Doped poly (2,5‐dimethyl aniline) for the detection of ethanol

Poly (2,5‐dimethyl aniline) (P25DMA), with and without NiO and ZnO as dopants, is evaluated as a sensing material for ethanol to detect transdermal ethanol emissions. Three sensing materials—P25DMA, P25DMA doped with 20 wt % NiO, and P25DMA doped with 20 wt % ZnO—are eventually deposited onto a radio frequency identification sensor. The limit of detection for the materials is found to be 3, 24, and 420 ppm, respectively. Also, all three sensing materials are selective toward ethanol with benzene and methanol used as interferents. The response and recovery times are also measured for the three sensing materials and are in the order of seconds, which is acceptable for a transdermal ethanol sensor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42259.     

Spectroelectrochemical study of a soluble derivative of poly(aniline) in a room temperature ionic liquid

Poly(phenylene sulfide phenyleneamine), PPSA, is a soluble copolymer of poly(aniline) and poly(phenylene sulfide). Its electrochemical behavior has already been studied in both aqueous and organic media in the presence of different electrolytes, where it was observed the loss of electroactivity after few cycles. In this paper, the spectroelectrochemical characterization of PPSA films in a room temperature ionic liquid (RTIL), 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanes sulfonyl)imide (BMMITFSI), is shown. The electrochemical response of a PPSA modified electrode in BMMITFSI is different from that obtained in organic solvent/salt systems. In RTIL, two reversible redox processes were observed and they were assigned to the reversible radical cation/dication transition based on “in situ” UV-vis and Raman spectroscopic studies. The stabilization of the dicationic species in RTIL is an explanation for the reversible electrochemical response of the PPSA in BMMITFSI; on the contrary, when the electrochemical oxidation is carried out in conventional organic electrolytes, once the oxidation of the sulfur atom occurs, a loss of electroactivity is observed being not possible to recover the pristine state of the polymer. FTIR and XRD data obtained for the fully oxidized polymer in acetonitrile are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the activated aromatic rings. It is not the case in RTIL due to the shielding of the charged sulfur atoms avoiding its reaction to other chains to form the networked polymeric matrix.     

Photoemission and conductivity measurement of poly(N‐methyl aniline) and poly(N‐ethyl aniline) films

The studies involve the X‐ray photoelectron spectroscopy (XPS) and conductivity measurements of poly(N‐methyl aniline) and poly(N‐ethyl aniline) films deposited electrochemically at different pH values of −0.96, 2.22, and 3.78 for N‐methyl aniline and 1.10, 2.22, and 3.78 for N‐ethyl aniline. The results obtained reveal significant differences in the film properties of the two matrices as a function of pH of solution. These differences are explained on the basis of the competitive reaction products formed during polymerization in the two matrices along with the differences in the electron‐donating ability of the methyl and ethyl groups present on the nitrogen (N) atom. These results are further supported by the UV–Visible and IR data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1286–1292, 1999     

Evaluation of polyesters from renewable resources as alternatives to the current fossil-based polymers. Phase transitions of poly(butylene 2,5-furan-dicarboxylate)

Poly(butylene 2,5-furan dicarboxylate) (PBF) is an alipharomatic polyester that can be prepared using monomers derived from renewable resources such as 2,5-furan dicarboxylic acid and 1,4-butanediol. In the present work the thermal behavior of PBF was studied. Multiple melting was observed during heating traces of samples isothermally crystallized from the melt using differential scanning calorimetry (DSC). The wide angle X-ray diffraction (WAXD) patterns did not reveal the presence of a second crystal population, or a crystal transition upon heating. DSC study showed that the phenomena are closely related to recrystallization. Temperature modulated DSC (TMDSC) tests indeed evidenced enhanced recrystallization. The equilibrium melting point was estimated to be 184.5 °C using the linear Hoffman–Weeks extrapolation. The heat of fusion of the pure crystalline polymer was found equal to 129 J/g or (27.35 kJ/mol), a little lower than that of PBT. The Lauritzen–Hoffman secondary nucleation theory was used and the surface energy values and the work of chain folding were found to be comparable to those of PBT, but quite lower than those of poly(ethylene terephthalate) (PET). The non-isothermal crystallization on cooling and the cold-crystallization of quenched samples were also studied. Condensed spherulites were observed on isothermal crystallization under large supercoolings by using polarized optical microscopy (POM), while the spherulites turned to ring-banded morphology at higher temperatures. In every case the nucleation density was high.     

