Despina Triantou - Academia.edu (original) (raw)

Papers by Despina Triantou

Research paper thumbnail of Effect of the acceptor moiety on the electrochemical and electrochromic properties of Donor-Acceptor-Donor polymer films

International Journal of Electrochemical Science, Apr 1, 2015

The aim of this work is to synthesize EC polymers having green or blue colour in the neutral stat... more The aim of this work is to synthesize EC polymers having green or blue colour in the neutral state and transparent oxidized state by using the D-AD approach. Two different monomers, diphenylthienopyrazine (M1) and diphenylquinoxaline (M2) are synthesized. The monomers are successfully electropolymerized to P1 and P2, respectively, by cyclic voltammetry on ITO substrates. The effect of the acceptor moiety on the electrochemical and electrochromic properties of the polymer films is investigated. Both polymers exhibit the characteristic redox couple due to their oxidation/reduction at 0.95 V/0.62 V for P1 and at 1.05 V/0.35 V for P2; their doping/dedoping reaction is reversible. The two polymers have different optical properties; namely, the phenyl ring in the acceptor unit (P2) caused hypsochromic shift. The acceptor moiety affects mainly the LUMO level; specifically, the LUMO level shifted to less negative values by replacing thiophene with phenyl. The electrochromic properties of the polymer films are strongly affected by the acceptor moiety. Polymer P1 changes its colour from green (neutral state), to grey (intermediate oxidised state), to transparent grey/sky blue (oxidized state) and to lemon green (reduced state). Correspondingly, P2 starts from royal blue (neutral state), going to blue purple, grey-blue and light grey (intermediate oxidised states) and then to green (oxidized state); additionally, it became also oil green and light blue (reduced states). Both polymers are multicoloured and were good candidates for application in electrochromic devices.

Research paper thumbnail of Synthesis and characterization of electrically conducting copolymers based on biphenyl and thiophene

Journal of Applied Polymer Science, Jun 3, 2010

ABSTRACT

Research paper thumbnail of Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

Journal of Applied Polymer Science, Oct 5, 2008

ABSTRACT

Research paper thumbnail of Thiophene-Based Copolymers Synthesized by Electropolymerization for Application as Hole Transport Layer in Organic Photovoltaics Cells

Springer eBooks, Oct 16, 2013

Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The... more Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The potential range used has a strong influence on the film structure and properties. The extent of oxidation of the copolymers was determined from the ratio of the oxidation to reduction charge, Q ox /Q red. The use of wide potential range leads to reduced films, whereas the narrow range leads to partially oxidized films. The copolymers exhibit a characteristic band in UV-vis spectra at $ 410 nm, which shifts to higher wavelengths for the more doped material. The electrical conductivity of the copolymers was correlated to their morphology and their structure. The copolymer with higher conductivity is partially reduced, has compact morphology and higher ratio of quinoid to benzenoid rings. The energy gap of the copolymers is reversely proportional to their electrical conductivity. The optical and electrical properties of the copolymers make them very well suited for use as hole transport layers (HTL) in organic opto-electronic devices. We prepared polymer : fullerene solar cells with copolymer HTLs. The solar cell performance was tested with very encouraging initial results. V

Research paper thumbnail of Electrochemical synthesis and characterization of conducting copolymers of biphenyl with pyrrole

Journal of Applied Polymer Science, Jan 18, 2012

The electrochemical oxidation of anodic metal (zinc or cadmium) in acetonitrile solution of the p... more The electrochemical oxidation of anodic metal (zinc or cadmium) in acetonitrile solution of the potentially chelating Schiff base N,N-(dithiodiethylenebis(aminylydenemethylydene)bis(1,2-phenylene)ditosylamide (H 2 L) afforded stable complexes of empirical formula [ML]. The crystal and molecular structures of [ZnL] • CH 3 CN (1) and [CdL] (2) have been determined by X-ray diffraction. In both complexes the metal atom is in a distorted

Research paper thumbnail of Synthesis of Thiophene-Based Copolymers for Application in Dual Layer ECDs

Dual layer electrochromic devices (ECDs) were constructed using copolymers synthesized from elect... more Dual layer electrochromic devices (ECDs) were constructed using copolymers synthesized from electron donor-acceptordonor (D-A-D) monomers with thiophene-based donor moieties. Comonomers having different D-A-D structures were synthesized and successfully electropolymerized as uniform films onto ITO. The properties of the films depended on the acceptor moiety. Compared to the corresponding single layer ECDs, the dual layer devices exhibited genuine multicoloured EC behavior and improved operational characteristics. Further development of the dual layer ECDs is expected to lead towards optimized performance.

