial scale for production. This review gives a detailed account of the recent progress and the development of the roll-to-roll printing technology for the polymer and perovskite solar cells, including the roll-to-roll-compatible materials and processes, over few years.

The present work reports the development of chitosan-based films for application as protective layer for natural foods such as fruits and vegetables. Chitosan is a biopolymer known for its antibacterial and antifungal properties that when combined with its biocompatibility and biodegradability can be widely applied in areas such as cosmetic, pharmaceutical and food industry. In this work, thin films based on chitosan were obtained by the drop-casting method using glycerol to enhance elasticity and hydrophobic character. Such properties are desirable to form a protective layer that is not highly soluble in water. The results showed that the bactericidal character of chitosan against gram-positive and gram-negative bacteria remains after plasticization. Strawberries coated with chitosan/glycerol 30% films (Chi/30%Gly) showed resistance against gray fungus attack and an insignificant alteration in their flavor, appearance, aroma and texture. In other words, the chitosan film protected the strawberry from fungi attack, showing its great potential as edible coating for fruits and vegetables.

Dielectric gratings that couple optical fibers and planar waveguide circuits are key for optical-to-electronic (electronic-to-optical) signal conversion, but their applicability to platforms that require broader bandwidths and higher capacity is limited by their single-wavelength response. Herein, we present the design of a quasi-periodic grating coupler with multiband fiber-to-waveguide (waveguide-to-fiber) coupling response, where the grating consists of a periodic repetition of unit cells made of alternating silicon and air grooves according to the Fibonacci sequence. Through finite-difference time-domain (FDTD) calculations, we show that this new device could be used for coupling multi-wavelength fiber modes in a single grating structure. The results were obtained for fibers operating in the wavelength range from 1000 nm to 2000 nm, but the concept can be readily extended to other frequency ranges. Moreover, the allowed modes in the grating are almost insensitive to fiber misalignments and small fabrication errors for high Fibonacci steps, which is useful when alignment of optical components is impractical. It is hoped that properly designed gratings overlapping multiple modes may lead to ultra-broadband fiber-waveguide couplers that can cope with the growing demand for higher capacity and bandwidth in optical communications.

Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green and ecofriendly synthesis approach is a promising way to produce these nanostructures with desired properties with less risk of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications. Moreover, they are more efficient, non-toxic, and cost-effective. This review mainly focuses on the recent state-of-the-art advancements in the green synthesis approach for ZnO and TiO2 nanostructures and their applications. The first section summarizes the green synthesis approach to synthesize ZnO and TiO2 nanostructures via different routes such as solvothermal, hydrothermal, co-precipitation, and sol-gel using biological systems that are based on the principles of green chemistry. The second section demonstrates the application of ZnO and TiO2 nanostructures. The review also discusses the problems and future perspectives of green synthesis methods and the related issues posed and overlooked by the scientific community on the green approach to nanostructure oxides.

Much has been reported on the effects of air action on the physical entities related to the transport processes in organic solar cells, for example, the electronic mobility, the lifetime of the charge carriers and the recombination kinetics. These effects have a direct impact on the series and parallel resistances (Rs and Rsh) of the solar cell, but studies of the action of the air environment on these resistances have been little explored. Here we present an experimental study of the environment action on an ITO/PEDOT:PSS/PTB7-Th:PC71BM/Ca/Al device, exploring mainly the variation of the series and the shunt resistances with the air exposure time. We used the classical equation of the current–voltage of an equivalent circuit of a solar cell to fit the experimental results, and used Rs and Rsh as adjustment parameters. We also correlated these resistances with the fill factor by the help of an approach developed by M. A. Green in 1982.

Defectively manufactured and deliberately damaged composite laminates fabricated with different continuous reinforcing fibres (respectively, carbon and glass) and polymer matrices (respectively, thermoset and thermoplastic) were inspected in magnetic resonance imaging equipment. Two pulse sequences were evaluated during non-destructive examination conducted in saline solution-immersed samples to simulate load-bearing orthopaedic implants permanently in contact with biofluids. The orientation, positioning, shape, and especially the size of translaminar and delamination fractures were determined according to stringent structural assessment criteria. The spatial distribution, shape, and contours of water-filled voids were sufficiently delineated to infer the amount of absorbed water if thinner image slices than this study were used. The surface texture of composite specimens featuring roughness, waviness, indentation, crushing, and scratches was outlined, with fortuitous artefacts not impairing the image quality and interpretation. Low electromagnetic shielding glass fibres delivered the highest, while electrically conductive carbon fibres produced the poorest quality images, particularly when blended with thermoplastic polymer, though reliable image interpretation was still attainable.

