Tarmo Tamm | University of Tartu (original) (raw)

Papers by Tarmo Tamm

Chemistry of Heterocyclic Compounds, 2018

Double bond isomerization by in situ generated ruthenium hydride catalyst in 6-to 9-membered hydr... more Double bond isomerization by in situ generated ruthenium hydride catalyst in 6-to 9-membered hydrazine heterocycles including an endocyclic N-N bond was investigated. Based on the results of the experiments, a conclusion was made that the generation of resonancestabilized enehydrazides is generally favored, but in some cases, the reaction pathway is presumably also highly dependent of steric interactions. With the current method, two novel enehydrazide heterocycles and one enehydrazine heterocycle were produced and characterized.

The Journal of Physical Chemistry B, 2012

The ionic motion in connection with the redox transformation of poly(3,4ethylenedioxythiophene) (... more The ionic motion in connection with the redox transformation of poly(3,4ethylenedioxythiophene) (PEDOT) conjugated polymer have been studied by both experimental: electrochemical (electrochemical quartz crystal nanobalance-EQCN), spectroscopic (Infrared spectroscopy-IR-ATR); and theoretical methods. The observations have been completed by

Synthetic Metals, 2020

In ionic systems, like those of conducting polymers, the direction of actuation (as well as-natur... more In ionic systems, like those of conducting polymers, the direction of actuation (as well as-naturally-the amplitude) depends on the dominance of one type of ions (cations over anions or vice versa) as the mobile species, maintaining charge neutrality. Here we demonstrate that the same polypyrrole (PPy) films can have rather different response in terms of linear actuation amplitude as well as direction under different voltage ranges. A system designed to mitigate such uncertainties-PPy blended with polymerized ionic liquidis shown as a comparison. Three reversible and charge-balanced potential ranges in cyclic voltammetry and square wave voltage steps experiments were chosen to demonstrate the importance of selecting the right voltage range, especially if no embedded charges acting as "filters" are being used.

Materials Today Communications, 2020

Current research on conducting polymer composite actuators has been mainly focused on achieving i... more Current research on conducting polymer composite actuators has been mainly focused on achieving increased linear actuation with improved electrical, physical and chemical properties. Polyethylene oxide (PEO) has been shown to enhance both mechanical and electrical properties of conducting polymers at certain concentrations. However, as some of these effects peak off, the optimal concentration is difficult to determine. In this study, polypyrrole (PPy)-PEO composite films, doped with dodecylbenzene sulfonate, were electropolymerized from solutions with different concentrations of PEO. The obtained films were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman, FTIR and energy dispersive X-ray spectroscopy (EDX). Electrochemical impedance spectroscopy (EIS) and modified scanning ionic conductance microscopy (mSICM) allowed the determination of electronic and ionic conductivities of the samples. Their electro-chemo-mechanical deformations (ECMD) were investigated under cyclic voltammetry. In aqueous electrolyte, the samples showed expansion/contraction during reduction/oxidation, respectively (cation-driven), while opposite behaviourexpansion/contraction during oxidation/reduction (anion-driven) behaviour was observed in propylene carbonate solutions. These films obtained from solutions with a PEO content of 5% showed the highest deformations (strain and stress). They also presented the highest ionic and electronic conductivities and redox charge density. The ECMD deformation per unit of redox charge was much higher in PC solutions than in aqueous solutions: more PC molecules are exchanged for osmotic balance per unit of redox charge.

Journal of Applied Polymer Science, 2018

Ionic conductivity of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) was improved by ... more Ionic conductivity of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) was improved by loading of 10 wt % of polyethylene oxide (PEO). The linear actuation properties of PPy-PEO/DBS films were investigated and compared in polar (aqueous) and aprotic (propylene carbonate) solvents keeping the concentration of lithium bis(trifluoromethane)sulfonimide (LiTFSI) electrolyte the same. The results were compared to those of pristine PPy/DBS films. The actuation direction changed from pure cation-driven in the aqueous electrolyte (LiTFSI(aq)) to anion-driven in propylene carbonate electrolyte (LiTFSI(PC)). At the same time, the electrochemo-mechanical deformation revealed that the strain of PPy-PEO/DBS increased from 5% in LiTFSI(aq) to 20% in LiTFSI(PC). The effect of solvent on the ionic conductivity was investigated using electrochemical impedance spectroscopy, showing a 27% increase in charge transfer kinetics and an increase in the electronic conductivity, resulting in significant increase in the strain rate, when propylene carbonate electrolyte was used.

