Conducting SBS block copolymer–polyaniline blends prepared by mechanical mixing

Polyaniline was doped with dodecylbenzenesulfonic acid (Pani · DBSA) in an agate mortar and used as a conductive additive in melt blends with styrene–butadiene–styrene (SBS) block copolymer. These blends exhibit relatively high levels of electrical conductivity at low‐weight fractions of the polyaniline complex. The melt blending process, performed in a two‐roll mill or in a Haake internal mixer, increased the protonation degree of the Pani · DBSA, as indicated by X‐ray photoelectron spectroscopy analysis. This result confirms the occurrence of a second doping process at high temperature. The mechanical performance decreases as the amount of Pani · DBSA in the blend increases, indicating a plasticizing effect of the DBSA. The higher temperature used in blending imparts better conductivity value but gives rise to a strong crosslinked material because of the presence of the sulfonic acid and the high extent of double bonds in the SBS compound. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 626–633, 2001     

Influence of plasticizers (DOP and CNSL) on mechanical and electrical properties of SBS/polyaniline blends

Electrically conductive blends based on polyaniline-dodecylbenzene sulfonic acid (Pani.DBSA)/styrene-butadiene-styrene (SBS) block copolymer have been prepared in the presence of different plasticizers such as dioctyl phthalate (DOP) and cashew nut shell liquid (CNSL). The products were characterized by ultraviolet-visible (UV-vis) spectrometry, scanning electron microscopy, X-ray diffraction, electron paramagnetic resonance (EPR) and resistivity measurements. The presence of DOP resulted in an increase of the electrical resistivity whereas the increasing concentration of CNSL resulted in a decrease of electrical resistivity. In the latter case, the presence of cardanol, a phenol-type compound in CNSL, may be responsible for the improved electrical performance, probably because of a secondary doping process, which changes the molecular conformation of Pani.DBSA chains from “compact coil” to “expanded coil”. In addition, CNSL contributes to the formation of cocontinuous-type morphology with conducting pathways in larger extension. EPR studies also showed an increase of the polaron mobility as the amount of CNSL in the blend increases.     

Studies on dynamically vulcanized polypropylene (PP)/butadiene styrene block copolymer (SBS) blends: Crystallization and thermal behavior

Crystallization of polypropylene (PP) in unvulcanized blends of PP with the butadiene–styrene block copolymer (SBS) was studied through differential scanning calorimetry (DSC) and X‐ray diffraction measurements in the composition range of 0–40 wt % SBS content. Analysis of the crystallization exotherms revealed variation in the crystallization behavior, crystallinity, and crystalline morphology of the PP component in the blends at various levels of SBS concentration. The crystallinity determined by X‐ray diffraction and DSC showed identical variations with the blend composition. The tensile and thermal properties of the blends were studied in the entire composition range. Correlations of the tensile properties with the crystallization parameters of the PP component in the blends are also presented. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 151–161, 1999     

Studies on the dynamically vulcanized polypropylene (PP)/butadiene styrene block copolymer (SBS) blends: Mechanical properties

Unvulcanized and dynamically vulcanized blends of isotactic polypropylene (PP) and butadiene styrene block copolymer (SBS) in the composition range of 10–40 wt % SBS were prepared by melt mixing in an internal mixer and evaluated for impact and tensile properties. Dynamic vulcanization of blends gave superior mechanical properties. Systematic changes with varying blend composition were found in stress-strain behavior in both the blend systems. The effect of blend composition on the state of dispersion and morphology of the dispersed phase droplets were studied by scanning electron microscopy. Analysis of the yield stress data in terms of various theoretical models revealed the variation of stress concentration effect with blend composition and higher interphase adhesion in dynamically vulcanized blends. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2691–2701, 1997     

Dynamic mechanical properties of polycarbonate and acrylonitrile–butadiene–styrene copolymer blends