Research paper thumbnail of Influence of electrochemical copolymerization conditions of 3-methylthiophene and biphenyl on the morphology and nanomechanical properties of the films

Journal of Applied Polymer Science, 2015

N-Acetyltra change in classificatio the present covered exo identified m Overall, we acetylators ... more N-Acetyltra change in classificatio the present covered exo identified m Overall, we acetylators were found detected in gender diffe

Research paper thumbnail of Structural analysis of biodegradable low-molecular mass copolyesters based on glycolic acid, adipic acid and 1,4 butanediol and correlation with their hydrolytic degradation

Polymer Degradation and Stability, 2012

Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, thei... more Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, their in vitro hydrolytic degradation was studied and correlated with their structure. The hydrolytic degradation of the copolyesters was directly related with the degree of crystallinity and the diameter of the crystallites. It was found that glycolate units disturb the ordering of the butylene adipate units, which results in a decrease of the crystallinity. By comparing the hydrolysis parameters of synthesized copolyesters with those of similar aliphatic copolyesters a hydrolysis mechanism was proposed. According to this mechanism, the degradation takes place not only by the loss of end units, but also through the removal of larger segments. MALDI-TOF MS data showed that the possibility of a copolyester macromolecule forming cyclic structures correlates with the arrangement of ester groups in the macromolecules and the structure of the linear segments.

Research paper thumbnail of Synthesis of Copolymers Based on Benzene and Biphenyl and their Characterization by XRD and DSC

Journal of Research Updates in Polymer Science, 2012

In this work the crystalinity and the thermal transitions of soluble and insoluble in chlorobenze... more In this work the crystalinity and the thermal transitions of soluble and insoluble in chlorobenzene polyphenylene copolymers (synthesized by oxidative cationic polymerization) were studied. All copolymers had a degree of crystallinity between 44.6 and 66.7 %. With Differential Scanning Calorimentry (DSC) measurements it was found that the copolymers exhibited endothermic peaks in the region 268 up to 286 oC. These peaks in the case of soluble polyphenylenes were attributed to the melting of their crystallites, whereas in the case of insoluble polyphenylenes were attributed to liquid crystal transitions.

Research paper thumbnail of Ηλεκτρικά αγώγιμα συμπολυμερή βάσεως πολυφαινυλενίων

Research paper thumbnail of Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid, sebacic acid and ethylene glycol

Journal of Materials Science: Materials in Medicine, 2011

Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthes... more Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0-100% and S: 100-0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I 2918 , I 2848 and I 1087 for the corresponding wavenumbers, it is concluded that the I 2918 and the I 2848 are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I 1087 is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and fourparameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.

Research paper thumbnail of Correlation of hydrolytic degradation with structure for copolyesters produced from glycolic and adipic acids

Journal of Materials Science: Materials in Medicine, 2009

Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) wer... more Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100-50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm-1 can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm-1 due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm-1 due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.

Research paper thumbnail of Electrochemical grafting of 4-phenoxybenzoic acid units onto oxidized carbon fibers as a first step for high temperature composites

Journal of Applied Polymer Science, 2013

The electropolymerization of 4-phenoxybenzoic acid (4-PBA) onto carbon fibers (CFs) was studied a... more The electropolymerization of 4-phenoxybenzoic acid (4-PBA) onto carbon fibers (CFs) was studied as a way to synthesize coated CFs with grafted poly(para-phenyl ether ketone) (p-PEK) and enhance their wettability by matrices such as PEK or PEEK. Since the pristine CFs were not electrochemically active enough, a proper electrochemical oxidation treatment using sulfuric acid was applied, capable of creating oxygen-containing groups onto their surface. The groups formed in the oxidized CFs were electron acceptors and their amount was quasi-quantitatively evaluated based on their ability to absorb dye from aqueous solutions. The graft electropolymerization of 4-PBA onto the CFs electrode was achieved at anodic potentials using cyclic voltammetry (CV). The grafted coating had a thickness of up to 0.35 lm. The materials were characterized using FTIR, NMR, SEM, and TGA. A possible reaction mechanism is proposed, for the grafting of 4-PBA units onto the carboxyl groups of the treated CFs. The coated CFs were more thermally stable compared to the treated CFs without grafting.

