Free-standing Transparent Films Research Articles

Development of Bio-Active Patches Based on Pectin for the Treatment of Ulcers and Wounds Using 3D-Bioprinting Technology.

Biodegradable 3D-printable inks based on pectin have been developed as a system for direct and indirect wound-dressing applications, suitable for 3D printing technologies. The 3D-printable inks formed free-standing transparent films upon drying, with the latter exhibiting fast disintegration upon contact with aqueous media. The antimicrobial and wound-healing activities of the inks have been successfully enhanced by the addition of particles, comprised of chitosan and cyclodextrin inclusion complexes with propolis extract. Response Surface Methodology (RSM) was applied for the optimization of the inks (extrusion-printing pressure, shrinkage minimization over-drying, increased water uptake and minimization of the disintegration of the dry patches upon contact with aqueous media). Particles comprised of chitosan and cyclodextrin/propolis extract inclusion complexes (CCP), bearing antimicrobial properties, were optimized and integrated with the produced inks. The bioprinted patches were assessed for their cytocompatibility, antimicrobial activity and in vitro wound-healing properties. These studies were complemented with ex vivo skin adhesion measurements, a relative surface hydrophobicity and opacity measurement, mechanical properties, visualization, and spectroscopic techniques. The in vitro wound-healing studies revealed that the 3D-bioprinted patches enhanced the in vitro wound-healing process, while the incorporation of CCP further enhanced wound-healing, as well as the antimicrobial activity of the patches.

Effect of organic solvent addition on electrochemical properties of ionic liquid based Na+ conducting gel electrolytes

A novel sodium ion conducting gel polymer electrolyte comprising room temperature ionic liquid, 1-ethyl 3-methyl imidazolium trifluoro-methane sulfonate (EMITf) incorporated with ethylene carbonate and propylene carbonate and its solution with sodium trifluoromethane sulfonate (NaTf) entrapped in poly(vinylidinefluoride-co-hexfluoropropylene) (PVdF-HFP) is prepared using solution cast technique. The gel electrolyte is obtained in the form of free-standing transparent film. The gel electrolyte offers electrical conductivity of ∼10−3Scm−1 at ∼30°C with good mechanical, thermal and electrochemical stability window. The electrical conductivity is measured as a function of temperature and found to be consistent with Vogel-Tamman-Fulcher (VTF) relationship in the temperature range from 30°C to 75°C.Sodium ion conduction in the gel electrolyte film is confirmed from cyclic voltammetry and transport number measurements. The value of the sodium ion transport number of the ionic liquid based gel electrolyte is ∼0.19. The sodium sulfur battery with the gel electrolytes delivers the first discharge capacity of 267mAhg−1 sulfur and then it decreases with repeated charge–discharge cycles.

Successful entrapment of carbon dots within flexible free-standing transparent mesoporous organic-inorganic silica hybrid films for photonic applications

The effective entrapment of Carbon dots (CDs) into a polymer-silica hybrid matrix, formed as free standing transparent flexible films, is presented. The composite's synthesis, characterization, device application and properties -mechanical, thermal and optical- are being provided and discussed. CDs of 3nm mean size with strong photoluminescence are embedded into a silica matrix during the sol-gel procedure, using tetraethyl orthosilicate as the precursor and F127 triblock copolymer as the structure directing agent under acidic conditions. The final hybrid nanostructure forms free standing transparent films that show high flexibility and long term stable CDs luminescence indicating the protective character of the hybrid matrix. It is crucial that the photoluminescence of the hybrid's CDs is not seriously affected after thermal treatment at 550°C for 30min. Moreover, the herein reported hybrid is demonstrated to be suitable for the fabrication of advanced photonic structures using soft lithography processes due to its low shrinkage and distortion upon drying, both attributable to its porosity. Finally, it is reported that addition of F127 ethanolic solution in aqueous solution of CDs induces a blue-shift of their photoluminescence.

Solid-state polymer nanocomposite electrolyte of TiO2/PEO/NaClO4 for sodium ion batteries

A free-standing transparent film for sodium-ion conduction in PEO-based solid polymer electrolyte (additionally comprising NaClO4 and nano-sized TiO2) has been fabricated for use in Na-ion batteries by using a solution casting technique. The crystallinity of the solid polymer electrolyte and the interactions between PEO and the Na-ions is characterized by X-ray diffraction (XRD) and Fourier transformed infra-red (FTIR) spectra, which reveals the degree of Na+ ion solvation by PEO oxygen atoms (EO:Na). The ionic conductivities of the films are investigated by impedance analysis from 1 MHz to 1 Hz within the temperature range 303–363 K. A solid polymer electrolyte with anatomic ratio EO:Na = 20 exhibits a maximum ionic conductivity of 1.35 × 10−4 S cm−1, which increases to 2.62 × 10−4 S cm−1 by the addition of TiO2 (3.4 nm, 5 wt%) at temperature 60 °C. The performance of a Na2/3Co2/3Mn1/3O2 half cell with a polymer electrolyte is compared to a similar cell with a liquid electrolyte.