PROCESSING AND APPLICATION OF POLYMERIC BIOMATERIALS: RECENT ADVANCES AND PERSPECTIVES. Biomaterials have been intensively investigated due to the increase in the elderly population and high prevalence of several disorders, such as cardiovascular and orthopedic diseases. Polymeric and composite polymeric materials in combination with different processing techniques, such as electrospinning, solution blow spinning, ultrathin film preparation, and 3D printing are promising for obtaining biomaterials with patient-specific applications. Here, we provide a review on recent advances and perspectives for synthetic and natural polymers as well as composites in the design of biomaterials. After introducing basic information about biomaterials, we describe the fundamentals of manufacturing techniques and highlight possible biomedical applications. Made available in DSpace on 2022-03-18T07:15:01Z (GMT). No. of bitstreams: 1 P-PROCESSAMENTO-E-APLICACAO-DE-BIOMATERIAIS-POLIMERICOS-AVANCOS-RECENTES-E.pdf: 1019144 bytes, checksum: b17958bcf825b201a38ed0548aa2d350 (MD5) Previous issue date: 2022

Hot embossing is a technique used to fabricate high-precision and high-quality polymeric components that combines low costs with high aspect ratio fidelity replication. In this study, we manufactured two aspherical Fresnel molds employing the single-point diamond turning process on an electrolytic copper workpiece, one with 10 μm constant height 30 zones and the other with 250 μm constant width 40 zones. The micromachined mold reproduced PMMA convex-plane lens optical quality replicas through the micro hot embossing technique. We used a scanning electron microscope (SEM), spectrophotometry, and non-contact optical profilometer to evaluate the replication fidelity qualitatively: the lens mold and the fine three-dimensional microstructures on the PMMA substrate surfaces. The results of the surface finish of the diamond machined mold sample are in the range of 4.92 nm (areal average surface roughness Sa) and 6.04 nm (areal root-mean-squared roughness Sq), respectively, and the values for the replicas being 4.73 nm and 5.94 nm, respectively. The results demonstrated that the geometry form accuracy obtained of the microfeatures was at the submicron level with little viscoelastic recovery. The surface roughness in the nanometer level got successfully replicated.

Direct laser writing techniques are suitable for the high precision-patterning of 2D and 3D micro/nanostructures, featuring a variety of geometries and materials. Here, we demonstrated the use of laser-induced forward transfer with fs-pulses (fs-LIFT) to selectively transfer graphene oxide and poly(p-phenylene vinylene) patterns onto polymeric microstructures, fabricated by two-photon polymerization. The influence of different fs-LIFT experimental parameters on the width and height of the printed patterns was investigated. Upon optimum fs-LIFT parameters, we achieved homogeneous printed areas of both materials onto specific regions of the microstructures. Raman spectroscopy confirmed that fs-LIFT does not change the donor material upon transfer. Overall, this work demonstrates a promising strategy with precise printing capabilities, thus opening new opportunities for the development of photonic and optoelectronic devices.

Made available in DSpace on 2021-06-25T10:35:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Staatssekretariat für Migration Universidade Estadual Paulista Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Carbon-based composite nanomaterials, such as graphene oxide, have demonstrated a great potential for applications in several areas. The present work sought to obtain, via electrosynthesis, a composite material based on graphene oxide and iron oxyhydroxide deposited onto graphite pencil surface. The electrodes modifications by electrosynthesis was performed using the cyclic voltammetry technique. The graphene oxide and the electrosynthesized FeOOH cuboids were characterized by SEM-FEG, EDX. The cyclic voltammetry was used to characterize the electrochemical behavior of the graphite pencil electrode (PEG). The composites electrodes of PEG modified with GO/FeOOH (PEG/GO/FeOOH) were formed in two stages. In the first stage, there was the formation of FeHCF in PEG/GO, and subsequently, there was the formation of PEG/GO/FeOOH in alkaline medium. Engineering of Energy Campus of Rosana São Paulo State University (Unesp), Barrageiros Avenue 1881 Institute of Physics São Carlos USP – University of São Paulo Engineering of Energy Campus of Rosana São Paulo State University (Unesp), Barrageiros Avenue 1881 FAPESP: 2017/09123-9 FAPESP: 2017/17559-1

