Jana Kovářová

Synthesis and structural study of polypyrroles prepared in the presence of surfactants

Abstract Conducting and stable polypyrrole (PPy) was synthesized by chemical oxidative polymerization of pyrrole in aqueous solution containing an oxidant, ferric sulfate, and a surfactant. Anionic surfactants: sodium dodecylbenzenesulfonate, dodecylbenzenesulfonic acid, sodium dodecyl sulfate, poly(ethylene oxide)- n -alkyl-3-sulfopropyl ether potassium salt; cationic surfactant: tetradecyltrimethylammonium bromide; and non-ionic surfactants: poly(ethylene oxide) (10) iso- octylphenyl ether (Triton ® X-100), poly(ethylene oxide) (20) sorbitan monolaurate (Tween ® 20) and poly(ethylene oxide) (20) sorbitan monostearate (Tween ® 60) were used as additives. Results of the elemental analysis and FTIR spectroscopy proved that only the anionic surfactants were incorporated into PPy similarly as the doping anion. This leads to a better stability towards the deprotonation. Also thermal stability, checked by TGA in air, was improved. Scanning electron microscopy studies showed that the presence of the anionic surfactant strongly influenced the morphology of the polymer product.

Microdomain structure in polylactide-block-poly(ethylene oxide) copolymer films

Structured surface is an important property of polymer biomaterials for tissue engineering, for its capacity to expose domains with different surface energy and functional groups. For this purpose, amphiphilic A-B-A block copolymers with polylactide (PLA) as A blocks and poly(ethylene oxide) (PEO 3, Mn = 3090; PEO6, Mn = 6110) as B block were synthesized by ring-opening polymerization of either L-lactide (L-LA) or DL-lactide (DL-LA), using poly(ethylene glycol)s as macroinitiators and tin(II) octanoate (Sn(Oct)2) as a catalyst. Differential scanning calorimetry (DSC) and electron microscopy were used to study the phase separation of the hydrophobic (PLA) and hydrophilic (PEO) segments in films made of the copolymers and their blends with high-molecular-weight PLA homopolymers. Hydrophilic (PEO) and hydrophobic (PLA) domains were formed at the polymer film surface due to the separation of phases. The phase separation was affected by the copolymer composition and the stereoregularity of PLA blocks in the copolymers.

Polyaniline-coated cellulose fibers decorated with silver nanoparticles

Cellulose fibers of 20 μm in diameter and aspect ratio of 2 or 10 were coated with protonated polyaniline (PANI) during the oxidation of aniline hydrochloride with ammonium peroxydisulfate in an aqueous medium. The presence of PANI has been proved by FTIR spectroscopy. The conductivity increased from 4.0 × 10−14 S cm−1 to 0.41 S cm−1 after coating the fibers with PANI. The percolation threshold in the mixture of original uncoated and PANI-coated fibers was reduced from 10 mass % PANI to 6 mass % PANI, as the aspect ratio changed from 2 to 10. The subsequent reaction with silver nitrate results in the decoration of PANI-coated cellulose fibers with silver nanoparticles of about 50 nm average size. The content of silver of up to 10.6 mass % was determined as a residue in thermogravimetric analysis. FTIR spectra suggest that the protonated emeraldine coating changed to the pernigraniline form during the latter process and, consequently, the conductivity of the composite was reduced to 4.1 × 10−4 S cm−1, despite the presence of silver.

Biological and physicochemical study of zinc(II) propionate complexes with N-donor heterocyclic ligands

New zinc(II) propionate complexes (CH3CH2COO)2Zn·Ln·xH2O, where n=1-2, x=0 or 2, were prepared by reaction of zinc(II) propionate with heterocyclic ligands (L=theophylline, nicotinamide, methyl-3-pyridyl carbamate) and their thermal properties were studied. The prepared complex compounds were characterized by elemental analysis and IR spectra. TG/DTG and DTA measurements of the prepared compounds were performed in the air atmosphere under dynamic conditions. The thermal decomposition can be characterized as a multi-step process. The first step is attributed to the elimination of water or N-donor ligand molecules. It is followed by the decomposition of propionate anion when diethyl ketone and carbon dioxide were released. Zinc oxide was found as a final product of the thermal decomposition of the complex compounds under study. The volatile intermediate products of the thermal decomposition of zinc(II) propionate complexes were identified by IR-spectroscopy, qualitative chemical analyses and final solid product by X-ray powder diffraction method. Moreover, IR spectra suggest monodentate coordination of propionate anion to zinc. The complexes were tested against bacteria and filamentous fungi and show both antimicrobial activity and fungistatic effect towards pathogens as well as probiotic activity towards Lactobacillus paracasei.

The effects of controlled aging and blending of low- and high-density polyethylenes, polypropylene and polystyrene on their thermal degradation studied by pyrolysis gas chromatography

Abstract The effects of controlled thermal aging (oven-aging at 100°C in air), blending and compatibilization of high and low-density polyethylenes (HDPE and LDPE), polypropylene (PP) and polystyrene (PS) on the composition of the pyrolysis products were studied. No qualitative changes in the pyrolysis products were found due to the polymer aging or compatibilization. However, it was found that the relative amount of the pyrolysis products of LDPE and PS and of the blends, LDPE/PP and HDPE/PS, was influenced by the thermal aging, while in the case of well stabilized HDPE and PP homopolymers, no effect of the aging process on thermal degradation was observed. Moreover, the relative amount of pyrolysis products of polymer blends (LDPE/PP and HDPE/PS) was found to be exponentially dependent on their composition. The process of reactive compatibilization increased thermal stability of blended polymers and, consequently, the abundance of pyrolysis products was also changed.