Synthetic Metals, 2017

Polypyrrole (PPy) was chemically deposited on glycose-crosslinked gelatin fiber scaffold (FS) by ... more Polypyrrole (PPy) was chemically deposited on glycose-crosslinked gelatin fiber scaffold (FS) by simple dip coating technique, resulting in conductive fiber scaffolds (CFS). The CFS samples were comparatively studied in aqueous and propylene carbonate solutions of equal concentrations of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) electrolyte. Our aim in this work was to characterize the mechanical and electrochemical properties of the CFS samples. The new CFS material was characterized by scanning electron microscopy (SEM) and FTIR measurements confirming chemical oxidized PPy deposits on FS. The electrochemical measurements applying cyclic voltammetric, chronoamperometric and chronopotentiometric measurements showed that while diffusion coefficients for both solvents were in similar range, the exchanged charge was nearly doubled in aqueous solutions. The specific capacitance of the CFS had the highest value in aqueous electrolyte reaching 175 F g −1 , which suggests that in addition to smart tissue engineering, this novel CFS material could also find application in energy storage.

Smart Materials and Structures, 2019

Nanoscale, 2018

Toxicity and cancer-killing potency of Fe-doped ZnO nanoparticles can be reliably modelled using ... more Toxicity and cancer-killing potency of Fe-doped ZnO nanoparticles can be reliably modelled using atomistic nanodescriptors.

Synthetic Metals, 2017

In the present paper, we report the electro-chemo-mechanical deformation (ECMD) measurements of p... more In the present paper, we report the electro-chemo-mechanical deformation (ECMD) measurements of pristine polypyrrole (PPy) and polypyrrole/poly(ethylene oxide) composite films doped with dodecylbenzenesulfonate (DBS) under isotonic (constant force) conditions. The PPy/DBS and PPy-PEO/DBS films, the latter made from a polymerization solution containing 5 wt% PEO, were actuated potentiodynamically in an aqueous solution containing lithium bis-trifluoromethane-sulfonimide (LiTFSI). The obtained composite films were characterized with scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results confirmed the successful incorporation of PEO within the PPy film. The composite films showed a remarkable improvement in maximum strain achieved (of 7.7%), nearly double that of the pristine PPy/DBS film, had a higher conductivity, higher ion diffusion coefficient and faster strain rate. The ECMD measurements for both the pristine as well as the PEO-composite films showed cation driven actuation involving the migration of Li + cations in the aqueous electrolyte.

Sensors and Actuators B: Chemical, 2017

Co-doping polypyrrole (PPy) with dodecylbenzenesulfonate and multicharged phosphotungstate anions... more Co-doping polypyrrole (PPy) with dodecylbenzenesulfonate and multicharged phosphotungstate anions (PT) from the phosphotungstic acid (PTA) led to free-standing PPy/DBS-PT films, which were studied for their linear actuation properties. FTIR and Raman spectra revealed that PT was successfully embedded in PPy/DBS during electropolymerisation. Isometric stress and isotonic strain measurements in aqueous electrolyte under various electrochemical experiments showed an increase in the obtainable strain and stress, which was attributed to the electrocatalytic role PTA plays during the electropolymerisation. This results in lower synthesis potential and the formation of more compact films in comparison to PPy/DBS films under equal conditions. With the improved structure as well as the higher-charged immobilized PT dopant, 17 times higher conductivities, 1.7 times higher redox charge, and 1.8 times higher specific capacitance were obtained (at equal frequency). Energy dispersive X-ray (EDX) spectra indicated that contrary to some other published works, the majority of PT stayed stably in the film during consecutive redox cycles.

Advanced healthcare materials, Jan 23, 2017

Cancer cells have unique but widely varying characteristics that have proven them difficult to be... more Cancer cells have unique but widely varying characteristics that have proven them difficult to be treated by classical therapeutics and calls for novel and selective treatment options. Nanomaterials (NMs) have been shown to display biological effects as a function of their chemical composition, and the extent and exact nature of these effects can vary between different biological environments. Here, ZnO NMs are doped with increasing levels of Fe, which allows to finely tune their dissolution rate resulting in significant differences in their biological behavior on cancer or normal cells. Based on in silico analysis, 2% Fe-doped ZnO NMs are found to be optimal to cause selective cancer cell death, which is confirmed in both cultured cells and syngeneic tumor models, where they also reduce metastasis formation. These results show that upon tuning NM chemical composition, NMs can be designed as a targeted selective anticancer therapy.