Research paper thumbnail of Influence of backbone rigidity on the curing and the dielectric relaxations of unsaturated polyesters

Journal of Applied Polymer Science, 2010

ABSTRACT

Research paper thumbnail of Electrical conductivity and mechanical strength of composites consisting of phenolic resin, carbon fibers, and metal particles

Journal of Applied Polymer Science, 2011

Composites of phenolic resin of novolac type as matrix, with metal particles of Zn as conducting ... more Composites of phenolic resin of novolac type as matrix, with metal particles of Zn as conducting filler, without or with 15% v/v carbon fibers were manufactured by hot pressing. The porosity ratio, the hardness, the flexural and shear strength, and the electrical conductivity of the composites were determined. The percolation threshold was determined based on two models of electrical conductivity versus the content of metal particles of Zn, namely, an analogous to polymer gelation model and the other based on the power law. The composites of carbon fibers combined with Zn particles have higher electrical conductivity than the corresponding without carbon fibers and high strength, lower than that of the composite reinforced with carbon fibers without Zn particles, but still acceptable.

Research paper thumbnail of Thiophene-based copolymers synthesized by electropolymerization for application as hole transport layer in organic solar cells

Journal of Applied Polymer Science, 2012

Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The... more Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The potential range used has a strong influence on the film structure and properties. The extent of oxidation of the copolymers was determined from the ratio of the oxidation to reduction charge, Q ox /Q red. The use of wide potential range leads to reduced films, whereas the narrow range leads to partially oxidized films. The copolymers exhibit a characteristic band in UV-vis spectra at $ 410 nm, which shifts to higher wavelengths for the more doped material. The electrical conductivity of the copolymers was correlated to their morphology and their structure. The copolymer with higher conductivity is partially reduced, has compact morphology and higher ratio of quinoid to benzenoid rings. The energy gap of the copolymers is reversely proportional to their electrical conductivity. The optical and electrical properties of the copolymers make them very well suited for use as hole transport layers (HTL) in organic opto-electronic devices. We prepared polymer : fullerene solar cells with copolymer HTLs. The solar cell performance was tested with very encouraging initial results. V

Research paper thumbnail of Effect of the acceptor moiety on the electrochemical and electrochromic properties of Donor-Acceptor-Donor polymer films

International Journal of Electrochemical Science, Apr 1, 2015

The aim of this work is to synthesize EC polymers having green or blue colour in the neutral stat... more The aim of this work is to synthesize EC polymers having green or blue colour in the neutral state and transparent oxidized state by using the D-AD approach. Two different monomers, diphenylthienopyrazine (M1) and diphenylquinoxaline (M2) are synthesized. The monomers are successfully electropolymerized to P1 and P2, respectively, by cyclic voltammetry on ITO substrates. The effect of the acceptor moiety on the electrochemical and electrochromic properties of the polymer films is investigated. Both polymers exhibit the characteristic redox couple due to their oxidation/reduction at 0.95 V/0.62 V for P1 and at 1.05 V/0.35 V for P2; their doping/dedoping reaction is reversible. The two polymers have different optical properties; namely, the phenyl ring in the acceptor unit (P2) caused hypsochromic shift. The acceptor moiety affects mainly the LUMO level; specifically, the LUMO level shifted to less negative values by replacing thiophene with phenyl. The electrochromic properties of the polymer films are strongly affected by the acceptor moiety. Polymer P1 changes its colour from green (neutral state), to grey (intermediate oxidised state), to transparent grey/sky blue (oxidized state) and to lemon green (reduced state). Correspondingly, P2 starts from royal blue (neutral state), going to blue purple, grey-blue and light grey (intermediate oxidised states) and then to green (oxidized state); additionally, it became also oil green and light blue (reduced states). Both polymers are multicoloured and were good candidates for application in electrochromic devices.

Research paper thumbnail of Synthesis and characterization of electrically conducting copolymers based on biphenyl and thiophene

Journal of Applied Polymer Science, Jun 3, 2010

ABSTRACT

Research paper thumbnail of Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

Journal of Applied Polymer Science, Oct 5, 2008

ABSTRACT

Research paper thumbnail of Thiophene-Based Copolymers Synthesized by Electropolymerization for Application as Hole Transport Layer in Organic Photovoltaics Cells

Springer eBooks, Oct 16, 2013

Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The... more Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The potential range used has a strong influence on the film structure and properties. The extent of oxidation of the copolymers was determined from the ratio of the oxidation to reduction charge, Q ox /Q red. The use of wide potential range leads to reduced films, whereas the narrow range leads to partially oxidized films. The copolymers exhibit a characteristic band in UV-vis spectra at $ 410 nm, which shifts to higher wavelengths for the more doped material. The electrical conductivity of the copolymers was correlated to their morphology and their structure. The copolymer with higher conductivity is partially reduced, has compact morphology and higher ratio of quinoid to benzenoid rings. The energy gap of the copolymers is reversely proportional to their electrical conductivity. The optical and electrical properties of the copolymers make them very well suited for use as hole transport layers (HTL) in organic opto-electronic devices. We prepared polymer : fullerene solar cells with copolymer HTLs. The solar cell performance was tested with very encouraging initial results. V

