Literatura científica selecionada sobre o tema "Fluorinated Soft-Matter"

Abstract Hydroxyl-containing fluoroacrylate copolymers with different fluorine and hydroxyl concentrations were synthesized via free-radical solution polymerization. Transparent fluorinated polyurethane (FPU) films were prepared by curing the copolymers with HDI (hexamethylene diisocyanate) trimer. The Fourier transform infrared spectroscopy (FT-IR) results revealed introduction of fluorine both into the copolymer and polyurethane. X-ray photoelectron spectroscopy (XPS) analyses indicated that a gradient concentration of fluorine existed in the depth profile of the fluorinated polyurethane films. The highest contact angle (CA) was obtained for the FPU film with fluoroacrylate monomer concentration of 22 wt.% because of fluorine present on the film surface. The surface topographies detected by SEM and AFM indicated that surface roughness contributed little to the film hydrophobicity. By increasing the fluoroacrylate monomer concentration, the decreasing of crosslinking degree of hard segment resulted in lowering the first degradation temperature, while more C-F groups in soft segment led to higher second degradation temperature. UV-Vis spectrophotometer measurements indicated that the FPU film with the fluoroacrylate monomer concentration of 16 wt.% still had a high transmittance of more than 90 % in the whole visible wavelength range.

Abstract The activity of photosensitizing systems based on water-soluble photoditazine (PDZ) and hydrophobic fluorinated tetraphenylporphyrin (TPPF20) solubilized polyvinylpyrrolidone (PVP) (in the case PDZ) and pluronic F127 (in the case TPPF20) was studied in a model reaction of tryptophan (Trp) photooxidation. We also studied the effect of dinitrosyl iron complex (DNIC) and sodium alginate (SA) polysaccharide on the photosensitizing activity of both PDZ in the presence of PVP and TPPF20 solubilized with pluronic F127 in a model reaction of Trp photooxidation. It was shown that TPPF20 solubilized with pluronic F127 exhibits high photocatalytic activity in the presence of both DNIC and SA. It was also shown that PVP is able to prevent the damaging effect exerted by active NO radicals produced during the photodecomposition of DNIC on PDZ molecules. Moreover, it was demonstrated that SA does not influence the photocatalytic activity of PDZ in the presence and absence of PVP. Using the dynamic light scattering method, it was found that SA macromolecules in the presence of PVP are capable of self-association, which, due to the ‘excluded volume’ effect, can cause a slight increase in the rate of photocatalytic reaction. The effectiveness of using PDZ in combination with PVP in the presence of SA and DNIC as a photosensitizer in antimicrobial photodynamic therapy was studied via in vivo experiments on a model of a full-layer planar wound in laboratory rats. Morphological studies have shown that under photodynamic action on wounds, the use of these systems (compared to photoexcitation of an aqueous solution of the initial PDZ) stimulates the transition of the inflammatory phase to the reparative (proliferative) phase. In addition, the process of cleansing wounds from microflora and devitalized tissues is accelerated, the disturbed microcirculation is restored, the proliferation of fibroblasts and blood vessels, and collagen synthesis are accelerated. It is suggested that the PDZ-PVP-SA-DNIC systems can be used in PDT procedures for the treatment of inflammatory diseases of the skin and soft tissues.

Abstract Piezo/ferroelectrets are a kind of cellular electret materials exhibiting piezoelectric effect. Owing to their large piezoelectric activity, flexibility, lightweight, low cost and large area, a list of promising applications have been suggested, including wearable sensors, actuators, micro energy harvesters, and etc. In terms of actual application, one of the most important performance indexes is the stability of piezoelectric response in complex application environments. This article mainly focuses on the influence of soft X-ray and ultraviolet irradiations on piezoelectric sensitivity of two kinds of sensors, made with irradiation cross-linked polypropylene (IXPP) and air-filled parallel-tunnel fluorinated ethylene propylene (FEP) piezoelectret films. A versatile encapsulation process with silica gel for sensor fabrication was introduced to improve the stability against radiations. The results show that soft X-ray irradiation can accelerate the depolarization of the piezoelectrets, while the influence of ultraviolet irradiation on piezoelectrets is not prominent. Encapsulation of the sensors with silica gel may significantly improve their stability under the radiation of soft X-ray. As indicated, the piezoelectric sensitivities of the encapsulated samples, made with IXPP and parallel-tunnel FEP piezoelectret films, are 50.2% and 6.9% of the initial values after 150 min irradiation of soft X-ray with an energy of 9.5 keV, respectively.