We report a paper-based electrochemical immunosensor made with sustainable materials to detect aflatoxin B1 (AFB1), a highly toxic, carcinogenic mycotoxin found in food. The immunosensor was prepared with a waterproof paper substrate and low-cost graphite-based conductive ink through a simple cut-printing method. The working electrode was functionalized with a drop-cast film of multiwalled carbon nanotubes (MWCNT)/chitosan on which a layer of anti-AFB1 monoclonal antibodies was immobilized covalently. The architecture of the immunosensor was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and electrochemical impedance spectroscopy (EIS), including the effective immobilization of the active layer of anti-AFB1. With EIS as the principle of detection, the immunosensor could detect AFB1 in the range from 1 to 30 ng&middot, mL&minus, 1, and detection limit of 0.62 ng&middot, 1. This sensitivity is sufficient to detect AFB1 in food according to regulatory agencies. The immunosensor exhibited good repeatability, reproducibility, stability, and selectivity in experiments with a possible interferent. Furthermore, detection of AFB1 in maize flour samples yielded recovery of 97&ndash, 99%, in a demonstration of the possible use of the paper-based immunosensor to detect AFB1 using extraction solutions from food samples.

Cellulose-based hydrogel materials prepared by regeneration from cellulose solutions in ionic liquids, or ionic liquid containing solvent mixtures (organic electrolyte solutions), are becoming widely used in a range of applications from tissue scaffolds to membrane ionic diodes. In all such applications knowledge of the nature of the hydrogel with regards to porosity (pore size and tortuosity) and material structure and surface properties (crystallinity and hydrophobicity) is critical. Here we report significant changes in hydrogel properties, based on the choice of cellulose raw material (α- or bacterial cellulose – with differing degree of polymerization) and regeneration solvent (methanol or water). Focus is on bioaffinity applications, but the findings have wide ramifications, including in biomedical applications and cellulose saccharification. Specifically, we report that the choice of cellulose and regeneration solvent influences the surface area accessible to a family 1 carbohydrate-binding module (CBM), CBM affinity for the cellulose material, and rate of migration through the hydrogel. By regenerating bacterial cellulose in water, a maximum accessible surface area of 33 m2 g−1 was achieved. However, the highest CBM migration rate, 1.76 μm2 min−1, was attained by regenerating α-cellulose in methanol, which also resulted in the maximum affinity of the biomolecule for the material. Thus, it is clear that if regenerated cellulose hydrogels are to be used as support materials in bioaffinity (or other) applications, a balance between accessible surface area and affinity, or migration rate, must be achieved.

3D foam scaffolds were produced in a “bottom-up” approach from lyophilised cationic cellulose nanofibril (CCNF) dispersions and emulsions (CCNF degree of substitution 23.0 ± 0.9%), using a directional freezing/lyophilisation approach, producing internal architectures ranging from aligned smooth walled micro channels, mimicking vascularised tissue, to pumice-like wall textures, reminiscent of porous bone. The open, highly porous architecture of these biomimetic scaffolds included mesopores within the walls of the channels. A combination of SEM and NMR cryoporometry and relaxometry was used to determine the porosity at different length scales: CCNF foams with aligned channels had an average macropore (channel) size of 35 ± 9 μm and a mesopore (wall) diameter of 26 ± 2 nm, while CCNF foams produced from directional freezing and lyophilisation of Pickering emulsions had mesoporous walls (5 ± 3 μm) in addition to channels (54 ± 20 μm). Glyoxal crosslinking both enhanced robustness and stiffness, giving Young's moduli of 0.45 to 50.75 MPa for CCNF foams with degrees of crosslinking from 0 to 3.04 mol%. Porosity and channels are critical scaffold design elements for transport of nutrients and waste products, as well as O2/CO2 exchange. The viability of MG-63 cells was enhanced on crosslinked, mechanically stiff scaffolds, indicating that these exquisitely structured, yet robust, foams could provide biomaterial scaffolds suitable for industrial applications requiring 3D cell culturing.