Research paper thumbnail of Electrochemical synthesis and characterization of conducting copolymers of biphenyl with pyrrole

Journal of Applied Polymer Science, Jan 18, 2012

The electrochemical oxidation of anodic metal (zinc or cadmium) in acetonitrile solution of the p... more The electrochemical oxidation of anodic metal (zinc or cadmium) in acetonitrile solution of the potentially chelating Schiff base N,N-(dithiodiethylenebis(aminylydenemethylydene)bis(1,2-phenylene)ditosylamide (H 2 L) afforded stable complexes of empirical formula [ML]. The crystal and molecular structures of [ZnL] • CH 3 CN (1) and [CdL] (2) have been determined by X-ray diffraction. In both complexes the metal atom is in a distorted

Research paper thumbnail of Synthesis of Thiophene-Based Copolymers for Application in Dual Layer ECDs

Dual layer electrochromic devices (ECDs) were constructed using copolymers synthesized from elect... more Dual layer electrochromic devices (ECDs) were constructed using copolymers synthesized from electron donor-acceptordonor (D-A-D) monomers with thiophene-based donor moieties. Comonomers having different D-A-D structures were synthesized and successfully electropolymerized as uniform films onto ITO. The properties of the films depended on the acceptor moiety. Compared to the corresponding single layer ECDs, the dual layer devices exhibited genuine multicoloured EC behavior and improved operational characteristics. Further development of the dual layer ECDs is expected to lead towards optimized performance.

Research paper thumbnail of Influence of electrochemical copolymerization conditions of 3-methylthiophene and biphenyl on the morphology and nanomechanical properties of the films

Journal of Applied Polymer Science, 2015

N-Acetyltra change in classificatio the present covered exo identified m Overall, we acetylators ... more N-Acetyltra change in classificatio the present covered exo identified m Overall, we acetylators were found detected in gender diffe

Research paper thumbnail of Structural analysis of biodegradable low-molecular mass copolyesters based on glycolic acid, adipic acid and 1,4 butanediol and correlation with their hydrolytic degradation

Polymer Degradation and Stability, 2012

Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, thei... more Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, their in vitro hydrolytic degradation was studied and correlated with their structure. The hydrolytic degradation of the copolyesters was directly related with the degree of crystallinity and the diameter of the crystallites. It was found that glycolate units disturb the ordering of the butylene adipate units, which results in a decrease of the crystallinity. By comparing the hydrolysis parameters of synthesized copolyesters with those of similar aliphatic copolyesters a hydrolysis mechanism was proposed. According to this mechanism, the degradation takes place not only by the loss of end units, but also through the removal of larger segments. MALDI-TOF MS data showed that the possibility of a copolyester macromolecule forming cyclic structures correlates with the arrangement of ester groups in the macromolecules and the structure of the linear segments.

Research paper thumbnail of Synthesis of Copolymers Based on Benzene and Biphenyl and their Characterization by XRD and DSC

Journal of Research Updates in Polymer Science, 2012

In this work the crystalinity and the thermal transitions of soluble and insoluble in chlorobenze... more In this work the crystalinity and the thermal transitions of soluble and insoluble in chlorobenzene polyphenylene copolymers (synthesized by oxidative cationic polymerization) were studied. All copolymers had a degree of crystallinity between 44.6 and 66.7 %. With Differential Scanning Calorimentry (DSC) measurements it was found that the copolymers exhibited endothermic peaks in the region 268 up to 286 oC. These peaks in the case of soluble polyphenylenes were attributed to the melting of their crystallites, whereas in the case of insoluble polyphenylenes were attributed to liquid crystal transitions.

Research paper thumbnail of Ηλεκτρικά αγώγιμα συμπολυμερή βάσεως πολυφαινυλενίων

Research paper thumbnail of Synthesis and characterization of hydrolytically degradable copolyester biomaterials based on glycolic acid, sebacic acid and ethylene glycol