AbstractHigh temperature dielectric polymers are the favored materials for energy storage devices under harsh‐environment, e.g., electronic devices and power systems. It is widely acknowledged that the energy storage capabilities of dielectric polymers are markedly deteriorated at elevated temperature because of the exponential increased leakage current. Herein, all‐organic dielectric polymer alloys with two‐phase continuous hard‐soft structure have been firstly investigated via blending high glass transition temperature (Tg) fluorinated polyimide (FPI) and high bandgap aliphatic polyimide (API). The large energy band difference between FPI and API is conducive to trap energy and greatly inhibits conduction loss. In addition, the hard and soft molecular chains with two‐phase interlocking structures are more closely arranged, bringing torturous pathways for charge carriers and reducing free volume, which enhances the breakdown strength. FPI/API alloy with high Tg (296 °C) and concurrent large bandgap delivers an ultrahigh discharge energy density of 6.6 J cm−3 at 150 °C and 3.02 J cm−3 at 200 °C with 90% discharge efficiency, significantly surpassing those reported dielectrics. Moreover, the FPI/API alloy exhibits remarkable cyclability and dielectric stability up to 10000 charge‐discharge cycles even at elevated temperatures. This work provides an unprecedented opportunity on structure design of dielectric polymers to achieve high‐temperature energy storage capacitors.

Machine learning has recently been introduced in the context of droplet microfluidics to simplify the process of droplet formation, which is usually controlled by a variety of parameters. However, the studies introduced so far have mainly focused on droplet size control using water and mineral oil in microfluidic devices fabricated using soft lithography or rapid prototyping. This approach negated the applicability of machine learning results to other types of fluids more relevant to biomedical applications, while also preventing users that do not have access to microfluidic fabrication facilities to take advantage of previous findings. There are a number of different algorithms that could be used as part of a data driven approach, and no clear comparison has been previously offered among multiple machine learning architectures with respect to the predictions of flow rate values and generation rate. We here employed machine learning to predict the experimental parameters required for droplet generation in three commercialized microfluidic flow-focusing devices using phosphate buffer saline and biocompatible fluorinated oil as dispersed and continuous liquid phases, respectively. We compared three different machine learning architectures and established the one leading to more accurate predictions. We also compared the predictions with a new set of experiments performed at a different day to account for experimental variability. Finally, we provided a proof of concept related to algae encapsulation and designed a simple app that can be used to generate accurate predictions for a given droplet size and generation rate across the three commercial devices.