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

International Journal of Nanotechnology, 2014

The electrochemical deposition of a conducting polymer on a non-conductive polymer requires a con... more The electrochemical deposition of a conducting polymer on a non-conductive polymer requires a conductive layer, which can be achieved by sputtering or vaporisation of precious metals such as gold or platinum. In this investigation we coated poly(styrenesulphonate) doped poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes (PEDOT-PSS/MWCNT), in a ratio of 2.4 : 1 on a poly(ethylene terephthalate) (PET) layer and investigated the electrochemical stability of the nanotechnology composite. The properties of the PEDOT-PSS/MWCNT in respect to flexibility and strain were studied, and it was shown that strains

Solid State Ionics, 2014

ABSTRACT Classical Molecular Dynamics (MD) simulation studies of the single-ion conductor lithium... more ABSTRACT Classical Molecular Dynamics (MD) simulation studies of the single-ion conductor lithium poly(4-styrenesul-fonyl(trifluorosulfonyl)imide) (PSTFSI) are for the first time presented here. The polymer electrolyte system comprises anions which are covalently bonded to a polymer backbone, thus rendering very high positive trans-port numbers. The studies here include a quantum chemistry based force field generation for this system and MD simulations of PSTFSI and a blend between PSTFSI and poly(ethylene oxide) (PEO). The simulations show that PEO acts as a very good solvent for the Li-ions, and that the transport properties are similar to Li-salt/PEO electro-lytes at room temperature conditions, while pure PSTFSI has very little Li mobility at all. Realistic Li diffusion co-efficients of ~1 × 10 −13 m 2 s −1 were generated for the PSTFSI/PEO blend.

Synthetic Metals, 2005

The complexes of pyrrole oligomer dications with various inorganic anions were studied using a va... more The complexes of pyrrole oligomer dications with various inorganic anions were studied using a variety of computational methods ranging from semi-empirical to density functional theory (DFT) and MP2. The geometry of the complexes and the differences in complexation energies are discussed. The differences in the stability of the complexes compare favorably to experimentally known trends of anion mobilities in polypyrrole films.

Reactive and Functional Polymers, 2013

Conductive polymers have the ability to capture radicals and have become in focus for antioxidant... more Conductive polymers have the ability to capture radicals and have become in focus for antioxidant applications of food packaging or biomedical applications. Unfortunately, the conducting polymers such as polypyrrole are difficult to suspense in solution after chemical or electrochemical polymerization. Chitosan, as a natural polymer from chitin, can be dissolved in diluted acetic acid solutions. In the present study, composites suspensible in diluted acetic acid solutions have been produced by the chemical polymerization of pyrrole in chitosan solution using ammonium persulfate (APS) as the oxidant. FTIR and UV-Vis measurements did identify an attachment of polypyrrole to chitosan. In order to optimize the activity and stability of the composites, the ratios of APS : polypyrrole : chitosan were analyzed. The chitosan-polypyrrole composites were formed as membranes (coatings); impedance measurements indicated their conductivity to be in the range of 10-3-10-7 S cm-1. The antioxidant (radical scavenger activity) properties were determined by the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assay. The radical scavenger activity of the composites was found renewable by means of electrochemical cycling.

Molecular Informatics, 2013

The article deals with a challenging attempt to model and predict “difficult” properties as long‐... more The article deals with a challenging attempt to model and predict “difficult” properties as long‐term subchronic oral and inhalation toxicities (90 days) using nonlinear QSAR approach. This investigation is one of the first to tackle such multicomplex properties where we have employed nonlinear models based on artificial neural network for the prediction of NOAEL (no observable adverse effect level). Despite the complex nature of the NOAEL property based on in vivo rat experiments, the successful models can be used as alternative tools to non‐animal tests for the initial assessment of these chronic toxicities. The model for oral subchronic toxicity is able to describe 88 %, and the inhalation model 87 % of the statistical variance. For the sake of future predictions, we have also defined in a quantitative way the applicability domain of all neural network models.