Lifetime prediction of ABS polymers based on thermoanalytical data

The service life of ABS polymer, stabilized by 2-(3,5-di-tert-butyl-4-hydroxyanilino)-4,6-bis(octylthio)-1,3,5-triazine and containing 50% of a modifying rubber component, was estimated from oxidative induction times measured by DSC in isothermal mode in the temperature interval 140–170°C. The lifetime of ABS powder at the actual temperature of drying was predicted by linear extrapolation according to Arrhenius. However, the extrapolated value was much longer than the real lifetime determined from the long-term oven aging tests at 70 and 90°C, simulating the industrial drying process. The effect of changes in the apparent activation energy of oxidation due to antioxidant consumption during polymer aging is discussed.

Immunomagnetic sulfonated hypercrosslinked polystyrene microspheres for electrochemical detection of proteins

Poly(styrene-co-divinylbenzene) microspheres of narrow size distribution were prepared by (2-hydroxypropyl)cellulose-stabilized dispersion copolymerization of styrene and divinylbenzene in a 2-methoxyethanol/ethanol mixture under continuous addition of divinylbenzene. The copolymerization was initiated with dibenzoyl peroxide. The obtained microspheres were chloromethylated using several chloromethylation agents and then hypercrosslinked. Their porous structure was analyzed by nitrogen adsorption and mercury porosimetry. Superparamagnetic iron oxide nanoparticles were precipitated within the pores of microspheres from Fe(II) and Fe(III) chloride solution. The Fe content in the microspheres was determined by carbon analysis, atomic absorption spectroscopy and thermogravimetric analysis. Magnetic properties of the microspheres were characterized by magnetization curves and the temperature dependence of magnetic susceptibility. Finally, sulfo groups were introduced into the microspheres to prepare an immunomagnetic electrochemical biosensor for protein detection with ovalbumin as a model substance.

Multi-wall carbon nanotubes with nitrogen-containing carbon coating

Polyaniline coating was deposited on the surface of multi-wall carbon nanotubes of Russian and Taiwanese origin in situ during the polymerization of aniline. The deposited polyaniline film was subsequently carbonized under an inert atmosphere at various temperatures to produce coaxial coating of the carbon nanotubes with nitrogen-containing carbon. The new materials were investigated by infrared and Raman spectroscopies, which demonstrated the conversion of the polyaniline coating to a carbonized structure. X-ray photoelectron spectroscopy proved that the carbonized overlayer contains nitrogen atoms in various covalent bonding states. Transmission electron microscopy confirmed the coaxial structure of the composites. The Brunauer-Emmett-Teller method was used to estimate the specific surface area, the highest being 272 m2 g−1. The conductivity of 0.9–16 S cm−1 was measured by the four-point method, and it was only a little affected by the carbonization of the polyaniline coating.

Thermal behaviour and antimicrobial assay of some new zinc(II) 2-aminobenzoate complex compounds with bioactive ligands

New zinc(II) 2-aminobenzoate complexes with general formula Zn(2-NH2benz)2(L)2 (where 2-NH2benz is 2-aminobenzoate, and L is phenazone, N-methylnicotinamide, nicotinamide and isonicotinamide) were prepared and characterized by elemental analysis and by FTIR spectroscopy. The stability and thermal behaviour of the compounds were studied by thermal analysis techniques (TG/DTG, DTA), and the decomposition reactions were proposed. The decomposition of the studied compounds is always a multistep process, when after the release of the bioactive ligand, 2-aminobenzenecarbaldehyde, 2-aminobenzene and carbon dioxide were evolved. The solid intermediate compounds were confirmed by FTIR spectroscopy, and the volatile products were identified by mass spectrometry. The final solid product of thermal decompositions was zinc oxide, which was confirmed by XRD and FTIR analysis. The non-isothermal kinetic investigation of Zn(2-NH2benz)2(mnad)2 decomposition in air was performed by means of isoconversional methods, for a better understanding of the undergoing processes. The antimicrobial assay was carried out comparatively for the investigated compounds; they have higher biological activity towards Staphylococcus aureus, Escherichia coli and Candida albicans in comparison with zinc(II) 4-bromobenzoates.

Dip TIPS as a facile and versatile method for fabrication of polymer foams with controlled shape, size and pore architecture for bioengineering applications.

The porous polymer foams act as a template for neotissuegenesis in tissue engineering, and, as a reservoir for cell transplants such as pancreatic islets while simultaneously providing a functional interface with the host body. The fabrication of foams with the controlled shape, size and pore structure is of prime importance in various bioengineering applications. To this end, here we demonstrate a thermally induced phase separation (TIPS) based facile process for the fabrication of polymer foams with a controlled architecture. The setup comprises of a metallic template bar (T), a metallic conducting block (C) and a non-metallic reservoir tube (R), connected in sequence T-C-R. The process hereinafter termed as Dip TIPS, involves the dipping of the T-bar into a polymer solution, followed by filling of the R-tube with a freezing mixture to induce the phase separation of a polymer solution in the immediate vicinity of T-bar; Subsequent free-drying or freeze-extraction steps produced the polymer foams. An easy exchange of the T-bar of a spherical or rectangular shape allowed the fabrication of tubular, open- capsular and flat-sheet shaped foams. A mere change in the quenching time produced the foams with a thickness ranging from hundreds of microns to several millimeters. And, the pore size was conveniently controlled by varying either the polymer concentration or the quenching temperature. Subsequent in vivo studies in brown Norway rats for 4-weeks demonstrated the guided cell infiltration and homogenous cell distribution through the polymer matrix, without any fibrous capsule and necrotic core. In conclusion, the results show the “Dip TIPS” as a facile and adaptable process for the fabrication of anisotropic channeled porous polymer foams of various shapes and sizes for potential applications in tissue engineering, cell transplantation and other related fields.