The manufacture of sensors using large-scale production techniques, such as roll-to-roll (R2R) processing, may fulfill requirements of low-cost disposable devices. Herein, we report the fabrication of fully-printed electrochemical sensors using screen-printed carbon electrodes coated with carbon black inks through slot-die coating within an R2R process. As a proof of concept, sensors were produced to detect the neurotransmitter dopamine with high reproducibility and low limit of detection (0.09 μmol L−1). Furthermore, fully-printed biosensors made with a tyrosinase-containing ink were used to detect catechol in natural water samples. Since slot-die deposition enables printing enzymes without significant activity loss, the biosensors exhibited high stability over a period of several weeks. Even more important, R2R slot-die coating may be extended to any type of sensors and biosensors with the possibility of large-scale manufacturing.

International audience; A finite-strain theory for the study of the overall behavior of polymeric gels containing microvoids is presented. The swollen porous polymeric gel is modeled as a two-component body composed of two incompressible materials, namely, an elastic porous polymer imbibed with a solvent. The chemical equilibrium is assumed to be preponderate at the interface between the porous polymer and its environment where the chemical potential of the solvent is fixed. The initially dry porous polymer undergoes large deformations induced by absorption of a solvent from the environment and mechanical loading. In this paper an attempt is made toward obtaining an estimation of the macroscopic responses of the swollen porous polymer to prescribed proportional loadings. To this end, a two-level representation of the material at hand for which the Representative Volume Element (RVE) imbibed with a solvent is a simple axisymmetric cylinder composed of a homogeneous matrix surrounding a spherical void, is considered. The numerical study addresses the situation where the RVE is subjected to prescribed axial and lateral overall stresses under conditions of constant overall stress triaxiality. For fixed values of the Flory-Huggins parameter and nominal concentration of the solvent, the overall stress-strain behavior of the RVE model, the influence of the initial porosity, and the prescribed stress triaxiality ratio have been obtained.

Made available in DSpace on 2020-12-12T02:40:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Universidade Estadual Paulista Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Sunlight is important to health, but higher exposure to radiation causes early aging of the skin and skin damage that can lead to skin cancers. This study aimed at producing a stable octyl p-methoxycinnamate (OMC)–loaded nanostructured lipid carrier (NLC) sunscreen, which can help in the photoprotective effect. NLC was produced by emulsification-sonication method and these systems were composed of myristyl myristate (MM), caprylic capric triglyceride (CCT), Tween® 80 (TW), and soybean phosphatidylcho-line (SP) and characterized by dynamic light scattering (DLS), zeta potential (ZP) measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and in vitro release studies. Pre-formulation studies were performed changing TW concentrations and no differences were found at concentrations of 1.0 and 2.0%. Two selected formulations were designed and showed an average size of 91.5–131.7, polydispersity index > 0.2, and a negative value of ZP. AFM presented a sphere-like morphology and SEM showed ability to form a thin film. DSC exhibited that the incorporation of OMC promoted reduction of enthalpy due to formation of a more amorphous structure. Drug release shows up to 55.74% and 30.57%, and this difference could be related to the presence of SP in this formulation that promoted a more amorphous structure; the release mechanism study indicated Fickian diffusion and relaxation. Sun protection factor (SPF) evaluation was performed using NLC and presented values around 40, considerably higher than those observed in the literature. The developed formulations provide a beneficial alternative to conventional sunscreen formulations. School of Pharmaceutical Sciences UNESP-São Paulo State Uni-versity, Rodovia Araraquara-Jau, km. 1 Department of Pharmacy School of Pharmacy Odontology and Nursing Federal University of Ceará Institute of Physics of São Carlos University of São Paulo School of Pharmaceutical Sciences UNESP-São Paulo State Uni-versity, Rodovia Araraquara-Jau, km. 1 CAPES: 001 FAPESP: 2014/22426-2

We report on the crystal morphology and Raman scattering features of high structural quality GaSb1-xBix alloys grown by molecular beam epitaxy with a high Bi content (x up to ∼0.10). The Raman spectra were measured at room temperature with different laser excitation wavelengths of 532 nm, 633 nm, and 785 nm. We observed well-defined Bi-induced Raman peaks associated with atomic Bin clusters and GaBi vibrational modes. Remarkably, some Bi-induced Raman modes were strongly enhanced when the laser energy was selected near an optical transition for the 5.8%Bi sample. This effect was attributed to a Raman resonant effect near an excited optical transition of the GaSbBi layer and has been used to identify the nature of the observed Raman peaks. acceptedVersion

A graphite-polyurethane composite electrode (GPUE) was modified with methacrylate molecularly imprinted with tetracycline (TC) as the template molecule for the first time. The work aimed to contrib...