Les perfluoroalkylalcanes (PFAA ; CnF2n+1CmH2m+1 ; FnHm) sont des molécules diblocs formées par des blocs hydrogénés (CH) et perfluorés (CF). Les deux sont hydrophobes et mutuellement phobiques. Bien qu'ils ne possèdent pas de groupe polaire, ces tensioactifs primitifs forment des films de Langmuir sur l'eau ou des substrats hydrophiles. Les films comprennent des hémimicelles monodispersées bien définies, ordonnées de manière hexagonale, comme le montrent les expériences de microscopie à force atomique (AFM) et de diffraction des rayons X à incidence rasante. Il a été observé que le diamètre de ces hémimicelles est lié à la structure moléculaire. Cependant, les effets de la structure moléculaire variable (n et/ou m), du mélange dans des films binaires et des propriétés physicochimiques de la sous-phase liquide sur la structure et l'ordre des films de Langmuir restent encore inexploités.Des études numériques préalables (simulation de dynamique moléculaire (MD)) ont élucidé la structure interne des hémimicelles F8H16 pures. Ici, les hémimicelles FnHm ont également été étudiées par MD en fonction de n et m. Il a été constaté que la disposition en éventail des molécules au sein des hémimicelles explique la variation du diamètre de l'hémimicelle avec l'architecture moléculaire, en particulier l'inadéquation des sections transversales des chaînes CH et CF et les longueurs relatives des chaînes CH. et chaînes CF. Un modèle basé sur des arguments géométriques est proposé. En outre, il a été constaté que la fosse centrale des hémimicelles mise en évidence par les mesures AFM résulte à la fois de l'interaction intermoléculaire des dipôles CH2-CF2 et de la capacité à déformer le substrat liquide. Enfin, il a été constaté que la formation d'hémimicelles ordonnées de FnHm est possible sur d'autres sous-phases liquides telles que les alcools CH et CF à chaîne courte.En outre, la structure et l'ordre des films de Langmuir mixtes F8H14: F8H20 ont été sondés par des isothermes de pression de surface et de surface moléculaire, la diffusion des rayons X aux petits angles à incidence rasante (GISAXS) et la diffraction des rayons X à incidence rasante (GIXD). Il a été constaté que le paramètre de réseau du réseau d'hémimicelles se situe entre celui des cas purs. Ceci indique soit un mélange au niveau moléculaire (formation d'hémimicelles monodispersées mixtes) soit un mélange de deux types d'hémimicelles FnHm pures.Ces résultats sont prometteurs et mettent en lumière les principes fondamentaux qui régissent l'auto-assemblage et, à terme, la prédiction et le contrôle de la morphologie des films de Langmuir nanostructurés des PFAA, envisageant leur utilisation comme modèles pour les applications de nanostructuration de surface et de nanotechnologie. Les travaux futurs devraient se concentrer sur une caractérisation plus approfondie des films binaires mixtes, y compris avec différents n et m, afin de discerner les scénarios proposés. De plus, en s'appuyant sur les connaissances accumulées, les études devraient progresser vers l'étude de films et d'émulsions mixtes de PFAA avec des biomolécules pertinentes (par exemple les phospholipides)
Perfluoroalkylalkanes (PFAAs; CnF2n+1CmH2m+1; FnHm) are diblock molecules formed by a hydrogenated (CH) and a perfluorinated (CF) blocks. Both are hydrophobic and mutually phobic. Despite lacking a polar group, these primitive surfactants form Langmuir films on water or hydrophilic substrates. The films comprise well-defined, hexagonally ordered, monodispersed hemimicelles as shown by Atomic Force Microscopy (AFM) and Grazing Incidence X-rays Diffraction experiments. It has been observed that the diameter of these hemimicelles is linked to the molecular structure. However, the effects of varying molecular structure (n and/or m), mixing in binary films and the physicochemical properties of the liquid subphase on the structure and ordering of the Langmuir films are still left untapped.Computational (Molecular Dynamics (MD) simulation) studies have elucidated the internal structure of pure F8H16 hemimicelles. Herein, FnHm hemimicelles were also studied by MD as functions of n and m. It was found that the fan-like arrangement of the molecules within the hemimicelles explains the variation of the diameter of the hemimicelle with the molecular architecture, specifically the mismatch of the CH and CF chains' cross-sectional areas and the relative lengths of the CH and CF chains. A model based on geometrical arguments is proposed. Furthermore, it was found that the central pit of the hemimicelles evidenced by AFM measurements results from both the CH2-CF2 dipoles intermolecular interaction and the ability to deform the liquid substrate. Finally, it was found that the formation of ordered hemimicelles of FnHm is possible on other liquid subphases such as short-chain CH and CF alcohols.Further, the structure and order of mixed F8H14:F8H20 Langmuir films were probed by surface pressure-molecular area isotherms, Grazing Incidence Small Angle X-Ray Scattering (GISAXS) and Grazing Incidence X-Ray Diffraction (GIXD). It was found that the lattice parameter of the network of hemimicelles is between the ones of the pure cases. This indicates either a mixing at the molecular level (formation of mixed monodisperse hemimicelles) or a mixture of two types of pure FnHm hemimicelles.These results are promising and shed light on the fundamental principles driving the self-assembling and, ultimately, the prediction and control of the morphology of the nanostructured Langmuir films of PFAAs, envisaging their use as templates for surface nanopatterning and nanotechnology applications. Future work should focus on further characterising the mixed binary films, including with different n and m, to discern between the proposed scenarios. Moreover, drawing on the accumulated knowledge, the studies should advance towards studying mixed films and emulsions of PFAAs with relevant biomolecules (e.g. phospholipids)