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Flame-resistant polymer composites were prepared based on polyvinyl alcohol (PVA) as a polymer matrix and a polyphosphonate as flame retardant. Oxalic acid was used as crosslinking agent. LiClO4, BaTiO3, and graphene oxide were also incorporated into PVA matrix to increase the ionic conductivity. The obtained film composites were investigated by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and microscale combustion tests. Incorporating fire retardant (PFRV), BaTiO3, and graphene oxide (GO) into a material results in increased resistance to fire when compared to the control sample. A thermogravimetric analysis revealed that, as a general trend, the presence of PFRV and BaTiO3 nanoparticles enhances the residue quantity at a temperature of 700 °C from 7.9 wt% to 23.6 wt%. Their dielectric properties were evaluated with Broad Band Dielectric Spectroscopy. The electrical conductivity of the samples was determined and discussed in relation to the LiClO4 content. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. Out of the various composites tested, the composite containing 35 wt% of LiClO4 exhibits the highest alternating current (AC) conductivity, with a measured value of 2.46 × 10−3 S/m. Taking into consideration all the aspects discussed, these improved composites are intended for utilization in the manufacturing of Li-Ion batteries.

The sustainable development of innovative eco-friendly multifunctional nanocomposites, possessing superior characteristics, is a noteworthy topic. Novel semi-interpenetrated nanocomposite films based on poly(vinyl alcohol) covalently and thermally crosslinked with oxalic acid (OA), reinforced with a novel organophosphorus flame retardant (PFR-4) derived from co-polycondensation in solution reaction of equimolar amounts of co-monomers, namely, bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)-(4-hydroxyaniline)-methylene)-1,4-phenylene, bisphenol S, and phenylphosphonic dichloride, in a molar ratio of 1:1:2, and additionally doped with silver-loaded zeolite L nanoparticles (ze-Ag), have been prepared by casting from solution technique. The morphology of the as prepared PVA-oxalic acid films and their semi-interpenetrated nanocomposites with PFR-4 and ze-Ag was investigated by scanning electron microscopy (SEM), while the homogeneous distribution of the organophosphorus compound and nanoparticles within the nanocomposite films has been introspected by means of energy dispersive X-ray spectroscopy (EDX). It was established that composites with a very low phosphorus content had noticeably improved flame retardancy. The peak of the heat release rate was reduced up to 55%, depending on the content of the flame-retardant additive and the doping ze-Ag nanoparticles introduced into the PVA/OA matrix. The ultimate tensile strength and elastic modulus increased significantly in the reinforced nanocomposites. Considerably increased antimicrobial activity was revealed in the case of the samples containing silver-loaded zeolite L nanoparticles.

The present study aimed to design macromolecular architectures having imide core in the main chain and bearing two 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide heterocycles in the side chain of each structural units as a synergetic two components key factor to induce attractive flame retardant properties in the resulted materials. The synthesis pathway consisted in the classical polycondensation reaction strategy using a phosphorus-containing diamine synthesized in the laboratory and three commercial dianhydrides co-monomers. The chemical structure confirmation of the phosphorus-containing polyimides has been performed by means of FTIR and NMR spectroscopy. The thermal stability of the products was introspected through TGA analysis. The char yields measured at 900oC ranged between 35% and 54%. Using these parameters limiting oxygen index values were theoretically calculated. Also, the microscale combustion calorimetry measurements have been conducted, in order to investigate the combustion mechanism of the synthesized phosphorus-containing polyimides.