Blends of polycarbonate (PC) and poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) with different compositions are characterized by means of dynamic mechanical measurements. The samples show phase separation. The shift in the temperatures of the main dynamic mechanical relaxation shown by the blend with respect to those of the pure components is attributed to the migration of oligomers present in the ABS toward the PC in the melt blending process. A comparison with other techniques (dielectric and calorimetric analysis) and the application of the Takayanagi three block model confirm this hypothesis. In all the studied blend compositions (ABS weight up to 28.6%) the PC appears as the matrix where a disperse phase of ABS is present. The scanning and transmission electron microscopy micrographs show that the size of the ABS particles increases when the proportion of ABS in the blend increases. The FTIR results indicate that the interaction between both components are nonpolar in nature and can be enhanced by the preparation procedure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1507–1516, 2002     

Networks and blends of polyaniline and polyurethane: correlations between composition and thermal, dynamic mechanical and electrical properties

The combination of the electrical conducting properties of polyaniline (Pani) with the mechanical performance of polyurethanes (PU) was accomplished through the interconnection of the two polymers via condensation of a NCO terminated PU prepolymer and the amine groups of polyaniline. The crosslinking density of the resulting networks was set by the proportion between the two components, since the PU length was kept constant (M_w=40,000, M_n=23,000). The composition range Pani/PU spanned from 1 to 30%. Blends of the same composition were prepared for comparison purposes. Taking into account the IR absorption shifts, DMTA spectra, electrical conductivity results and computer generated optimized chain conformation, a morphological interpretation is proposed in which Pani chains form a continuous percolating phase dispersed in a polyurethane matrix, linked together by an interphase, with a certain degree of miscibility. This interphase would be responsible for the connectivity between the two components and the good mechanical properties observed. Electrical conductivity of the networks was in the 10⁻⁴ S/cm range.     

Relations between molecular mixing state and conductive property in blends composed of polyaniline and aliphatic copolymer having acid groups

Blend films composed of polyaniline and aliphatic copolymer having carboxylic acid groups were prepared by vaporizing a solvent from a solution of both polymers. Poly(methyl methacrylate‐co‐methacrylic acid) and poly(1‐vinylpyrrolidone‐co‐acrylic acid) were used as the copolymers in this work. Conductivity of the blend film increased with decreasing concentration of polyaniline and then decreased in the region of low concentration. The N_1s peak in the ESCA spectrum of the blend film was shifted to higher binding energy with decreasing concentration of polyaniline and then was done to lower the binding energy in the region of low concentration. Polyaniline chains in the blend films become conductive by being oxidized with the carboxylic acid groups, which are the constituents of the copolymers. Through strong intermolecular interactions such as ionic bonding and hydrogen bonding between polyaniline and the copolymer, densities of the blend films are always higher than those predicted on the basis of the additive law. Blend films with higher density and higher conductivity are able to be prepared with a higher vaporizing rate, given that phase separation occurring during vaporizing process can be depressed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1113–1117, 2002     

Rheological and mechanical properties of PEO/block copolymer blends

Small quantities of block copolymers from two families, styrene‐butadiene‐methylmethacrylate (SBM) and methylmethacrylate‐butylacrylate‐methylmethacrylate (MAM) have been added to a polyethylene oxide (PEO) in order to improve its processability, namely increasing its elastic modulus without increasing too much its shear viscosity. The copolymers contain one block of polymethylmethacrylate (PMMA) that is compatible with PEO; the other blocks create nano phases, dispersed in the PEO matrix. Considerable efforts were devoted to finding the best blending method, either melt processing or solution casting. PEO is very sensitive to shear, and was found to degrade both in the bulk and in solution. Degradation, which cannot be avoided, was quantified through intrinsic viscosity measurements. The rheological characterization of blends containing 1, 2, and 5 wt% block copolymer was carried out. The elastic modulus was found to increase more than the complex viscosity. Blends obtained by solution casting technique gave better results. The elongational viscosity obtained for one blend containing 5 wt% of SBM showed a slight increase with respect to the pure PEO. Mechanical properties were then investigated, through tensile tests and dynamic mechanical analysis in flexion and in torsion; the copolymer generally enhanced the mechanical properties. POLYM. ENG. SCI., 45:1385–1394, 2005. © 2005 Society of Plastics Engineers     

Effects of arm number on the properties of transparent elastomers prepared from styrene–butadiene block copolymer

