Magdalena Hasik

FT-IR study of montmorillonite-chitosan nanocomposite materials.

Bone defect is one of the most frequent problems in bone tissue reconstruction in which application of a biomaterial filling is necessary. It creates a still rising demand of biomaterials for bone surgery. Polymer-ceramic nanocomposites (e.g. based on chitosan matrix) is a group of novel materials whose properties such as strength, Youngs modulus, bioactivity and controlled degradation time make them suitable materials for filling bone defects. Investigations of nanocomposite foils which consisted of biopolymer-chitosan (CS) matrix and montmorillonite (MMT) as a nano-filler was the subject of the work. The nanocomposite materials were produced by a two-step dispersion of the nanoparticles in the biopolymer matrix. The first stage involved mechanical stirring and the second one - ultrasonic agitation. Mechanical tests were performed on the nanocomposites and their Youngs modulus was estimated. Significant improvement of mechanical properties of the nanocomposites in comparison with the pure polymer (CS) was observed. The nanocomposite foils (CS/MMT) were subjected to FT-IR spectroscopy investigations whose objective was to explain the reason of the change in mechanical characteristics of the nanocomposites. Transmission and ATR techniques operating in MIR range were used to study the nanocomposites. The FT-IR techniques were used to determine interactions at nanoparticle-biopolymer matrix interface. A pure unmodified CS foil was used as a reference material for FT-IR studies. It was proven that application of FT-IR techniques allows not only to identify phases, but also to explain structural changes in the systems studied.

XPS studies of nitrogen-containing conjugated polymers–palladium systems

Polyaniline (PANI) and polypyrrole doped with chloride ions (PPyCl) have been treated with PdCl 2 solutions in HCl of various concentrations. Basing on the results of XPS studies it is shown that the differences in the redox and basic properties of both polymers lead to different mechanisms of their interactions with palladium ions present in the PdCl 2 solutions studied. Thus, in the PdCl 2 solutions of low acidity in which [PdCl 2 (H 2 O) 2 ] predominates, both polymers are oxidized with simultaneous reduction of a part of Pd 2+ to Pd 0 . In the PdCl 2 solutions of high acidity in which [PdCl 4 ] 2 is the major complex, reduction of Pd 2 does not occur. Owing to stronger basic properties of PANI than those of PPyCl, palladium is incorporated into the former polymer as anionic chlorocomplexes via protonation reaction. In the case of PPyCl the situation is more complex. Detailed analysis of the possible surface reactions taking place in the PPyCl Pd systems studied is given in the paper.

Polyaniline-coated silica gel

Abstract Silica gel microspheres 7 and 15 μm in diameter were coated with an overlayer of polyaniline camphorsulfonate or hydrochloride during the oxidative polymerization of aniline. Coated silica gel and polyaniline precipitate were separated using a difference in sedimentation rate. In an alternative approach, the microspheres were modified with polyaniline in the presence of 35 nm colloidal silica. This technique prevented the macroscopic precipitation of polyaniline. Coatings of neat, 3-aminopropyl- and octadecyl-modified silica gel with polyaniline hydrochloride were compared. The surface composition of coated microspheres was characterized by X-ray photoelectron spectroscopy. Potential applications of particles in electrorheology, organic catalysis, and in modeling of conductivity behavior in composites are demonstrated.

Polyaniline containing palladium — new conjugated polymer supported catalysts

Abstract Palladium can be incorporated into polyaniline (PANI) in the polyemeraldine base form via its treatment with PdCl 2 aqueous solutions containing various amounts of HCl. PANI is doped in all the cases, but the oxidation level of palladium introduced into the polymer matrix depends upon the acidity of the PdCl2 solution. After the reaction in highly acidic solutions Pd 2+ is exclusively present in the matrix, whereas upon PANI contact with the solutions of low acidity partial reduction of Pd 2+ to Pd 0 with simultaneous oxidation of the polymer takes place. PANI-Pd systems are active in the catalytic hydrogenation of 2-ethylanthraquinone. Their activity depends on preparation conditions.

Infrared and Raman studies of palladium—nitrogen-containing polymers interactions

In the present research the nature of interactions of poly(4-vinylpyridine) (PVP) and polyaniline (PANI) with various Pd 21 chlorocomplexes existing in PdCl2‐HCl‐H 2O solutions have been studied using IR (MIR, FIR) and Raman spectroscopies. It has been found that these interactions involve the nitrogen atoms of the polymers. In the PdCl 2 solutions of high HCl concentration containing [PdCl4] 22 and [PdCl3(H2O)] 2 as the major species acid‐base type reaction (protonation) with the formation of the polymer salt as well as the coordination of Pd 21 ions by the nitrogen atoms of the polymer take place. In the PdCl2 solutions of low HCl concentration containing [PdCl2(H2O) 2] as the major species protonation proceeds to a small extent. The main process in this case is most probably hydrolysis of the latter with the precipitation of hydrated palladium hydroxide or oxide on the polymer surface. In the case of PANI the oxidation‐reduction between this precipitate and PANI takes place. It results in the oxidation of the polymer chain. q 1999 Elsevier Science B.V. All rights reserved.