In this study, hydrogels based on poly(vinylpyrrolidone) and chitosan, derived from different mixing ratios of poly(vinylpyrrolidone)/chitosan, were synthesized by the freeze-drying technique with the aim of obtaining new systems that could be used to release tetracycline hydrochloride (TH). Freeze-drying methods were also used to prepare the hydrogels containing TH. The hydrogels were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, as well as in terms of dynamic water vapour sorption capacity. The poly(vinylpyrrolidone)/chitosan hydrogels were evaluated with regard to the release of TH. The release profiles of TH from the poly(vinylpyrrolidone)/chitosan hydrogels depended on the chitosan content. It could be seen that if the concentration of chitosan was too high, the release was delayed and not fully achieved, because the release of the drug was prevented by the crystalline areas of the chitosan. According to the release study, the drug release mechanism of the poly(vinylpyrrolidone)/chitosan hydrogels loaded with TH perfectly fitted the Higuchi and the Korsmeyer-Peppas models. The highest value of water vapor sorption capacity was obtained for the hydrogel with the poly(vinylpyrrolidone)/chitosan ratio of 50/50. PVP-CS loaded with 3 wt% TH may potentially be used for the controlled delivery of tetracycline to treat oral infections.

Liquid crystalline hyperbranched poly(aryl ester)s (A2B3) were prepared by polycondensation reaction of 2-(6-oxido-6H-dibenzoxaphosphorin-6-yl)1,4-naphthalene diol with 1,3,5-benzenetricarbonyl trichloride, taken in two different molar ratios. The chemical structure of the newly synthesized hyperbranched polymers was confirmed by FTIR, 1H NMR, 13C NMR spectroscopy. The polymers exhibited high thermal stability with initial decomposition temperature above 410–435°C and char yield at 700°C higher than 40%. Combined differential scanning calorimetry, polarized optical microscopy and wide-angle X-ray diffraction measurements were carried out to closely examine their thermal behavior and phase transitions.

New fire-resistant thermosets are prepared based on a bisphenol A-epoxy resin which is thermally crosslinked in the presence of dicyandiamide and two phenols containing phosphorus atoms. The thermosets are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis (TGA), and microscale combustion calorimetry (MCC) tests. A nonisothermal kinetic study is performed based on processing of TGA data applying the method proposed by Vyazovkin. The lifetime prediction analyses establish that the phosphorus-containing polymers could be used at a constant temperature of 200°C up to 200–780 min. The MCC tests reveal an improvement of the flammability behavior, as well as a significant heat release capacity reduction for phosphorus-containing samples compared to the sample which has no phosphorus component.

Heat-resistant magnetic polymer composites were prepared by incorporating cerium-doped copper-nickel ferrite particles, having the general formula Ni1-xCuxFe1.92Ce0.08O4 (x: 0.0, 0.3, 0.6, 1.0), into a polyimide matrix. The effects of particle type and concentration on the thermal, magnetic, and electrical properties of the resulting composites were investigated. The samples were characterized by FTIR, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, differential scanning calorimetry, vibrating sample magnetometer, and broadband dielectric spectroscopy. The composites exhibited high thermal stability, having initial decomposition temperatures between 495 and 509 °C. Saturation magnetization (Ms), magnetic remanence (Mr), and coercivity (Hc) were found in range of 2.37–10.90 emu g−1, 0.45–2.84 emu g−1, and 32–244 Oe, respectively. The study of dielectric properties revealed dielectric constant values of 3.0–4.3 and low dielectric losses of 0.016–0.197 at room temperature and a frequency of 1 Hz.

A series of polyimides (PIs) was synthesized from 4,4′-diaminodiphenyl sulfide and various aromatic or aliphatic dianhydrides to obtain shielding layers for solar cells. Structural design strategy involved combination of alicyclic or fluorinated chemical sequences together with aromatic units and thioether bridges to optimize the balance between thermal stability, optical transparency and refractive index. Molecular modeling revealed significant differences in the spatial molecular conformations between PIs based on aromatic dianhydrides and those containing aliphatic ones. The transmittance spectra reflect the effects of electron-acceptability, polarizability and symmetry of dianhydride moiety, which contribute distinctly to charge transfer complex interactions. Light dispersion in the PI films allowed evaluation of optical reflection losses at interface with ZnO or ZnO:Sn. In terms of transparency and refraction characteristics, it was concluded that PIs derived from either aromatic sulfur-based dianhydride or non-symmetric cycloaliphatic dianhydride render the best features that match the demands for shielding layers in solar cells.