A series of the SBS transparent elastomers were prepared from star‐shaped SBS having different arm number by solution‐casting. Their structure and physical properties were characterized by scanning electron microscope, ultraviolet spectrometer, wide‐angle X‐ray diffractometer, differential scanning calorimetry, dynamic mechanical thermal analysis, tensile testing, and contact angle measurements. The results revealed that the miscibility, optical transparence (T_r), tensile strength (σ_b), elongation at break (ε_b), and elasticity at low temperature of the star SBS increased with an increase of arm number. The six‐arm SBS having relatively high molecular weight exhibited a simultaneous enhancement of T_r (90% at 800 nm), σ_b (6.0 Mpa), and ε_b (1260%). This indicated that the SBS materials having six arms had higher transparence and elasticity than others. Moreover, the water contact angle on surface of the star‐shaped SBS film increased with an increase of arm number that is enhancement of hydrophobicity. Therefore, the relatively high arm number and molecular weight played an important role in the improvement of the miscibility and properties of the SBS sheets as a result of the compacted architecture of the hyperbranched molecules. This work provides a convenient way to obtain materials with both high transparence and elasticity by increasing the arm number. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 729–736, 2006     

Comparative study of polyaniline cast films prepared from enzymatically and chemically synthesized polyaniline

Enzymatically and chemically synthesized polyaniline (Pani) were used to prepare free standing cast films from N-methyl-2-pyrrolidinone solutions. The films were redoped by immersion in hydrochloric or p-toluensulfonic acid solutions. Physical and chemical properties were investigated using UV-visible, Fourier transform Infrared and X-ray photoelectron (XPS) spectroscopic techniques. Analysis by XPS revealed changes in the -N/NH- ratio that indicate cross-linking in the surface of both types of films, whereas FT-IR indicates cross-linking in the core of films prepared with enzymatically synthesized Pani. Such changes can be attributed to the catalyzing effect of sulfonic residues and chain defects of the polymer. Consequently, the degree of doping of the films prepared with enzymatically synthesized Pani was lower compared to films prepared with chemically synthesized Pani.     

Miscibility study of polycarbonate and SBS triblock copolymer blends

Polymer blends of Polycarbonate (PC) and Styrene-Butadiene-Styrene triblock (SBS) have been investigated. SBS copolymers have four different styrenic contents, three of which are linear SBS. PC and PS blends are partially miscible as revealed by dynamic mechanical analysis with two clear Tgs near 100–150°C. On the contrary, PC/SBS blends have only one Tg with a left shoulder. Based on the PS domain model of pure SBS, we suggest a micelle model based on the structure when the micelle and absorb PC in the PC/SBS blends. The micelle plays an important role in improving the miscibility. The proposed micelle model has been empolyed to interpret the testing results, such as toughness, impact strength, dynamic mechanical property and SEM morphologies. This proposed micelle model seems a worth-while method to explain the properties of partialtly miscible blends of PC and SBS.     

Blends of styrene butadiene styrene TRI block copolymer/polyaniline-Characterization by WAXS

Electrically conductive blends based on polyaniline-dodecylbenzene sulphonic acid (Pani.DBSA)/styrene-butadiene-styrene (SBS) block copolymer have been prepared by two methods namely melt mixing and polymerization of aniline in the presence of SBS using in situ polymerization method. The influence of composition and synthetic methods on the performance of SBS/Pani blends was established. The obtained SBS/Pani blends have been characterized by mechanical, morphological and electrical properties. A great reduction in volume resistivity values with increase in Pani content was noticed for in situ polymerization method compared to melt mixing method. The microstructural parameters were also computed using Wide Angle X-ray Scattering (WAXS). The results are compared with mechanical and electrical properties.     