Orientadora: Profª Drª Mathilde Julienne Gisèle Champeau Ferreira Dissertação (Mestrado) - Universidade Federal do ABC, Programa de Pós Graduação em Ciência e Engenharia de Materiais, Santo André, 2020. Para reduzir os efeitos colaterais da administração via oral ou via injeção de fármacos, a impregnação assistida por dióxido de carbono supercrítico (scCO2) tem sido usada para desenvolver novos sistemas de entrega de fármacos. Mesmo sendo um processo bem conhecido quanto a influência dos parâmetros de processo e quanto a influência das interações físico-químicas na impregnação de um composto em uma matriz polimérica, não há estudos sistemáticos sobre esses parâmetros na impregnação de polímeros com sistemas multicomponentes, como os extratos naturais. Apesar de não existir esse tipo de estudo, a impregnação dos sistemas multicomponentes tem ganhado a atenção devido a sua elevada bioatividade e baixa toxicidade se comparados a sistemas simples. O presente trabalho tem como objetivo identificar e explicar fenômenos específicos à impregnação simultânea de diferentes compostos em um polímero a fim de se otimizar a impregnação de sistemas multicomponentes. Para isso foram escolhidas duas matrizes poliméricas, o Poli(L-Ácido Láctico) (PLLA) e o Polietileno Linear de Baixa Densidade (PELBD), e a combinação de dois compostos entre a aspirina, o cetoprofeno e a carvona para realizar a impregnação dupla. As impregnações foram investigadas em duas condições, {60 ºC; 90 bar} e {80 ºC; 300 bar} por 3h. A quantidade de compostos impregnados foi determinada gravimetricamente e por HPLC, FTIR foi utilizado para verificar as interações entre o polímero e o composto e a análise de DSC foi utilizada para verificar o impacto da impregnação na microestrutura dos polímeros. Para o PLLA foram observados efeitos sinérgicos na impregnação do cetoprofeno com a aspirina e com a carvona na condição {80 ºC; 300 bar}. Essa sinergia ocorreu devido aos efeitos plastificantes e criogênicos dos compostos sobre a matriz polimérica que auxiliaram na impregnação dos compostos que possuíam alguma dificuldade de difusão na matriz polimérica. Para o PELBD não foram observadas impregnações com valores significativos, evidenciando a importância da interação entre a matriz e os compostos. Conclui-se então que, se a matriz possuir mobilidade em suas cadeias e for capaz de interagir com os compostos, a sinergia vai acontecer quando um composto for capaz de ter efeito criogênico e plastificante para auxiliar na difusão dos demais compostos. A liberação in vitro dos compostos também foi estudada. O mecanismo de liberação foi a difusão fickiana e de, maneira geral, a impregnação dupla tem liberação mais rápida do que a impregnação simples devido a mudanças na microestrutura do PLLA. In order to reduce the side effects of oral or injection drug administrations, the supercritical CO2 (scCO2) assisted impregnation has been used to develop new systems of local drug delivery. Even though this process is well known regarding the influence of the operational conditions and the influence of the physical-chemical interactions on the impregnation of one compound into a polymeric matrix, there is no systematic study about these parameters for multicompounds systems, such as natural extracts, and yet their impregnation has gained attention. The present study aimed to identify and explain the specific phenomena of the simultaneous impregnation of different compounds into a polymer in order to optimize the impregnation process of multicompounds systems. We have chosen a model of one polymeric matrix, Poly(L-Lactic Acid) (PLLA) or Linear Low-Density Polyethylene (LLDPE), and the combination of two compounds among aspirin, ketoprofen and carvone. The impregnation was investigated in two conditions, {60 ºC; 90 bar} and {80 ºC; 300 bar}, for three hours. The total impregnation yields were measured gravimetrically and using HPLC, FTIR analyses permitted to evaluate the interaction between matrix and compound, and DSC allowed evidencing the impact of the impregnation process on the PLLA microstructure. For PLLA, synergistic effects were observed on ketoprofen impregnation with aspirin and with carvone at {80 ºC; 300 bar}. This synergy occurred due to the compounds plasticizing and cryogenic effects in the polymeric matrix that helped the impregnation of the other compound that had some difficulty in the diffusion through the polymeric matrix. For LLDPE, no significant impregnation was observed, highlighting the importance of the interaction between the matrix and the compounds. In conclusion, if the matrix has chain mobility and is able to interact with the compounds, synergy will happen when a compound has cryogenic and plasticizing effect on the matrix to assist in the diffusion of the other compound. The compunds in vitro release was also studied. The release mechanism was Fickian diffusion and, in general, double impregnation was faster than single impregnation due to changes in the PLLA microstructure.