A study on thermal and thermo-oxidative stability, i.e. the degradation mechanism for a series of poly(arylene ether nitrile)s was performed by applying simultaneous mass spectrometry and Fourier transform infrared spectroscopy of gas products from a thermogravimetric analyzer into two working atmospheres, air and helium. The polymers were prepared by nucleophilic aromatic substitution of 2,6-dichlorobenzonitrile with phenolphthalein, 2,2-bis(4-hydroxyphenyl)propane and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole. A poly(arylene ether nitrile) was prepared by cyclopolycondensation reaction, in two steps, starting from 4,4′-oxydiphthalic anhydride and 2,6-bis(3-aminophenoxy)benzonitrile. The influence of benzonitrile units, isopropylidene linkages, phthalide groups, oxadiazole or imide rings on the thermal degradation behavior was discussed in detail. The onset mechanism of the thermal degradation process in the two working atmospheres was similar. The major identified products in the decomposition gases were carbon dioxide, water, carbon monoxide, benzene, phenol and benzonitrile. In addition, nitrogen monoxide was observed in the case of polymers containing oxadiazole or imide rings.

New composite cryogels for controlled release of Enalapril Maleate (EM) were developed based on two biodegradable polymers, poly(vinyl alcohol) (PVA) and pullulan (PU) as polymer matrix, and zeolite L (ZL) as inorganic filler. The cryogels were prepared by freeze-thaw technique using different concentrations of the components, the EM being introduced directly during the cryogel preparation. The samples were characterized by FTIR spectroscopy, scanning electron microscopy and water vapor sorption-desorption isotherms. The presence of PU and ZL in the cryogels led to the modification of FTIR characteristic absorption bands of EM and contributed to the modification of the cryogel morphology. The sample moisture absorption was in the range 5.28–18.20%, determined at a relative humidity RH = 82%. Cryogels based on PVA, PU and ZL components showed a longer EM release period compared to cryogels containing only PVA. The analysis of in vitro EM release kinetics was performed using three predictable models: zero and first order kinetics, and Korsmeyer-Peppas model. Korsmeyer-Peppas model best fitted the release data.

A new blue fluorescent aromatic diamine, 2-(4,4′-diamino-4″-triphenylamine)-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole, is synthesized in several steps. Based on this diamine four fluorescent imide-type polymers, a polyimide and three poly(amide-imide)s, are prepared by solution polycondensation reactions. The structures of the monomers and polymers are characterized by FTIR and NMR spectroscopy. The polymers show good solubility in organic solvents, and have high thermal stability, the decomposition temperature being above 380 °C, as is determined by TGA measurements. The thermal degradation mechanism of a polymer in an inert atmosphere is investigated by using the coupled TG/MS/FTIR technique. The optical properties are determined by UV-vis and fluorescence spectroscopy. The polymers exhibit strong absorption bands in the range of 357–373 nm, and blue fluorescence in solution within the range of 423–469 nm with low to moderate quantum fluorescence yields from 0.11 to 1.30% and Stokes shifts values of around 77 nm. The protonation is found to affect the spectral properties of the polymers.

This study presents the evaluation of thermal and thermo-oxidative stability of some polyimide-polydimethylsiloxane (PI-PDMS) copolymers and establishes the thermal degradation mechanism by simultaneous mass spectrometry and Fourier transform infrared spectroscopy of gas products from thermogravimetric analyzer (TG/MS/FTIR) in two working atmospheres: air and He. The thermal stability and the start mechanism of thermal degradation were correlated with the chemical structure of PI-PDMS and the working atmosphere. The main thermal decomposition products were determined in both oxidative and inert atmosphere.

Traditional materials are being constantly replaced by synthetic polymers, most of which are highly flammable. Epoxy resins are versatile and among the most important class of polymers, due to their multiple crosslinking capacity endowed by the oxirane ring, their applications ranging from adhesives to aeronautics. This study investigates the comparative effect of three hardeners (aromatic, cycloaliphatic, aliphatic) and the addition of an oligophosphonate on the thermal behavior and fire performance of bisphenol A diglycidyl ether semi–interpenetrating polymer networks. Networks with epoxy resin and 2% phosphorus loading were prepared. Evolved gases analyses, thermal and fire experiments were used to propose the action mode of the hardeners and oligophosphonate in the fire performance enhancement of the epoxy resin. Non–isothermal decomposition kinetics studies were conducted. The oligophosphonate in the epoxy resins promoted a significant reduction in the peak of heat release rate values (33 to 55%) in microscale combustion calorimeter experiments. A UL 94–V0 classification was achieved for the network with oligophosphonate and aromatic curing agent. The obtained results recommend the semi–interpenetrating network cured with aromatic hardener as a potential matrix for flame retardant composites or coatings.