Corrosion protective poly(o-ethoxyaniline) coatings on copper

Poly(o-ethoxyaniline) (POEA) coatings were synthesized on copper (Cu) by electrochemical polymerization of o-ethoxyaniline in aqueous salicylate solution by using cyclic voltammetry. These coatings were characterized by cyclic voltammetry, UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The performance of POEA as protective coating against corrosion of Cu in aqueous 3% NaCl was assessed by the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results of the potentiodynamic polarization and EIS studies demonstrate that the POEA coating has ability to protect the Cu against corrosion. The corrosion potential was about 0.330 V versus SCE more positive in aqueous 3% NaCl for the POEA coated Cu than that of uncoated Cu and reduces the corrosion rate of Cu almost by a factor of 140.     

Blends of poly(ethylene oxide) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate): thermal analysis, morphological behaviour and specific interactions

DSC and optical microscopy were used to determine the miscibility and crystallinity of blends of poly(ethylene oxide) (PEO) with poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM). A single glass transition temperature was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the size of the PEO spherullites is observed, as PVPh-HEM is added. FTIR was used to probe the intermolecular specific interactions of the blends and the miscibility of the blend is mainly attributed to PVPh-HEM/PEO intermolecular interactions via hydrogen bonding.     

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV-vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.     

Study on the Crystallization Kinetic and Characterization of Poly(lactic acid) and Poly(vinyl alcohol) Blends

In this study, poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) blends, with PLA/PVA mass ratios of 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60, were prepared by means of the melt blending method. The result of torque measurements and thermal gravimtric analysis tests showed that the addition of PLA can decrease the melt viscosity of PVA and that the second degradation step of PVA nearly disappeared for the PLA₈₀/PVA₂₀ blend. The absorbance peaks of the carbonyl group and the hydroxyl group in the Fourier transform infrared spectra of PLA/PVA blends had significant shifts to lower wave numbers, indicating that there were interactions between these two groups. Combined with the result of the differential scanning calorimetry curves, this interaction would be favorable for improving miscibility. The X-ray diffraction patterns and the polarized light microscope (PLM) micrographs showed that PVA can serve as a nucleating agent to promote the crystallization of PLA in PLA/PVA blends. Moreover, the PLA₈₀/PVA₂₀ blend gave the highest growth rate of PLA spherulite.     

Self-assembly of cationic rod-like poly(2,5-pyridine) by acidic bis(trifluoromethane)sulfonimide in the hydrated state: A highly-ordered self-assembled protonic conductor

We show that acid-base complexation of rod-like poly(2,5-pyridine) (PPY) by bis(trifluoromethane)sulfonimide (TFSI) leads to highly-ordered lamellar self-assemblies in the hydrated films and shows relatively high room temperature conductivity of ca. 10⁻⁴ S/cm. Thin films with different nominal degrees of complexation were studied using X-ray diffraction, Fourier transform infrared spectroscopy, contact angle measurements, conductivity measurements, and polarised optical microscopy. We propose that the self-assembly is promoted by the amphiphilicity of TFSI and the interplay between the hydrophilic and hydrophobic sites within the complexes. The hydrophilic sites allow confinement of water molecules within the hydrated self-assemblies for low loading of TFSI to promote proton conductivity. For high loading of TFSI in the hydrated state, another coincident self-assembled structure is additionally observed, which we suggest to form due to phase separated water/TFSI domains, as resembling lamellar water/surfactant liquid crystalline phases. The new type of self-assembled acid-base material combining rod-like polymeric cations and ionic liquid anions suggests new routes for ionic and protonic transport and functional materials.     

Investigation on the microstructure and the electric property of poly(propylene)/chlorinated poly(propylene)/poly(aniline) composites

The article presents results of studies on composites made from poly(propylene) (PP) modified with poly(aniline) (PANI) doped with dodecylbenzene sulfonic acid (DBSA) and chlorinated poly(propylene) (CPP). The volume resistivity of PP/CPP/PANI composites was detected, and the results show that the volume resistivity decreases with increasing CPP content, and there exists a minimum volume resistivity. Effects of CPP on the microstructure and crystalline structure of the PP/CPP/PANI composites and the relationship between the effects and the electric property were carefully analyzed by scanning electron microscope (SEM) and wide angle X‐ray diffraction (WAXD). The method that the specimens of SEM are polished is appropriate to investigate the morphology of conducting polymer composites. The obtained results illuminate that the area of conducting parts and insulating parts obtained from the digital analysis of the SEM image is obviously influenced by the CPP content, the parameters of the lamellar‐like structure are immediately related to CPP content and denote the dispersion of PANI‐DBSA, and the percent crystallinity and mean crystal size of PP are directly correlated with the CPP content. The increasing area of conducting parts, the increasement of layer distance, the decreasement of size and layer number of the lamellar‐like structure of PANI‐DBSA, and the increasement of the percent crystallinity and mean crystal size of PP are beneficial to the improvement of the conductive property of PP/CPP/PANI composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Clickable,versatile poly(2,5-dithienylpyrrole) derivatives