Physicomechanical and dielectric properties of magnesium and barium ionomers based on sulfonated maleated styrene‐ethylene/butylene‐styrene block copolymer

Ionomers, containing both carboxylate and sulfonate anions on the polymer backbone, based on metal cations like Mg⁺² and Ba⁺² were prepared by sulfonating maleated styrene‐ethylene/butylene‐styrene block copolymer, hereafter referred to as m‐SEBS, followed by its neutralization by metal acetates. Infrared spectroscopic studies reveal that sulfonation reaction takes place in the para position of the benzene rings of polystyrene blocks and metal salts are formed on neutralization of the precursor acids. Dynamic mechanical thermal analyses show that sulfonation causes increase in T_g of the rubbery phase of m‐SEBS and decrease in tan δ at T_g of the hard phase, along with formation of a rubbery plateau. The changes become more pronounced on neutralization of the sulfonated maleated SEBS, and the effect is greater in the case of Ba salt. Dielectric thermal analyses (DETA) show that incorporation of ionic groups causes profound changes in the dielectric constant (ϵ′) of m‐SEBS. In addition to the low temperature glass–rubber transition, the plot of ϵ′ vs. temperature shows occurrence of a high‐temperature transition, also known as the ionic transition. Activation energy for the dielectric relaxation could be determined on the basis of frequency dependence of the ionic transition temperature. Two values of the activation energy for the dielectric relaxation refer to the presence of two types of ionic aggregates, namely multiplets and clusters. Incorporation of the ionic groups causes enhancement in stress–strain properties as well as retention of the properties at elevated temperatures (50° and 75°C), and the effect is more pronounced in the case of Ba ionomer. Although sulfonated ionomers show greater strength than the carboxylated ionomers, the sulfonated maleated ionomers show higher stress–strain properties in comparison to both sulfonated and carboxylated ionomers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 816–825, 2000     

Galvanic coupling between metal substrate and polyaniline acrylic blends: corrosion protection mechanism

Coating strategies for corrosion protection based on intrinsically electronic conducting polymers, become an important research field mainly due to restrictions to the use of heavy metals, which are related to environmental problems. This work presents the corrosion protection behavior of different metals by using coatings based on acrylic blends formed by polyaniline and poly(methyl methacrylate). Raman spectroscopy revealed that the oxidation state of the PANI component of the blend at undamaged films, depends on the metal surface used as substrate. Results indicate that the degree of redox conversion of polyaniline, from emeraldine to leucoemeraldine state, strongly depends on the reducing power of metals showing a galvanic coupling between the substrate and polyaniline. On the other way, results reveal that PANI acts as an anion reservoir, which can release anions in a smart way when damage is produced on the surface of the coating forming a second physical barrier to avoid penetration of aggressive ions. This phenomenon was observed for all metal studied in this work.     

甲基丙烯酸甲酯-苯乙烯悬浮聚合共聚物粒度的控制

以过氧化二苯甲酰为引发剂,以聚乙烯醇-羟基磷酸钙复合分散体系为分散剂,采用悬浮聚合法制备甲基丙烯酸甲酯-苯乙烯共聚物珠粒.研究了单体配比、引发剂用量、分散剂用量、反应温度、搅拌速度对聚合物珠粒的影响;并用红外光谱对产物结构进行了表征.     

Thermal treatment and dynamic mechanical thermal properties of polyaniline

Thermal transitions of polyaniline in the emeraldine base form (Pani-EB) were studied by DMTA using two series of thermally treated samples. In the first series the specimens were annealed at 70 °C for 5, 15 min, 1 and 3.5 h. In the second they were submitted to annealing at 100 °C during the same periods of time plus a 24 h treatment. Two transitions were observed at sub-zero temperatures and were attributed to the motion of solvated water and solvent (NMP). The glass transition and the highest temperature relaxation, assigned to crosslinking depended on the degree of solvation resulting from the thermal treatment. A linear contraction of Pani-EB films with residual water evaporation was reported for the first time.     

Morphology and conductivity of polyaniline nanofibers prepared by ‘seeding’ polymerization

Conventional polymerized polyaniline (PANI) dissolved in dimethyl sulphoxide (DMSO) was used as ‘seed’ to induce the polymerization of aniline and hence prepare PANI nanofibers. The different preparation conditions including acid concentration, reaction time, aniline concentration, PANI/DMSO amount, PANI/DMSO concentration, acid and organic solvent kinds were investigated to discuss the influence of these conditions on the morphology and conductivity of the resulting samples. FT-IR spectra were measured to give further proof for the different effect on the conductivity. The scanning electro microscope images of PANI product extracted from the reaction solution at different time were collected and a comparison between this ‘seeding’ polymerization, conventional and rapidly mixing polymerization was also made to make clear the advantage of this approach and the mechanism of the formation of PANI nanofibers.     