In this paper, we have investigated the changes on the photophysical properties of two phenylquinoxalines in different chemical environments, such as in solvent mixtures (CHCl 3 /toluene and CHCl 3 /EtAc solvent mixtures) and in acidic media. The absorption and emission spectra of studied phenylquinoxaline derivatives were sensitive to composition of media. The spectral data were used to calculate different solvation parameters (i.e. the index of preferential solvation, δ S2 , the preferential solvation constant, K 12 , the preferential solvation parameters, f 2/1 , f 12/1 and f 12/2 ), the free energy of the reorientational interaction W m(g,e) and the solvation shell composition (the number of more polar solvent molecules involved in the first solvation shell (Nm)) according to various preferential solvation models. The fluorescence intensity in THF solution was gradually decreased upon increasing the HCl concentration, due to protonation of the nitrogen atoms.

New azomethines were synthesized by condensation reactions of salicylaldehyde with various aromatic amines containing 1,3,4-oxadiazole ring. A reference sample without the 1,3,4-oxadiazole ring was prepared using 1,3-bis(4-aminophenoxy)-benzene. The chemical structure was confirmed by FTIR and 1H NMR spectroscopy. The absorption and photoluminescence properties were investigated in tetrahydrofuran, acetonitrile, and N,N-dimethylformamide solutions. The obtained azomethines had absorption bands in the range of 240–420 nm and emitted violet and/or blue light located between 340 and 600 nm. In the DMF solution, one of the samples showed the excitation-wavelength dependent emission properties by shifting from ~ 382 to 442 nm. Furthermore, under basic conditions, the intensity of the main absorption band decreased and a new band appeared (at 420 nm), with a concomitant change of color from colorless to yellow. Finally, the spectral study of interactions of new azomethines with Cu2+, Co2+, Ag+, Ni2+, Sn2+, Zn2+ and Hg2+ revealed significant spectral changes and selectivity for Zn2+, Cu2+, Co2+ and Ag+ ions.

New hybrid films were prepared through a sol–gel process starting from a poly(ether ether ketone)-containing pendant carboxyl groups (PEEK-R) and various alkoxysilanes (tetraethoxysilane, methyltrietoxysilane, and phenyltriethoxysilane) as precursors of the inorganic network. PEEK-R was synthesized from 4,4′-difluorobenzophenone and a mixture of phenolphthalein and phenolphthalin. Owing to the presence of polar phthalide and carboxyl groups in the PEEK-R structure, the hybrid films showed homogeneous morphologies. The films exhibited good thermal stability, having initial decomposition temperature over 440°C and a glass transition of 180–218°C. The contact angle values of film surfaces with water and ethylene glycol increased by the introduction of silica. The dielectric spectroscopy analysis at lower temperature evidenced two secondary relaxation processes, γ and β. At higher temperature, a conductivity relaxation was observed. The thermal activation energy of conductivity was in the range of 0.6–1.02 eV, confirming the electronic conduction via hopping. Gas permeation tests using small molecules (He, N2, O2, and CO2) indicated that hybrid films showed higher permeability than pure polymer film for all tested gases. The permeability increase was accompanied by a slight reduction in selectivity, but CO2/N2 selectivity remained significantly high making this type of hybrid materials promising candidate for gas separation membranes. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