We employ X-ray diffraction, NMR and UV-vis spectroscopy techniques to shed light on the structure, molecular mobility and crystallization of a prototypical semiconducting polymer poly(3-(2′-ethylhexyl)thiophene) (P3EHT). Grazing-incidence X-ray diffraction (GIXD) and high-field 1H-1H double-quantum NMR reveal a tilt of the thiophene rings along the main chains, while high resolution 13C solid-state NMR methods show the presence of highly mobile side-chains. Taken together, the data reveal a high amount of free volume between adjacent chains in the crystalline phase, most likely owing to the additional steric hindrance from the branched ethyl group of the hexyl side chains. Additionally, the aforementioned methods allow us to confirm that crystallization in P3EHT occurs in a one-dimensional fashion along the polymer backbone. An extended model based on the Avrami principles is used to fit the experimental results to extract key parameters, such as nucleation rate and density, that govern these crystallization processes. The results show significantly reduced rates of crystallization in thin P3EHT thin films due to polymer chain confinement effects. This journal is

Helix 8 of the GPCR neurotensin receptor 1 is stabilised by specific lipid-protein interactions., G protein–coupled receptors (GPCRs) are the largest and pharmaceutically most important class of membrane proteins encoded in the human genome, characterized by a seven-transmembrane helix architecture and a C-terminal amphipathic helix 8 (H8). In a minority of GPCR structures solved to date, H8 either is absent or adopts an unusual conformation. The controversial existence of H8 of the class A GPCR neurotensin receptor 1 (NTS1) has been examined here for the nonthermostabilized receptor in a functionally supporting membrane environment using electron paramagnetic resonance, molecular dynamics simulations, and circular dichroism. Lipid-protein interactions with phosphatidylserine and phosphatidylethanolamine lipids, in particular, stabilize the residues 374 to 390 of NTS1 into forming a helix. Furthermore, introduction of a helix-breaking proline residue in H8 elicited an increase in ß-arrestin–NTS1 interactions observed in pull-down assays, suggesting that the structure and/or dynamics of H8 might play an important role in GPCR signaling.

Natural fibers (NFs) has been an interesting source for reinforcement in polymer composites due to their high availability, low production cost, and satisfactory performance for requirements of the...

We reveal early stages of self-organization of nanopatterns created by 2 keV Cs+ ion-beam irradiation of a Si surface coated with Au and a Ti adhesion layer. After ion-beam etching of the metallic layers, at normal incidence, we first observe distinct transient stages: (I) a dewetting-like pattern of grooves in the Si amorphized layer, sparsely populated with holes, followed by (II) the coexistence of rounded mounds and faceted holes distributed on a flat surface, the latter being an indication of the decisive role played by the crystalline/amorphous interface. Subsequently, the system evolves to stage III, a nanopattern of densely packed nanodots convoluted with a long-wavelength surface corrugation. A momentum-space analysis shows that stages (I) and (II) are identified, respectively, with channel-type and sphere-type quasi order.

In this work, curcumin nanocrystals (CCN) was used as fluorescence probes for monitoring the accelerated aging of high density polyethylene (HDPE) used in insulation of high-voltage cables. CCN has been synthesized and incorporated into HDPE matrix using hydrothermal process (HydP) at 202.65 kPa and temperatures of 60 °C and 120 °C. The apparent activation energy (EA) for CCN incorporation into HDPE matrix was 54.4 kJ/mol. The resulting nanocomposite HDPE-CCN has been characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and fluorescence spectroscopy (FS). The crystallinity of HDPE and HDPE-CCN determined by DSC were 71.27% and 70.30% respectively, suggesting that the presence of CCN does not modify significantly the microstructure of HDPE. Accelerated aging of HDPE-CCN samples was carried out and the stress to break ( $\varepsilon _{\mathrm {b}}$ ), Young’s modulus (E) and fluorescence intensity (FI) were used as measurements of HDPE degradation. Mechanical properties ( $\varepsilon _{\mathrm {b}},\mathrm {E}$ ) and FI measurements do correlate with age-related material degradation on the HDPE samples examined.