Journal of Materials Science: Materials in Medicine, 2011

Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthes... more Copolyesters of glycolic acid (G) combined with sebacic acid (S) and ethylene glycol were synthesized in different molar ratios (G: 0-100% and S: 100-0%) and their hydrolytic degradation was studied and correlated with their structures. Based on the FTIR spectra of the homopolyesters and copolyesters and the normalized peak intensity of the I 2918 , I 2848 and I 1087 for the corresponding wavenumbers, it is concluded that the I 2918 and the I 2848 are in accordance with the mean number degree of polymerization of ethylene sebacate units and the I 1087 is in accordance with the mean number degree of polymerization of glycolate units. Based on the XRD diffractograms, poly(ethylene sebacate) and poly(glycolic acid) belong to the monoclinic and the orthorhombic crystal system, respectively and both have higher crystallinity than the copolyesters. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model and fourparameter model. Three regions can been distinguished for the hydrolytic degradation by decreasing the molar feed ratio of sebacic acid, which are correlated with the changes of crystallinity. Two copolyesters are proposed: first the copolyester with high amount of glycolate units (S10G90) having higher hydrolytic degradation than G100 and second the copolyester with equal amount of glycolate and ethylene sebacate units (S50G50), having lower hydrolytic degradation than G100. These hydrolytically degradable copolyesters are soluble in common organic solvents, opposite to poly(glycolic acid) and could have perspectives for biomedical applications.

Research paper thumbnail of Correlation of hydrolytic degradation with structure for copolyesters produced from glycolic and adipic acids

Journal of Materials Science: Materials in Medicine, 2009

Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) wer... more Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100-50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm-1 can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm-1 due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm-1 due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.

Research paper thumbnail of Electrochemical grafting of 4-phenoxybenzoic acid units onto oxidized carbon fibers as a first step for high temperature composites

Journal of Applied Polymer Science, 2013

The electropolymerization of 4-phenoxybenzoic acid (4-PBA) onto carbon fibers (CFs) was studied a... more The electropolymerization of 4-phenoxybenzoic acid (4-PBA) onto carbon fibers (CFs) was studied as a way to synthesize coated CFs with grafted poly(para-phenyl ether ketone) (p-PEK) and enhance their wettability by matrices such as PEK or PEEK. Since the pristine CFs were not electrochemically active enough, a proper electrochemical oxidation treatment using sulfuric acid was applied, capable of creating oxygen-containing groups onto their surface. The groups formed in the oxidized CFs were electron acceptors and their amount was quasi-quantitatively evaluated based on their ability to absorb dye from aqueous solutions. The graft electropolymerization of 4-PBA onto the CFs electrode was achieved at anodic potentials using cyclic voltammetry (CV). The grafted coating had a thickness of up to 0.35 lm. The materials were characterized using FTIR, NMR, SEM, and TGA. A possible reaction mechanism is proposed, for the grafting of 4-PBA units onto the carboxyl groups of the treated CFs. The coated CFs were more thermally stable compared to the treated CFs without grafting.

Research paper thumbnail of Influence of backbone rigidity on the curing and the dielectric relaxations of unsaturated polyesters

Journal of Applied Polymer Science, 2010

ABSTRACT

Research paper thumbnail of Electrical conductivity and mechanical strength of composites consisting of phenolic resin, carbon fibers, and metal particles

Journal of Applied Polymer Science, 2011

Composites of phenolic resin of novolac type as matrix, with metal particles of Zn as conducting ... more Composites of phenolic resin of novolac type as matrix, with metal particles of Zn as conducting filler, without or with 15% v/v carbon fibers were manufactured by hot pressing. The porosity ratio, the hardness, the flexural and shear strength, and the electrical conductivity of the composites were determined. The percolation threshold was determined based on two models of electrical conductivity versus the content of metal particles of Zn, namely, an analogous to polymer gelation model and the other based on the power law. The composites of carbon fibers combined with Zn particles have higher electrical conductivity than the corresponding without carbon fibers and high strength, lower than that of the composite reinforced with carbon fibers without Zn particles, but still acceptable.

Research paper thumbnail of Thiophene-based copolymers synthesized by electropolymerization for application as hole transport layer in organic solar cells

Journal of Applied Polymer Science, 2012

Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The... more Electrically conducting thiophene-based copolymers were synthesized by electropolymerization. The potential range used has a strong influence on the film structure and properties. The extent of oxidation of the copolymers was determined from the ratio of the oxidation to reduction charge, Q ox /Q red. The use of wide potential range leads to reduced films, whereas the narrow range leads to partially oxidized films. The copolymers exhibit a characteristic band in UV-vis spectra at $ 410 nm, which shifts to higher wavelengths for the more doped material. The electrical conductivity of the copolymers was correlated to their morphology and their structure. The copolymer with higher conductivity is partially reduced, has compact morphology and higher ratio of quinoid to benzenoid rings. The energy gap of the copolymers is reversely proportional to their electrical conductivity. The optical and electrical properties of the copolymers make them very well suited for use as hole transport layers (HTL) in organic opto-electronic devices. We prepared polymer : fullerene solar cells with copolymer HTLs. The solar cell performance was tested with very encouraging initial results. V