In this study a novel, clickable, azide containing conducting polymers based on 1-(2-azido-ethyl)-2,5-dithiophene-2-yl-1H-pyrrole (SNS-N₃) were synthesized and characterized. Optical and electronic properties of homopolymer (PSNS-N₃) were investigated and colorimetric studies were performed. The homopolymer has a band gap of 2.49 eV and it displays yellow to blue coloration upon doping. Electrochemically prepared copolymers of SNS-N₃ and 3,4-ethylenedioxythiophene (EDOT) formed multichromic, color tunable electrochromic materials with continuous color gradient from cinnamon, mustard, lime green, blue and dark blue. Spectroelectrochemical analyses revealed that the neutral copolymers possess two absorption maxima (～320 and 450 nm) where the relative intensity and position of the two depends on polymerization potential. Copolymer films could be fully switched between their neutral and oxidized forms in ～1.2 s with a percent transmittance of ～65% at 950 nm. Moreover, a PSNS-N₃ coated ITO electrode was subjected to click reaction using ethynylferrocene. CV and FTIR studies revealed that ferrocene could easily be attached onto the electrode surface without loss of electroactivity of both ferrocene and PSNS backbone. Our results suggest that electrochemically prepared PSNS-N₃ films offer a novel and multipurpose platform for simple, effective post-functionalization of poly(2,5-dithienylpyrrole)s under mild conditions.     

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

Poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) were chosen to prepare polymer complex and blends. The complex was prepared from ethanol solution and the blends were prepared from 1-methyl-2-pyrrolidone solution. DSC results show that the T_gs of the PAA/PVP blends lie between those of the two constituent polymers, whereas T_g of the PAA/PVP complex is higher than both blends and the two constituent polymers. TGA results show that degradation temperature, T_d, of PAA increases upon adding PVP in the blend, but thermal stability of the complex is higher than that of the blends as reflected by the higher T_d. Both FTIR and high-resolution solid state NMR show strong hydrogen bonding between PAA and PVP by showing significant chemical shift. The T_1ρ(H) measurement shows that the homogeneity scale for the blend is at ∼20 Å and that for the complex is ∼15 Å.     

Studies of electrochemically deposited poly(N-methyl aniline) films

The effect of surface resistance of substrate and concentration of monomer on the properties of electrochemically deposited poly(N-methyl aniline) films has been investigated. The UV–visible spectra of the films show enhanced selectivity in the formation of the conducting phase (approximately 860nm) of polymer on lower surface resistance substrate (10Ω/□) over those with higher surface resistance (50Ω/□). The magnitude of selectivity increases with concentration of monomer. These results are further supported by IR analysis of the samples. From morphological studies it is noted that the films deposited on 10Ω/□ substrates exhibit an overall granular nature irrespective of concentration of monomer. In the case of films deposited on 50Ω/□ substrates sequential changes in patterning are observed with increasing concentration of monomer. Two redox couples are observed in the cyclic voltammograms together with distortion of peak potential in the films obtained on higher surface resistance substrates. © SCI 1998.     

Corrosion inhibition by poly(N-ethylaniline) coatings of mild steel in aqueous acidic solutions

Poly(N-ethylaniline) (PNEA) coatings on mild steel have been electrodeposited from 0.1 to 0.5 M aqueous oxalic acid solutions containing 0.1 M N-ethylaniline (NEA) using potentiodynamic synthesis technique. The effect of oxalic acid concentration on the corrosion behavior of PNEA coated mild steel surfaces were investigated by DC polarization and electrochemical impedance spectroscopy (EIS) techniques in 0.1 M HCl and 0.05 M H₂SO₄ solutions. Corrosion test results showed that corrosion resistance of PNEA coatings decreases with increasing concentrations of oxalic acid in polymerization solution. Decreasing acidity of the polymerization solution causes more effective protection against corrosion in aqueous acidic corrosive medium.     

Influence of intramolecular specific interactions on phase behavior of epoxy resin and poly(ε-caprolactone) blends cured with aromatic amines