Chemistry of Heterocyclic Compounds, 2018

Double bond isomerization by in situ generated ruthenium hydride catalyst in 6-to 9-membered hydr... more Double bond isomerization by in situ generated ruthenium hydride catalyst in 6-to 9-membered hydrazine heterocycles including an endocyclic N-N bond was investigated. Based on the results of the experiments, a conclusion was made that the generation of resonancestabilized enehydrazides is generally favored, but in some cases, the reaction pathway is presumably also highly dependent of steric interactions. With the current method, two novel enehydrazide heterocycles and one enehydrazine heterocycle were produced and characterized.

The Journal of Physical Chemistry B, 2012

The ionic motion in connection with the redox transformation of poly(3,4ethylenedioxythiophene) (... more The ionic motion in connection with the redox transformation of poly(3,4ethylenedioxythiophene) (PEDOT) conjugated polymer have been studied by both experimental: electrochemical (electrochemical quartz crystal nanobalance-EQCN), spectroscopic (Infrared spectroscopy-IR-ATR); and theoretical methods. The observations have been completed by

Synthetic Metals, 2020

In ionic systems, like those of conducting polymers, the direction of actuation (as well as-natur... more In ionic systems, like those of conducting polymers, the direction of actuation (as well as-naturally-the amplitude) depends on the dominance of one type of ions (cations over anions or vice versa) as the mobile species, maintaining charge neutrality. Here we demonstrate that the same polypyrrole (PPy) films can have rather different response in terms of linear actuation amplitude as well as direction under different voltage ranges. A system designed to mitigate such uncertainties-PPy blended with polymerized ionic liquidis shown as a comparison. Three reversible and charge-balanced potential ranges in cyclic voltammetry and square wave voltage steps experiments were chosen to demonstrate the importance of selecting the right voltage range, especially if no embedded charges acting as "filters" are being used.

Materials Today Communications, 2020

Current research on conducting polymer composite actuators has been mainly focused on achieving i... more Current research on conducting polymer composite actuators has been mainly focused on achieving increased linear actuation with improved electrical, physical and chemical properties. Polyethylene oxide (PEO) has been shown to enhance both mechanical and electrical properties of conducting polymers at certain concentrations. However, as some of these effects peak off, the optimal concentration is difficult to determine. In this study, polypyrrole (PPy)-PEO composite films, doped with dodecylbenzene sulfonate, were electropolymerized from solutions with different concentrations of PEO. The obtained films were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman, FTIR and energy dispersive X-ray spectroscopy (EDX). Electrochemical impedance spectroscopy (EIS) and modified scanning ionic conductance microscopy (mSICM) allowed the determination of electronic and ionic conductivities of the samples. Their electro-chemo-mechanical deformations (ECMD) were investigated under cyclic voltammetry. In aqueous electrolyte, the samples showed expansion/contraction during reduction/oxidation, respectively (cation-driven), while opposite behaviourexpansion/contraction during oxidation/reduction (anion-driven) behaviour was observed in propylene carbonate solutions. These films obtained from solutions with a PEO content of 5% showed the highest deformations (strain and stress). They also presented the highest ionic and electronic conductivities and redox charge density. The ECMD deformation per unit of redox charge was much higher in PC solutions than in aqueous solutions: more PC molecules are exchanged for osmotic balance per unit of redox charge.

Journal of Applied Polymer Science, 2018

Ionic conductivity of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) was improved by ... more Ionic conductivity of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) was improved by loading of 10 wt % of polyethylene oxide (PEO). The linear actuation properties of PPy-PEO/DBS films were investigated and compared in polar (aqueous) and aprotic (propylene carbonate) solvents keeping the concentration of lithium bis(trifluoromethane)sulfonimide (LiTFSI) electrolyte the same. The results were compared to those of pristine PPy/DBS films. The actuation direction changed from pure cation-driven in the aqueous electrolyte (LiTFSI(aq)) to anion-driven in propylene carbonate electrolyte (LiTFSI(PC)). At the same time, the electrochemo-mechanical deformation revealed that the strain of PPy-PEO/DBS increased from 5% in LiTFSI(aq) to 20% in LiTFSI(PC). The effect of solvent on the ionic conductivity was investigated using electrochemical impedance spectroscopy, showing a 27% increase in charge transfer kinetics and an increase in the electronic conductivity, resulting in significant increase in the strain rate, when propylene carbonate electrolyte was used.