Spectroscopic studies of polyaniline protonation with poly(alkylene phosphates)

Abstract Polyaniline doped with poly(alkylene phosphates) has been studied by Fourier transform infra-red, X-ray photoelectron and ultraviolet/visible spectroscopies. The protonation of the polymer was indicated by the appearance of infra-red modes characteristic of polyaniline salts and by the bands typical of polyphosphates at ca. 1000 cm−1. X-ray photoelectron spectra showed a decrease in the concentration of imine groups as well as the co-existence of ionized and unionized phosphates independent of the doping level. The influence of the protonation method on the obtained product was observed.

Interactions between polyanilines and palladium ions: similarities and differences

Polyaniline (PANI), poly(o-toluidine) (POT) and poly(o-chloroaniline) (POC) were treated with PdCl 2 , palladium (II) acetate and palladium (II) acetylacetonate in organic solvents. It was found that polymer-palladium interactions involved predominantly a redox -type reaction which resulted in the partial oxidation of the polymer chain with simultaneous reduction of some Pd 2+ to Pd°. In the systems studied PANI exhibited the strongest redox properties towards Pd 2+ ions, POT weaker and POC the weakest ones.

Polypyrrole-palladium systems prepared in PdCl2 aqueous solutions

Abstract In the work, reactions of a partially deprotonated polypyrrole doped with hydroxide ions (PPyOH) in various PdCl2 aqueous solutions which differed in acidity were studied. Using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy it was established that in the PdCl2 solutions of lower acidity PPyOH was oxidatively doped and Pd0 and Pd2+ were incorporated into the polymer matrix. Pd2+ formed palladium(II) hydroxy-and/or aquochlorocomplex dopant anions and/or was coordinated by nitrogen atoms of the polymer (Pd–N bond). Additionally, deprotonation of PPyOH occurred in the PdCl2 solutions of lower acidity. It was proposed that deprotonation of PPyOH was caused by nucleophilic attack of [PdCl3(H2O)]− on the positively charged, doped polymer chain. By comparison of the PPyOH and chloride-doped polypyrrole (PPyCl)–palladium systems prepared in similar PdCl2 solutions of lower acidity it was shown that the type of the counterion in the starting polymer has a decisive effect on the deprotonation process. PPyOH was less reactive towards palladium species in the PdCl2 solutions of higher acidity where [PdCl4]2− was the dominant complex. PPy–palladium systems containing exclusively Pd2+ were obtained in this case. It was proposed that incorporation of palladium species in these conditions proceeded via an acid–base reaction or coordination of palladium ions by the polymer chain (Pd–N bond formation). Results of the studies may serve as the basis for the preparation of a variety of polypyrrole-supported palladium catalysts.

Preceramic polysiloxane networks obtained by hydrosilylation of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane.

Precreamic polysiloxane networks were prepared by hydrosilylation of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (D(4)(Vi)) with a series of linear hydrogensiloxanes as well as with a cyclic hydrogensiloxane, namely 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) at various hydrogensiloxane/D(4)(Vi) molar ratios in the starting reaction mixture. FTIR spectroscopic measurements conducted during the processes as well as for the reaction products allowed to reveal that the rate of D(4)(Vi) hydrosilylation as well as its efficiency are influenced by the type of hydrogensiloxane used and by the reactants molar ratio. Ceramic yields determined at 1000°C by thermogravimetric analyses were higher for D(4)(Vi)-D(4)(H) than for D(4)(Vi) - linear hydrogensiloxane networks (86-89% vs 65-76%, respectively). Preceramic polysiloxanes prepared as well as the products of their pyrolysis obtained after thermal investigations were monolithic, pore-less materials.

Conductive blends of polyaniline with plasticized poly(methyl methacrylate)

Polyaniline (PANI) protonated with camphorsulfonic acid (CSA) and three different poly(alkylene phosphates) (PAPs) (where alkylene = pentylene, hexylene, or nonylene) was used in the fabrication of conductive polyaniline-poly(methyl methacrylate) (PMMA) blends. The lowest percolation threshold (f p = 0.041 wt %) was obtained for the PANI(CSA) 0.5 -PMMA blend plasticized with 35 wt % of dibutyl phtalate (DBPh). This blend is also very resistant against the deprotonation of its conductive phase in basic solutions of pH = 9. In the case of blends prepared with the use of PAPs as PANI dopants, the percolation threshold strongly depends on the length of the hydrophobic spacer (alkylene group) in the dopant. The percolation threshold decreases in the order PPP > PHP > PNP, whereas the resistance against deprotonation in basic solutions decreases in the following inverse order: PNP > PHP > PPP. This last observation can be rationalized by increasing contribution of hydrophobic segments in the polymeric dopant, when going from PPP to PNP, which renders polyaniline more resistance toward the penetration by aqueous basic solutions.