New aromatic polyazomethines were synthesized by polycondensation reaction of a diamine containing 1,3,4-oxadiazole ring, namely, 4,4′-diamino-4″-[2-(4-phenoxy)-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole)]triphenylmethane, with terephthalic aldehyde or bis(4-formylphenoxyphenyl)fluorene, by using N-methyl-2-pyrrolidinone (NMP) as solvent. The polymers were easily soluble in polar solvents, such as NMP, N, N-dimethylacetamide, or chloroform, and showed high thermal stability with the initial decomposition temperature above 415°C and the temperature of 10% weight loss in the range of 450–460°C. They exhibited high char yield at 800°C in the range of 52–56%. Optical properties were studied by absorption and photoluminescence spectra. In solution, the polymers presented two absorption maxima in the ranges 273–278 and 330–346 nm and emitted violet-blue light in the range of 413–468 nm, depending on the solvent polarity. The Stokes shift and emission quantum yield values depend on the polymer structure and solvent polarity. The emission intensity in NMP solution was enhanced upon increasing the HCl concentration, while the absorption spectral profile was slightly influenced.

The sensitivity and selectivity properties of three phenylquinoxaline derivatives to different metal ions were investigated by absorption and fluorescence spectroscopy. The absorption and fluorescence responses of the phenylquinoxaline derivatives were examined towards the following metal ions Ag+, Mg2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+, in THF solution. All investigated samples exhibit sensitivity and selectivity to Ag+, Co2+ and Cu2+ ions compared to other metal ions (Mn+ = Mg2+, Ni2+, Zn2+, Cd2+ and Hg2+). The gradual addition of Ag+, Co2+ and Cu2+ ions to a Q-Ox sample solution generates new absorption bands (with maxima at 244, 675 and 294 nm, in presence of the Ag+, Co2+ and Cu2+ ions, respectively) while the emission intensities were weakly quenched, except in presence of Ag+ ions, when the emission was almost completely quenched (quenching efficiency at 426 nm, (I0 − I) / I0 × 100% = 91%). Absorption and fluorescence results show the formation of 1:2 metal complexes with Ag+ ions and 1:1 stoichiometry for a complexation between Q-Ox and Co2+ or Cu2+ ions. The following characteristics of these phenylquinoxaline derivatives have been calculated and discussed: the effects of the interfering ions, the binding constants and the detection limit of Ag+, Co2+ and Cu2+ ions.

Flame retardation of poly (vinyl alcohol) with oligophosphonates, either as singular flame retardant filler or in the presence of intumescent additives, is a key to achieving eco-friendly advanced composites with improved reaction-to-fire properties. Herein, following a facile synthetic approach, PVA/oligophosphonate/ammonium sulfate composites were prepared via casting method. It was demonstrated that a low content of phosphorus led to composites exhibiting improved flame retardant properties. The peak heat release rate was substantially reduced in all the cases, depending on the content of oligophosphonates-based flame retardants or ammonium sulfate intumescent additive. Thermogravimetric data showed that the incorporation of the flame retardant significantly increased the phosphorus-rich char yield at elevated temperature.

New polymer nanocomposites with improved fire performance were developed based on polyvinyl alcohol (PVA) as polymer matrix, a polyphosphonate (PPH) and/or SiO2 nanoparticles. The structural and morphological properties of the resulting nanocomposites were investigated by Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM) and contact angle measurements. Thermal and combustion properties of the nanocomposites were determined by running thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and microscale combustion calorimetry (MCC) tests. The introduction of PPH and SiO2 nanoparticles increased the contact angle values, the glass transition temperature and the char yield at 800 °C. MCC tests revealed substantial improvement on the fire-resistant properties of the samples containing both PPH and SiO2, due to the synergistic effect. The total heat release decreased from 20.75 kJ/g, in pure PVA to 17.69 kJ/g in the sample containing 10% SiO2 and 10% PPH.

The photophysical characterization (absorption and emission spectra, fluorescence quantum yields, preferential solvation) of a polymer containing bisphenol A and 1,3,4-oxadiazole group (OxBisA) was studied in a wide variety of solvents. Influence of the medium characteristics on photophysical behavior was examined. The solvatochromic shifts of the spectral bands were analyzed by multiple parametric regression analysis in terms of solvent parameters of two new solvent scales (Catalan and new Laurence). Also, changes in the electronic emission spectral characteristics of OxBisA molecules were studied in chloroform solution in the presence of various amount of SnO2 and NiO oxide nanoparticles. The fluorescence intensity of polymer OxBisA gradually decreased with increases of oxide nanoparticles concentrations. The emission intensity of studied compound was sensitive to the compositions of the microheterogeneous media (involving different chloroform:methanol ratios).