Synthetic Metals, 2017

Polypyrrole (PPy) was chemically deposited on glycose-crosslinked gelatin fiber scaffold (FS) by ... more Polypyrrole (PPy) was chemically deposited on glycose-crosslinked gelatin fiber scaffold (FS) by simple dip coating technique, resulting in conductive fiber scaffolds (CFS). The CFS samples were comparatively studied in aqueous and propylene carbonate solutions of equal concentrations of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) electrolyte. Our aim in this work was to characterize the mechanical and electrochemical properties of the CFS samples. The new CFS material was characterized by scanning electron microscopy (SEM) and FTIR measurements confirming chemical oxidized PPy deposits on FS. The electrochemical measurements applying cyclic voltammetric, chronoamperometric and chronopotentiometric measurements showed that while diffusion coefficients for both solvents were in similar range, the exchanged charge was nearly doubled in aqueous solutions. The specific capacitance of the CFS had the highest value in aqueous electrolyte reaching 175 F g −1 , which suggests that in addition to smart tissue engineering, this novel CFS material could also find application in energy storage.

Smart Materials and Structures, 2019

Nanoscale, 2018

Toxicity and cancer-killing potency of Fe-doped ZnO nanoparticles can be reliably modelled using ... more Toxicity and cancer-killing potency of Fe-doped ZnO nanoparticles can be reliably modelled using atomistic nanodescriptors.

Synthetic Metals, 2017

In the present paper, we report the electro-chemo-mechanical deformation (ECMD) measurements of p... more In the present paper, we report the electro-chemo-mechanical deformation (ECMD) measurements of pristine polypyrrole (PPy) and polypyrrole/poly(ethylene oxide) composite films doped with dodecylbenzenesulfonate (DBS) under isotonic (constant force) conditions. The PPy/DBS and PPy-PEO/DBS films, the latter made from a polymerization solution containing 5 wt% PEO, were actuated potentiodynamically in an aqueous solution containing lithium bis-trifluoromethane-sulfonimide (LiTFSI). The obtained composite films were characterized with scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results confirmed the successful incorporation of PEO within the PPy film. The composite films showed a remarkable improvement in maximum strain achieved (of 7.7%), nearly double that of the pristine PPy/DBS film, had a higher conductivity, higher ion diffusion coefficient and faster strain rate. The ECMD measurements for both the pristine as well as the PEO-composite films showed cation driven actuation involving the migration of Li + cations in the aqueous electrolyte.

Sensors and Actuators B: Chemical, 2017

Co-doping polypyrrole (PPy) with dodecylbenzenesulfonate and multicharged phosphotungstate anions... more Co-doping polypyrrole (PPy) with dodecylbenzenesulfonate and multicharged phosphotungstate anions (PT) from the phosphotungstic acid (PTA) led to free-standing PPy/DBS-PT films, which were studied for their linear actuation properties. FTIR and Raman spectra revealed that PT was successfully embedded in PPy/DBS during electropolymerisation. Isometric stress and isotonic strain measurements in aqueous electrolyte under various electrochemical experiments showed an increase in the obtainable strain and stress, which was attributed to the electrocatalytic role PTA plays during the electropolymerisation. This results in lower synthesis potential and the formation of more compact films in comparison to PPy/DBS films under equal conditions. With the improved structure as well as the higher-charged immobilized PT dopant, 17 times higher conductivities, 1.7 times higher redox charge, and 1.8 times higher specific capacitance were obtained (at equal frequency). Energy dispersive X-ray (EDX) spectra indicated that contrary to some other published works, the majority of PT stayed stably in the film during consecutive redox cycles.

Advanced healthcare materials, Jan 23, 2017

Cancer cells have unique but widely varying characteristics that have proven them difficult to be... more Cancer cells have unique but widely varying characteristics that have proven them difficult to be treated by classical therapeutics and calls for novel and selective treatment options. Nanomaterials (NMs) have been shown to display biological effects as a function of their chemical composition, and the extent and exact nature of these effects can vary between different biological environments. Here, ZnO NMs are doped with increasing levels of Fe, which allows to finely tune their dissolution rate resulting in significant differences in their biological behavior on cancer or normal cells. Based on in silico analysis, 2% Fe-doped ZnO NMs are found to be optimal to cause selective cancer cell death, which is confirmed in both cultured cells and syngeneic tumor models, where they also reduce metastasis formation. These results show that upon tuning NM chemical composition, NMs can be designed as a targeted selective anticancer therapy.

