Fe(II) Spin Crossover/Polymer Hybrid Materials: Investigation of the SCO Behavior via Temperature-Dependent Raman Spectroscopy,Physicochemical Characterization and Migration Release Study

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)₂}₂(abpt)₂] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials.     

Performance improvement of EPDM and EPDM/Silicone rubber composites using modified fumed silica,titanium dioxide and graphene additives

In this work, a polymeric composite was prepared from ethylene propylene diene monomer (EPDM) and silicone rubber (S) with additives of modified fumed silica (MFS), titanium dioxide (TiO₂) and graphene. The dielectric and thermal performances of the EPDM-based composites were studied. An increase in the dielectric constant and AC dielectric breakdown strength was observed for the EPDM rubber composites containing MFS, TiO_2, and graphene additives. In addition, the incorporation of the additives resulted7in a significant increase in the thermal stability (~30–50 °C) and thermal conductivity (~7–35%) of the composites. The combination of these various improvements gives suitable performance advantage to the polymeric composite for use in insulating applications.     

Organoinorganic composites based on tetraethoxysilane and nitrogen polybases

Hybrid organoinorganic composites insoluble in water and organic solvents were prepared by the hydrolysis of tetraethoxysilane in the presence of poly-1-vinylpyrazole, poly-1-vinylimidazole, and poly-4-vinylpyridine. The composition of the composites was determined by the nature of the polymeric nitrogen base and hydrolysis conditions. The composites synthesized showed high sorption activity in the extraction of the [PdCl₄]^2?, [PtCl₆]^2?, and [AuCl₄]^? ions from hydrochloric acid solutions.     

Poly(vinylidene fluoride)-γFe2O3 magnetic composites

Magnetic metal-polymer composites have been prepared by thermolysis of a metal carbonyl Fe(CO₅) in poly(vinylidene fluoride). These composites comprise ca. 100-Å-diam iron-oxide, γFe₂O₃, ferrimagnetic particles dispersed in the polymeric matrix. Small-angle x-ray studies show that these particles have a radius of gyration in the range 63–315 Å. The composites were prepared with up to ca. 20 wt % iron and were crosslinked, as evidenced by insolubility. Electron diffraction indicating the formation of some FeF₂ suggests metal-fluorine interaction during formation of the composite.     

Side chain liquid crystalline composites,occurrence of interdigitated bilayer smectic C phases

We report on the results of X-ray investigations in two series of polymer monomer composites, PM6Rm-33 and PMnR12-33, which consist of mixtures of achiral liquid crystalline side chain polymers and their monomers. These mixtures present a unique integration of monomer in the polymeric base which assists in modifying their properties and forming homogenous composites. X-ray measurements for all the investigated composites indicate the existence of bilayered smectic C phases (SmC₂). In several composites, the interlayer distance of the SmC₂ phase abnormally increases with cooling; this is associated with the aliphatic interdigitation at the tail-to-tail interface being more prominent when longer aliphatic tails are present.     

Assembled structures of nanocrystals in polymer/calcium carbonate thin-film composites formed by the cooperation of chitosan and poly(aspartate)

Assembled structures of calcium carbonate (CaCO₃) nanocrystals have been examined for polymer/CaCO₃ thin-film composites synthesized through a self-organization process inspired by biomineralization. For the crystallization of CaCO₃, a thin-film matrix of chitosan has been used as a polymeric substrate. When the matrix is immersed into a supersaturated aqueous solution of CaCO₃ containing 1.4 × 10⁻³ wt % poly(aspartate) (PAsp), thin-film crystals of CaCO₃ are formed spontaneously. Three kinds of disklike films have been observed under a polarizing optical microscope. Electron diffraction analyses of each film have revealed that one is aragonite, displaying radial orientation of the c axes, and the others are vaterite, exhibiting different orientations. Detailed observation by scanning electron microscopy has clarified that these films are assemblies of crystalline particles 10–20 nm in size. The thin-film composites have been obtained over a PAsp concentration range of 4.4 × 10⁻⁴ to 1.0 × 10⁻² wt %. Vaterite formation becomes dominant when the concentration of PAsp is increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5153–5160, 2006     

A new method of coating powdered supportswith conductive carbon films

A series of conductive composite materials were obtained by polymerization of acrylonitrile in water suspensions of Al₂O₃ powder followed by further carbonization of the polymeric films covering the Al₂O₃ grains. The electrical conductivity and activation energy of the composites were measured in relation to the parameters used in preparation of the samples. This highly effective procedure can be used to improve electrical conductivity of the cathodes in lithium ion batteries.     