Polyetherimide hybrid films containing 5–40% silica were prepared through a sol-gel process and thermal imidization by using methyltriethoxysilane as precursor of the inorganic network and a poly(amic acid) resulting from polycondensation reaction of 2,2-bis[4-(4-aminophenoxy)phenyl]propane with 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. The properties of these films, morphology, water vapor sorption capacity, free surface energy, mechanical, thermal and electrical characteristics, were studied. The films exhibited good thermal stability, having an initial decomposition temperature above 470 °C and glass transition temperature in the range of 187–200 °C. They showed low dielectric constant and low dielectric loss in a large frequency field. Gas permeation tests using small molecules (He, N2, O2 and CO2) at 6 bar and 30 °C indicated that the hybrid films containing higher silica content showed higher permeability for all the tested gases.

New poly(1,3,4-oxadiazole-imide)s were synthesized from a diamine containing 1,3,4-oxadiazole ring, 4,4′-diamino-4″-[(2-(4-phenoxy)-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole]triphenylmethane, and different aromatic dianhydrides: 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis[(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) and perylene-3,4,9,10-tetracarboxylic dianhydride. The polymers were easily soluble in polar organic solvents and exhibited high thermal stability, having 5% weight loss in the range of 445–470 °C and glass transition temperature in the domain of 201–244 °C. The optical properties were investigated in different media. The absorption characteristics (intensity, absorption maximum and shape) of investigated compounds depended on their chemical structures and the nature of environment. The emission of these samples was represented by one broadened and blue emission band. The largest and solvent dependent Stokes shifts values were obtained. The fluorescence quantum yield (QY) values of polymer with hexafluoroisopropylidene groups, in tetrahydrofuran solution, depended on the wavelength used for excitation. This is an exception from Kasha's rule and Vavilov's law, which was attributed either to photodecomposition or to the enhancement of intramolecular energy transfer process competing with internal conversion between singlet states. High QY values were obtained for polymers with isopropylidene or fluorene units in dimethyl sulfoxide (polar solvent), which may be due to the strong overlap of electronic transitions of species from system.

This study assesses the thermal and thermo-oxidative stability and establishes the degradation mechanism for five aromatic polyetherimides, by simultaneous mass spectrometry and Fourier transform infrared spectroscopy of off-gases from thermogravimetric analyzer in two working atmospheres: air and helium. Aromatic polyetherimides were synthesized starting from 4,4⿲-(4,4⿲-isopropylidenediphenoxy)bis(phthalic anhydride) and five aromatic diamines, three of them containing 1,3,4-oxadiazole ring. The study establishes the influence of the structure and of the working atmosphere on the thermal stability and the start mechanism of thermal degradation. Moreover, it determines the main decomposition products both in inert atmosphere (helium) and in air.

Advanced flame retardant epoxy resins, environmentally friendly, with different contents of a new oligophosphonate (PFR), were prepared using dicyandiamide as a hardener and 1,1-dimethyl-3-phenylurea as an accelerator. PFR, with a high phosphorus content, was synthesized by polycondensation reaction of phenylphosphonic dichloride with a phosphorus-containing bisphenol, namely bis((6-oxido-6H-dibenz[c,e][1,2]oxaphosphorinyl)-(4-hydroxyaniline)methylene)-1,4-phenylene. The bisphenol was prepared by reacting 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide with an imine bisphenol resulting from the condensation of 4-aminophenol with terephthalaldehyde. The structure and morphology of cured epoxy resins were evaluated by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) analysis, respectively. Differential scanning calorimetry analysis revealed that cured epoxy resins containing PFR possessed slightly higher glass transition temperatures than phosphorus-free cured epoxy resin. Thermogravimetric analysis and limiting oxygen index values indicated that the incorporation of PFR into epoxy resin substantially enhanced the thermal stability and flame retardancy of the char layer at high temperature. The surface morphology of the char residue was studied by SEM measurements. The kinetic processing of thermogravimetric data was carried out using Friedman and Vyazovkin methods. The lifetime prediction analysis established that the fire-resistant phosphorus-containing epoxy resins could be used at a constant temperature of 200 °C up to 620–630 minutes. The new PFR can be successfully used as a very efficient flame retardant for improving the fire-resistance properties of epoxy resins.