Transparent and self-standing manganese zinc ferrite nanoparticle/cellulose hybrid films

Transparent cellulose-based hybrid nanocomposites comprising dispersed manganese zinc ferrite (MZF) nanoparticles were synthesized in situ from metal acetylacetonates at tempeartures below 100°C. The size of the spinel particles prepared in the presence of HPC was smaller than that obtained in the absence of HPC. The MZF nanoparticle/cellulose hybrids were confirmed to be superparamagnetic. A free-standing transparent film showed a blue-shifted absorption edge, which reflected the size of the MZF particles formed in HPC.

Free-standing, roll-able, and transparent silicone polymer film prepared by using nanoparticles as cross-linking agents

A free-standing, roll-able, and transparent silicone-based polymer film with a tensile modulus of ca. 7.8MPa and strain at the break point of 0.76% was successfully prepared by reaction between a reactive silicone oligomer with methyl- and methoxy-side groups and hydrophilic SiO2 nanoparticles. First, SiO2 nanoparticles were grafted with silicone chains by a controlled wet chemical sol–gel-type reaction with the reactive oligomers. The solvent of the resulting solution was evaporated to form a viscous suspension, casted into a film, and finally heat-treated at 100°C and 150°C. A hydrolysis and condensation reaction among silicone-grafted SiO2 nanoparticles and free silicone oligomers in the final heat treatment resulted to produce free-standing, roll-able, and transparent silicone-based polymer film. The fact that the silicone film cannot be synthesized without the presence of SiO2 nanoparticles suggests that these nanoparticles act as cross-linking agents of silicone components providing the improved mechanical properties to the composite film. The rate-controlled mixing and heating of the SiO2 aqueous/alcohol suspension and the silicone oligomer/alcohol solution was found to be the key step in the synthesis of the free-standing transparent film. While rapid addition/mixing resulted in a fragile and opaque film, a transparent material was achieved when those solutions were slowly mixed. The effect of the synthesis process on the macroscopic and microscopic properties of the prepared films is discussed along with their formation mechanism.

Ion transport and ion–filler-polymer interaction in poly(methyl methacrylate)-based, sodium ion conducting, gel polymer electrolytes dispersed with silica nanoparticles

Experimental studies are carried out on novel sodium ion conducting, gel polymer electrolyte nanocomposites based on poly(methyl methacrylate) (PMMA) and dispersed with silica nanoparticles. The nanocomposites are obtained in the form of free-standing transparent films. A gel electrolyte with ∼4 wt.% SiO 2 offers the maximum electrical conductivity of ∼3.4 × 10 −3 S cm −1 at ∼20 °C with good mechanical, thermal and electrochemical stability. Physical characterization by X-ray diffraction, Fourier transformed infra-red and scanning electron microscopy is performed to examine ion/filler-polymer interaction and the possible changes in the texture of the host polymer due to liquid electrolyte entrapment and the dispersion of SiO 2 nanoparticles. The temperature dependence of the electrical conductivity is consistent with an Arrhenius-type relationship in the temperature range from 25 to 75 °C. Sodium ion conduction in the gel electrolyte film is confirmed from cyclic voltammetry and transport number measurements. The value of the sodium ion transport number ( t N a + ) of the undispersed gel electrolyte is ∼0.23 and it is almost unaffected due to the dispersion of SiO 2 nanoparticles. The effect of SiO 2 dispersion on ionic conduction is described in terms of anion–filler surface interaction.

Synthesis of Free-Standing Crystalline Barium Titanate Films at Vapor/Liquid or Liquid/Liquid Interface

Synthesis of free-standing crystalline barium titanate (BaTiO3) films at vapor/liquid or liquid/liquid interface at room temperature has been investigated. High concentration Ba, Ti alkoxides precursor solution (1.2 mol/l) or pre-hydrolyzed precursor solutions by water vapor in a H2O/Ba molar ratio of 0 to 6 were used as dropping solutions at the interfaces. Transparent gel films were formed when partially hydrolyzed precursors (H2O/Ba = 2 to 3) were spread out on a N2/liquid paraffin interface. The films shrank from syneresis and vaporization of the solvent during aging at room temperature. As a result, free-standing transparent films with a thickness of around 1 μm and little stoichiometric deviation were obtained by separation from the liquid surface and rinse by hexane. The films consisted of crystalline BaTiO3 particles of less than a few nanometers. Nanostructured dense BaTiO3 free-standing films with a grain size less than 100 nm were obtained at 1030°C.