Polymeric Carbon Nitride/Mesoporous Silica Composites as Catalyst Support for Au and Pt Nanoparticles

Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CN_x)/mesoporous silica (SBA‐15) composites, which were synthesized by thermal polycondensation of dicyandiamide‐impregnated preformed SBA‐15. By changing the condensation temperature, the degree of condensation and the loading of CN_x can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA‐15 support, coating of SBA‐15 with polymeric CN_x resulted in much smaller and better‐dispersed metal NPs. Furthermore, under catalytic conditions the CN_x coating helps to stabilize the metal NPs. However, metal NPs on CN_x/SBA‐15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CN_x support.     

New hybrid polyoxometalate/polymer composites for photodegradation of eosin dye

New polyoxometalate (POM)/polymer hybrid composites were prepared by photopolymerization under mild conditions for suitable photocatalytic processes. Polyoxometalates were incorporated in special photosensitive resins, which were photopolymerized under visible light to obtain new materials with photocatalytic activity for dye removal. The synthesized composites were characterized by real‐time FT‐IR, and the photocatalytic ability was investigated on Eosin‐Y removal using photolysis under near UV irradiation. Interestingly, the polyoxometalates keep their photocatalytic properties, while incorporated into the polymeric matrix since very high conversion rates of Eosin‐Y were achieved. Indeed, degradation efficiencies of about 98% and 93% were registered when using H₃PMo₁₂O₄₀/polymer and 94% for SiMo₁₂O₄₀(IPh₂)₄/polymer composites, respectively. These first results reported in this article show that the new synthesized POM/polymer composites could be considered as promising materials for green and more suitable organic dye removal from aqueous solutions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1538–1549     

Preparation of porous CaCO3/PAM composites by CO2 in water emulsion templating method

Emulsion templating is an effective method to prepare well-defined porous polymeric materials. In this paper, porous CaCO₃/polyacrylamide (PAM) composites were prepared by emulsion templating polymerization in supercritical CO₂(scCO₂) by using a commercial grade surfactant (FC4430), therefore, the amount of the fillers and the pore size distribution of the composites can be modulated based on the demands of those potential applications as biomaterials. Calcium carbonate crystals can be in situ synthesized in the porous PAM matrix, and the morphology of CaCO₃ varied with the conditions of the reaction, the results indicated that three kinds of crystals were observed in the porous matrix. The results of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) showed that the macropores in PAM were interconnected and with narrow pore size distributions.     

Effect of Polythiophene Content on Thermomechanical Properties of Electroconductive Composites

The thermal, mechanical and electrical properties of polymeric composites combined using polythiophene (PT) dopped by FeCl₃ and polyamide 6 (PA), in the aspect of conductive constructive elements for organic solar cells, depend on the molecular structure and morphology of materials as well as the method of preparing the species. This study was focused on disclosing the impact of the polythiophene content on properties of electrospun fibers. The elements for investigation were prepared using electrospinning applying two substrates. The study revealed the impact of the substrate on the conductive properties of composites. In this study composites exhibited good thermal stability, with T₅ values in the range of 230–268 °C that increased with increasing PT content. The prepared composites exhibited comparable PA T_g values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using Fourier Transform Infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM).     

Photoconductivity of C60‐doping benzocarbazole‐substituted polysiloxanes on an operating wavelength of 633 nm

A novel polysiloxane having benzo[a]carbazole, benzo[a,i]carbazole, and benzo[a,g]carbazole pendant groups has been synthesized and characterized. We studied the electric‐field‐induced xerographic properties, the photogeneration efficiency, and the photoconductivity of C₆₀‐doping polymeric composites at a wavelength of 633 nm. C₆₀‐doping with benzo[a,g]carbazole‐substituted polysiloxane shows a photogeneration efficiency of 56.55 × 10^?5 and a photoconductivity of 52.2 pS/cm at E = 100 V/µm, which was found to be higher than that of the other benzocarbazole‐substituted polysiloxane composites. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

Polyethylene (PE) composites with titanium oxide (TiO₂) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO₂ nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO₂). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO₂ and Mod‐TiO₂ nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO₂ nanocomposites containing 8 wt % of TiO₂ exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO₂ nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of Active Fillers on Properties of Heat-Resistant Composites

The effect of active fillers such as titanium nitrides TiN _x , carbides TiC _x , and carbonitrides TiC _x N _y (0.5 < x or x + y ≤ 1.0) on properties of polymeric composites based on thermostable binders PAIS-104, SFP-012 AK-30, and ED-20 is studied.     