Two aromatic amines were used as the curing agents to prepare the thermosetting blends of epoxy and poly(ε-caprolactone) (PCL). When cured with 4,4′-methylenebis(2-chloroaniline) (MOCA), the thermosetting blends are miscible in the amorphous state in the entire composition, which was evidenced by the behavior of single, and composition-dependent glass transition temperatures (T_g's) in terms of thermal analysis. Fourier transform infrared spectroscopy (FTIR) showed that there are the intermolecular specific interactions (viz. hydrogen bonding) between the component polymers. However, the 4,4′-diaminodiphenylsulfone (DDS)-cured epoxy forms the immiscible blends with PCL. The blends displayed a typical reaction-induced phase separation morphology. The phase behavior seems to be more than the expected since it was ever proposed that there would be the intermolecular specific interactions between amine-cured epoxy and PCL, which would fulfill the miscibility of the systems. To interpret the phase behavior, we investigated that the miscibility and intermolecular specific interactions in the blends of model compounds and linear homologues of epoxy with PCL. It was observed that in MOCA-cured blends there were much stronger intermolecular specific interactions than in DDS-cured counterparts. The weaker intermolecular specific interactions between DDS-cured epoxy and PCL resulted from the formation of the intramolecular hydrogen bonding interactions within DDS-crosslinked epoxy, which were involved with the sulfonyl groups and the secondary hydroxyls. The intramolecular association could suppress the formation of the strong intermolecular hydrogen bonding interactions between carbonyls and hydroxyls of amine-cured epoxy, which are sufficient to fulfill the homogenization of the system during the in situ polymerization. Therefore, the presence of the intramolecular specific interactions between sulfonyl and hydroxyl groups was taken as the origin of phase-separated morphology for DDS-cured blends of epoxy with PCL.     

Dynamic mechanical and tensile properties of poly(N-vinyl pyrrolidone)-poly(ethylene glycol) blends

Mechanical properties of miscible blends of high molecular weight poly(N-vinyl pyrrolidone) (PVP) with a short-chain, liquid poly(ethylene glycol) (PEG) of molecular weight 400 g/mol have been examined as a function of PVP-PEG composition and degree of hydration. The small-strain behavior in the linear elastic region has been evaluated with the dynamic mechanical analysis and compared with the viscoelastic behavior of PVP-PEG blends under large strains in the course of uniaxial drawing to fracture and under cyclic extension. A strong decoupling between the small-strain and the large strain properties of the blends has been observed, indicative of a pronounced deviation from rubber elasticity in the behavior of the blends. This deviation, also seen on tensile tests under fast drawing, is attributed to the peculiar phase behavior of the blends and the molecular mechanism of PVP-PEG interaction. Nevertheless, for the PVP blend with 36% PEG, under comparatively low extension rates, the reversible contribution to the total work of deformation up to ε=300% has been found to be maximum at around 70%, while the blends containing 31 and 41% PEG behave rather as an elastic-plastic solid and a viscoelastic liquid, respectively.     

Morphology and Dielectric Properties of Polyhydroxybutyrate (PHB)/Poly(methylmethacrylate)(PMMA) Blends with Some Antimicrobial Applications

Poly(3-hydroxy)butyrate (PHB) is a microbial polyester, which provides the advantages of biodegradability and biocompatibility but it is brittle and has low abilities for some chemical modifications. To overcome such problems reactive blending was done with a glassy acrylic polymer, poly(methylmethacrylate) (PMMA) with different compositions. The dielectric response of PHB/PMMA blend with different compositions were investigated as a function of frequency and at different temperatures. The results revealed the existence of single a-relaxation process indicating the miscibility of amorphous fractions of PHB and PMMA. Also the morphological study of such blends doesn't show macro phase separation of PMMA on the surface scan which may be attributed to the compatibility in melt between PHB and PMMA particles in the PHB matrix. The biological activity of such investigated systems against some pathogenic microorganisms was found to increase by increasing the amount of PMMA in the blend     

Electrochemical synthesis of a novel poly(2,5-dimethoxy aniline) nanorod for ultrasensitive glucose biosensor application

We report for the first time a rapid electrochemical synthesis of one-dimensional poly(2,5-dimethoxyaniline) nanorods (PDMA-NR) in the presence of surfactant. FE-SEM and TEM images confirm the PDMA-NR formation and the average diameter of single rod sizes in the range of ∼200–300 nm. An enzymatic glucose biosensor was fabricated through immobilizing glucose oxidase (GOx) into PDMA-NR matrix. The amperometric current response of PDMA-NR/GOx to glucose is linear in the concentration range between 1 and 10 μM with a detection limit of 0.5 μM (S/N = 3). The PDMA-NR/GOx electrode possesses high sensitivity (5.03 μA/μM), selectivity, stability, and reproducibility toward glucose.     

Electropolymerized bilayer coatings of polyaniline and poly(N-methylaniline) on mild steel and their corrosion protection performance

Polyaniline (PANI) and poly(N-methylaniline) (PNMA) have been electrodeposited on mild steel from oxalic acid bath using cyclic voltammetric technique. Pretreatments like passivation and primer polymer coatings were required for effective coating. Differently stacked composite polymer layers on the metal surface by layer-by-layer approach have also been obtained and their properties have been compared with their corresponding copolymer coatings. FTIR study confirms the formation of electroactive polymer compounds on mild steel. Evaluation of these coatings in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy reveals significant corrosion resistant behavior. Relatively higher corrosion protection is exhibited by copolymer coatings and composite-bilayer coatings than the corresponding homopolymer coatings. The composite metal–PANI–PNMA layer shows higher stability and better protection than the metal–PNMA–PANI layer.