The photophysical properties of the three 1,3,4-oxadiazole derivatives containing fluorene (Ox-FL); fluorene and phenolphtaleine (Ox-FL-FF); or fluorene and bisphenol A (Ox-FL-BPA) moieties in the main chain were investigated by the fluorescence and absorption spectroscopy in different solvents and in the solid state. The electronic absorption spectra included a strong absorption band located in the 270–395 nm region, with a maxima around at 302 nm. The fluorescence excitation spectra were also characterized by one broad band, appearing in the wavelength range of 220–340 nm. All samples displayed the emission bands around 356–373 nm and exhibit high quantum yields ranged from 31.61 to 90.77%, in chloroform solution. The sensitivity of the emission spectra on medium characteristics (polarity, acidity and basicity) were evaluated by using the Catalan solvent scale and the fluorescence titration with a dilute acid solution.

Aromatic poly(ether-ether-ketone)s (PEEKs) have received much attention to be used in biomedical field, due to their good physicochemical properties, processability and biocompatibility. Metal-exchanged zeolites have demonstrated to be good biomaterials in various applications, because of their low-toxicity, functional groups for grafting and high dispersibility. In this study, new materials based on silver-containing zeolite L (Ag-ZL) and a PEEK containing phthalide units and pendant carboxylic groups were prepared. The films were characterized by FTIR spectroscopy, scanning electron microscopy and humidity absorption measurements. Their antimicrobial activity and cytotoxicity were investigated. The films having 12% Ag-ZL showed antimicrobial activity against Gram positive bacteria (Staphylococcus aureus 25923 ATCC and Staphylococcus aureus MRSA 43300 ATCC) and Gram negative bacteria (Escherichia coli 25922 ATCC) while those having 2% Ag-ZL were active only towards Gram positive bacteria. All the samples exhibited reduced cytotoxicity being thus potential candidates for biomedical applications.

Barium strontium titanate particles with composition of Ba0.5Sr0.4Ca0.1TiO3 were prepared by sol-gel method and doped with 1% Nb2O5. Poly(ether imide) composite films were obtained by mixing particles into a poly(amic acid) solution and casting onto glass plates followed by thermal treatment. The films were investigated by Fourier transform of infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and broadband dielectric spectroscopy. They exhibited good thermal stability having the initial decomposition temperature above 773 K. The dielectric constant was in the range of 3.08–4.17 (room temperature and 1 kHz), and the dielectric loss maintained low values over a large interval of frequency and temperature. The subglass transitions γ and β, the α-relaxation corresponding to the glass transition and the conductivity process of the composite films were evidenced and correlated with the particle content. The ability to generate electrical energy on mechanical impulse was also evaluated.

Polyimide composite films were prepared by casting solutions resulting from direct mixing of a poly(amic acid) and titanium dioxide (TiO2) nanotubes (TNTs) onto glass plates, followed by thermal imidization. TNTs with outer diameters of approximately 10–12 nm and length of several hundreds of nanometers were synthesized by the hydrothermal method. The morphology of the nanotubes was investigated by using high-resolution transmission electron microscopy. The influence of TNTs content on structural, thermal, and electromechanical properties of pure polyimide and composite films was studied. The scanning electron microscopy and atomic force microscopy showed good compatibility between TNTs filler and polyimide matrix. The value of average roughness of film surface increases with increasing the content of TNTs. The films were flexible, tough, and exhibited high thermal stability. A study of microelectromechanical properties of these films was performed. The films showed nanometric displacements in the range of 250–800 nm when an electric voltage of 500 V was applied on their surface.