Polymerization of aqueous formaldehyde induced by ionizing radiation

In this work we examined the formation of polymeric material from the radiation-induced reactions of aqueous formaldehyde. The polymers obtained by this procedure are very different from those formed by thermal or UV polymerization. Two polymeric materials precipitated between 0.8 and 1.3 MGy. Although these polymers have the same chemical composition (C₂H₃O), infrared spectrum, and NMR spectrum, they differ in density, color and melting point. The interconversion of the polymeric materials increase when the dose is raised.     

A Simple and Efficient Route to Prepare Inorganic Compound/Polymer Composites in Supercritical Fluids

Summary: A simple and efficient route to prepare inorganic compound/polymer composites in CO₂‐based supercritical solution is presented. By this method, using polymeric hollow spheres as a substrate and Eu(NO₃)₃ as precursor, Eu₂O₃/polymer composites are successfully fabricated via the decomposition of the precursor in a supercritical CO₂/ethanol mixture at 120 °C. The resulting composites are characterized by means of transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. It is indicated that besides being decorated on the outer surface of the polymer spheres, Eu₂O₃ nanoparticles are imbedded in the shell and further into the hollow cavity of the polymer spheres. The loading content and particle size of Eu₂O₃ on the polymer spheres can be controlled by changing the concentration of precursor in the solutions. The photoluminescence spectrum of the composites exhibit two peaks at 592 and 615 nm, which indicates that the composites can be used as optical material to emit red light. This method is also extended to the preparation of other inorganic compound/polymer composites with different functions.

Eu₂O₃ nanoparticles are decorated on the outer surface of the polymer spheres.     

Structure and properties of polymeric ethyne-hexacarbonyldicobalt π complexes

A polymeric ethyne-hexacarbonyldicobalt π complex was prepared by the reaction of poly-p-diethynylbenzene with Co₂(CO)₈. The conformations in which the polymer chains can exist and the conformations in which the ?C≡CH and-Ph-groups can form π complexes with Co₂(CO)₈ were revealed by analysis of Stuart-Briegleb molecular models. The IR spectra of the polymeric complexes were analyzed, and their thermal degradation in air was examined.     

Thermal degradation of Pb(Zr0.53Ti0.47 )O3/poly(vinylidene fluoride) composites as a function of ceramic grain size and concentration

Poly(vinylidene fluoride)/Pb(Zr_0.53Ti_0.47)O₃,([PVDF]_1?x/[PZT]_x) composites of volume fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powders with average grain sizes of 0.2, 0.84, and 2.35 μm in different volume fraction of PZT up to 40 % were mixed with the polymeric matrix. The influence of the inorganic particle size and its content on the thermal degradation properties of the composites was then investigated by means of thermo-gravimetric analysis. It is observed that filler size affects more than filler concentration the degradation temperature and activation energy of the polymer. In the same way and due to their larger specific area, smaller particles leave larger solid residuals after the polymer degradation. The polymer degradation mechanism is not significantly modified by the presence of the inorganic fillers. On the other hand, an inhibition effect occurs due to the presence of the fillers, affecting particularly the activation energy of the process.     

Preparation and electrochemical characterization of a polymer Li1.03Mn1.97O4/pEDOT composite electrode

The development and characterization of a polymeric composite based on non-stoichiometric Li_1.03Mn_1.97O₄ spinel operating at 4 V and poly(3,4-ethylenedioxy)thiophene (pEDOT) are reported. In this composite the pEDOT substitutes the carbon usually mixed with the inorganic oxide-based electrodes to improve their electronic conductivity; the pEDOT thus functions as an electronic conductor and is electroactive in the same potential range of LiMn₂O₄. Electrochemical data for pure pEDOT and for composites of pEDOT/carbon, conventional Li_1.03Mn_1.97O₄/carbon and polymer Li_1.03Mn_1.97O₄/pEDOT are reported and discussed.     

Silicate coatings on titanium, modified with transition metal oxides and their activity in CO oxidation

CuO+M _x O _y /TiO₂+SiO₂/Ti composites (M = Mn, Fe, Co, Ni) were produced by plasma-electrolytic oxidation and impregnation, followed by annealing. The elemental and phase composition of these composites were examined and their activity series in CO oxidation was determined.