Quick-response (QR) codes are gaining much consideration in recent years due to their simple and fast readability compared with conventional barcodes. QR codes provide increased storage capacity and safer access to information, fostering the development of optical or printed smart tags as preferred tools for the Internet of Things (IoT). Herein, the combination of Yb3+/Er3+-doped NaGdF4 upconverting nanoparticles (UCNPs) with recovered plastic for the fabrication of sustainable screen-printed QR codes is reported. Their photothermal response under distinct power densities of the 980 nm laser irradiation (15���115 W cm���2) induces color-tuning and temperature sensing. This power dependence is exploited to design a double key molecular keylock accessed by a smartphone camera through the red (R), green (G), and blue (B) (RGB) additive color model and upconversion thermometry. The latter is based on the integrated areas of the 2H11/2���4I15/2 and 4S3/2���4I15/2 Er3+ transitions using the interconnectivity and integration into the IoT network of the mobile phone to download the temperature calibration curve of the UCNPs from a remote server. These findings illustrate the potential of QR codes-bearing UCNPs toward the design of smart tags for mobile optical sensing and anticounterfeiting., This project has received funding from the European Union's Horizon 2020 FET Open programme under grant agreement No 801305 (NanoTBTech). This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 823941.

Biomaterials with the hydroxyapatite and biopolymers such as chitosan derived of crustaceans are is an alternative for bone repair. Carbon nanotubes have been a focus of interest because they can ameliorate the biomechanical properties of biomaterials. The objective of this study was to evaluate these materials in the repair of cranial defects in rats. The animals were divided in groups: without implant (G1), implanted with the chitosan/carbon nanotube membrane (G2), and chitosan/nanotube membrane mineralized with hydroxyapatite (G3). The animals were sacrificed 5 weeks after surgery and the skulls were removed for analysis of the defect area. The results showed absence of chronic inflammatory and little bone neoformation in the defect area of all groups. In G2 and G3 there was lack of reabsorption of the biomaterial that were encapsulated by connective tissue. In conclusion, the biomaterials were biocompatible, but their specific physicochemical properties did not indicate a considerable osteoregenerative capacity.

Observation and analysis of the interphase are essential for a detailed understanding of the global composite properties when nanofillers are incorporated as interfacial agents. Techniques such as atomic force microscopy and nano-indentation provide valuable information on interfacial properties associated with the viscoelastic behavior of each phase. However, when the morphology of this region is observed in detail, instrumental errors may regularly appear, decreasing the accuracy of measurements. In this work, the use of transmission electron microscopy (TEM) was explored to image the glass fiber-reinforced polymer GFRP interphase containing interfacial nanocellulose. TEM lamellas were prepared via a focused ion beam to observe the phases disposed within the composite arrangement. Energy dispersive X-ray spectroscopy was also performed to determine the elemental composition in each sample phase. Interphase sizes between 25 and 50 nm thick were found, highlighting the ability of this characteriza...

In this study, polyacrylonitrile (PAN) as a polymer host is added with varying contents of lithium bis(trifluoromethane)sulfonimide (LiTFSI) as source of lithium (Li+) ions to form polymer electrolyte (PE) films. Dimethylformamide (DMF) is employed as the solvent. The electrical and structural properties of the PAN-based electrolytes are investigated by electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The PE film containing 40 wt. % of LiTFSI is found to exhibit the best ambient conductivity of 2.54 × 10−4 S cm−1 and the lowest degree of crystallinity. Investigation by FTIR spectroscopy has shown that PAN⋯DMF and DMF⋯Li+ interactions have occurred in the PAN-DMF-LiTFSI complexes. From XRD analysis, the films are found to be more amorphous with increasing LiTFSI contents. An electrochromic device is fabricated in the configuration of glass|ITO|WO3|electrolyte|CeO2-TiO2|ITO|glass, and the cathodic coloration and anodic bleaching of WO3 are found to occur at around −1.25 V and −0.40 V, respectively.