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

International Journal of Nanotechnology, 2014

The electrochemical deposition of a conducting polymer on a non-conductive polymer requires a con... more The electrochemical deposition of a conducting polymer on a non-conductive polymer requires a conductive layer, which can be achieved by sputtering or vaporisation of precious metals such as gold or platinum. In this investigation we coated poly(styrenesulphonate) doped poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes (PEDOT-PSS/MWCNT), in a ratio of 2.4 : 1 on a poly(ethylene terephthalate) (PET) layer and investigated the electrochemical stability of the nanotechnology composite. The properties of the PEDOT-PSS/MWCNT in respect to flexibility and strain were studied, and it was shown that strains

Solid State Ionics, 2014

ABSTRACT Classical Molecular Dynamics (MD) simulation studies of the single-ion conductor lithium... more ABSTRACT Classical Molecular Dynamics (MD) simulation studies of the single-ion conductor lithium poly(4-styrenesul-fonyl(trifluorosulfonyl)imide) (PSTFSI) are for the first time presented here. The polymer electrolyte system comprises anions which are covalently bonded to a polymer backbone, thus rendering very high positive trans-port numbers. The studies here include a quantum chemistry based force field generation for this system and MD simulations of PSTFSI and a blend between PSTFSI and poly(ethylene oxide) (PEO). The simulations show that PEO acts as a very good solvent for the Li-ions, and that the transport properties are similar to Li-salt/PEO electro-lytes at room temperature conditions, while pure PSTFSI has very little Li mobility at all. Realistic Li diffusion co-efficients of ~1 × 10 −13 m 2 s −1 were generated for the PSTFSI/PEO blend.

Synthetic Metals, 2005

The complexes of pyrrole oligomer dications with various inorganic anions were studied using a va... more The complexes of pyrrole oligomer dications with various inorganic anions were studied using a variety of computational methods ranging from semi-empirical to density functional theory (DFT) and MP2. The geometry of the complexes and the differences in complexation energies are discussed. The differences in the stability of the complexes compare favorably to experimentally known trends of anion mobilities in polypyrrole films.

Reactive and Functional Polymers, 2013

Conductive polymers have the ability to capture radicals and have become in focus for antioxidant... more Conductive polymers have the ability to capture radicals and have become in focus for antioxidant applications of food packaging or biomedical applications. Unfortunately, the conducting polymers such as polypyrrole are difficult to suspense in solution after chemical or electrochemical polymerization. Chitosan, as a natural polymer from chitin, can be dissolved in diluted acetic acid solutions. In the present study, composites suspensible in diluted acetic acid solutions have been produced by the chemical polymerization of pyrrole in chitosan solution using ammonium persulfate (APS) as the oxidant. FTIR and UV-Vis measurements did identify an attachment of polypyrrole to chitosan. In order to optimize the activity and stability of the composites, the ratios of APS : polypyrrole : chitosan were analyzed. The chitosan-polypyrrole composites were formed as membranes (coatings); impedance measurements indicated their conductivity to be in the range of 10-3-10-7 S cm-1. The antioxidant (radical scavenger activity) properties were determined by the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assay. The radical scavenger activity of the composites was found renewable by means of electrochemical cycling.

Molecular Informatics, 2013

The article deals with a challenging attempt to model and predict “difficult” properties as long‐... more The article deals with a challenging attempt to model and predict “difficult” properties as long‐term subchronic oral and inhalation toxicities (90 days) using nonlinear QSAR approach. This investigation is one of the first to tackle such multicomplex properties where we have employed nonlinear models based on artificial neural network for the prediction of NOAEL (no observable adverse effect level). Despite the complex nature of the NOAEL property based on in vivo rat experiments, the successful models can be used as alternative tools to non‐animal tests for the initial assessment of these chronic toxicities. The model for oral subchronic toxicity is able to describe 88 %, and the inhalation model 87 % of the statistical variance. For the sake of future predictions, we have also defined in a quantitative way the applicability domain of all neural network models.