Optically active fluoro-substituted polyaniline prepared in organic media: The synthesis, chiroptical properties, and comparison with optically active non-substituted polyaniline

Optically active polyaniline (PANI) bearing an electron-withdrawing fluorine substituent, poly(2-fluoroaniline) (F-PANI), was synthesized in organic solvents by using (+)- or (−)-camphorsulfonic acid (CSA) as a chiral dopant, in which 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) was used as an electron acceptor. Formations of the optically active (chiral) F-PANI/(+)- or (−)-CSA, the dedoped F-PANI, and the redoped F-PANI/CSA were confirmed by the FT-IR, UV/vis/near-IR, and/or circular dichroism (CD) spectroscopy. The CD spectra of the chiral F-PANIs/(+)- and (−)-CSA were investigated in various organic solvents and compared with those of non-substituted PANI/(+)- or (−)-CSA. The F-PANI/(+)-CSA and PANI/(+)-CSA interestingly indicated almost mirror-imaged CD spectra in the visible region, although CD absorptions of the F-PANI/CSA were slightly blue shifted compared with those of PANI/CSA. The chiral F-PANI/CSA was unexpectedly confirmed to remain the initial chiral conformation during reversible dedoping/redoping cycles in solution state. The chiroptical properties of F-PANI/(+)-CSA in organic solvents were found to be affected by the solvent, probably due to the solvent effect to the polymer backbone, and the helical conformation was drastically reversed by change of the solvent. Furthermore, the conformation of F-PANI/CSA in m-cresol can be significantly changed when the F-PANI/CSA was dissolved in cosolvent of m-cresol and DMSO at various volume ratios, in which the sign inversions of CD absorption bands were caused when the ratio of DMSO in the m-cresol/DMSO cosolvent exceeded 10%. On the other hand, in the case with PANI/(+)-CSA, the similar sign inversions of CD absorption bands were not observed under the similar conditions, and then the helical conformation of chiral F-PANI/CSA was supposed to be rather flexible compared with that of chiral PANI/CSA, presumably due to relatively weak interaction among F-PANI backbone, CSA, and m-cresol.     

Dynamic and static properties of SBS triblock copolymer and their blends

By using a dynamic testing method (Rheovibron), it has been established that for a pure triblock copolymer (styrene-butadiene-styrene, SBS), the morphology is composed of a continuous phase, a dispersed phase and an interphase. The predominance of the phase depends upon whether the polymer is cast from a good or poor solvent for each block. For the blends of SBS with PS and PBd, the interphase occupies a greater fraction as indicated by the fact that its corresponding molecular relaxation temperature range is much broader (10°–80°C) than that of pure SBS (60°–80°C). If the blends of SBS with its corresponding homopolymers are heated at 140°C for 45 min, the fraction of the interphase increases significantly and the onset of molecular relaxation is lowered to ?10°C. The viscosities of SBS and their blends are measured by both dynamic and static methods. Complex viscosities calculated from the dynamic method show transitions similar to those of storage moduli. Viscosities at different temperatures from these two methods are superimposed onto master curves.     

Effect of secondary dopants on electrochemical and spectroelectrochemical properties of polyaniline

Polyaniline (PANI) was doped with poly(styrene sulfonic acid) (PSS) via doping-dedoping-redoping procedure. Incorporation of PSS in PANI resulted modifications in electrochemical and electrochromic properties, morphology and polymer structure of the polymer film as evidenced by the results of cyclic voltammetry, in situ UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis and conductivity measurements. PANI doped with PSS was found to have a cross-link/branched structure with a minimum degradation product. The absence of degradation products improves the electrochemical, electrochromic properties and thermal stability of the PANI layer for electrochromic applications.