Time domain NMR (TD-NMR) has been widely used on the analysis of liquids or liquid components in heterogeneous materials such as food, biological tissues, synthetic and bio polymers, oil-bearing rocks, biomasses and cement-based materials. The use of TD-NMR for studying solid and soft mater has been growing in number and variety of applications, mostly for organic systems where the detection of 1H signals is highly advantageous. However, the strong 1H-1H dipolar interactions in solids make the 1H FID to decay in the same order of the dead time of most commercially available NMR probe heads. Thus, solid echoes are often used for recovering signals from solid components. In this article we reinvestigate the time-reversal solid-echo pulse sequence proposed by Rhim and Kessemeier, seeking for optimal pulse power and timing conditions that maximize its efficiency on recovering 1H signals from rigid segments. We show that under these optimized conditions, which we denote as Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE), the experiment can be more efficient than its most popular counterparts Solid-Echo (SE) and mixed-Magic Sandwich Echoes (mixed-MSE). Our results also suggest that, despite the finite pulse power, with current probe technology the RK-ROSE experiment is potentially able to provide an accurate estimation of rigid components, without relying on an external calibration using multiple standard samples, as usually done in SFC analysis of the FID signal. At last, we demonstrate that RK-ROSE can be adapted as a simple filter to supress signals from mobile segments in heterogeneous materials.

The development of polymers with low toxicity and efficient gene delivery remains a significant barrier of nonviral gene therapy. Modification and tuning of chemical structures of carriers is an attractive strategy for efficient nucleic acid delivery. Here, polyplexes consisting of plasmid DNA (pDNA) and dodecylated or non-dodecylated polysuccinimide (PSI)-based polycations are designed, and their transfection ability into HeLa cells is investigated by green fluorescent protein (GFP) expressing cells quantification. All cationic polymers show lower cytotoxicity than those of branched polyethyleneimine (bPEI). PSI and bPEI-based polyplexes have comparable physicochemical properties such as size and charge. Interestingly, a strong interaction between dodecylated polycations and pDNA caused by the hydrophobic moiety is observed in dodecylated PSI derivatives. Moreover, the decrease of GFP expression is associated with lower dissociation of pDNA from polyplexes according to the heparin displacement assay. Besides, a hydrophobization of PSI cationic derivatives with dodecyl side chains can modulate the integrity of polyplexes by hydrophobic interactions, increasing the binding between the polymer and the DNA. These results provide useful information for designing polyplexes with lower toxicity and greater stability and transfection performance. This work was developed within the framework of National Institute of Science and Technology of Pharmaceutical Nanotechnology (INCT-Nanofarma), which is supported by "Fundacao de Amparo a Pesquisa do Estado de Sao Paulo" (FAPESP, Brazil, Grant #14/14/50928-2) and "Conselho Nacional de Pesquisa" (CNPQ, Brazil, Grant #465687/2014-8). M.H.K. was the recipient of a CAPES and DAAD scholarship. Technical support by University of Sao Paulo and Freie Universitat Berlin is acknowledged.

The use of polymer has been showing an increasing consumption in the industry for the production of several consumer goods, mainly for the manufacturing of disposable products that can involve the combination of polymers with other materials. Nowadays, the annual production of polymers in the world exceeds 300 million tons. The industrial processes for these materials lead to a wide production of post-industrial waste that are highly complex and challenging for mechanical recycling due to the difficulty in separation step of macro-contaminant for this kind of waste. In this sense, the aim of this current study was to research and develop an efficient separation process with low cost for recycling of post-industrial scraps generated from production of adhesive bandage, which consisted of multiple layer films containing polymers, copolymers and cellulose. The polymeric waste was submitted to the well-established process called hydro-pulping, which does not require the use of chemical additives, resulting in efficient separation of cellulose pulp, while the residual polymer has been submitted to the thermomechanical processing by extrusion and injection molding. The separation of the polymers from cellulose by hydro-pulping method was successful. Therefore, the mechanical recycling of adhesive bandage waste presents full conditions for practical use.

International audience; This review article focuses on supramolecular assemblies involving cucurbit[n]uril-based containers and viologen guests as key building elements. Cucurbit[n]urils (CB[n], n=5-10) are fascinating hosts forming a wide range of inclusion complexes (caviplexes) with 4,4'-bipyridinium salts, known as viologens, either as discrete 1:1 inclusion compounds with CB[7] or as ternary inclusion compounds involving two hosts or two guests (2:1) with CB[7], and (1:2 or 1:1:1) with CB[8]. This property is currently being actively exploited to design and prepare self-assembled dynamic stimuli-responsive supramolecular polymers including gels, vesicles, films and organized arrays of polymeric microspheres or nanoparticles. This reviews highlights the main benefits of such polymers and gives an overview of the achievements and progresses made in this field over the past decades .