Thermal dynamic processing of polyaniline with dodecylbenzene sulfonic acid (original) (raw)
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Synthetic Metals, 1999
. Synthesis of polyaniline PANI was performed under different conditions followed by dedoping, redoping with dodecyl benzene Ž . sulfonic acid DBSA and then blending with PS. The morphologies of the as-polymerized, doped and blended PANI were studied. The Ž . main polymerization stages seem to include: PANI oligomers assembling into nuclei, nuclei growing into primary particles 10 nm , Ž . Ž . primary particles assembling into aggregates f 0.5 mm and aggregates assembling into agglomerates f 10 mm . The morphology of the as-polymerized PANI was found to be strongly related to the rate of oxidant addition, synthesis duration and synthesis temperature. This morphology dominates the effects of DBSA doping and dispersing the resulting PANI-DBSA in the matrix polymer. A fine PANI-DBSA powder with weakly bound aggregates is likely to disperse well in a solvent and hence promote the formation of the desired fine-network morphology and yield a low percolation threshold and high conductivity. Synthesis at a high oxidant addition rate, an excess of oxidant, a relatively high polymerization temperature and a short synthesis duration should diminish the tendency to form dense complex structures. These dense structures prevent efficient DBSA doping, deaggregation and the desired fine-network dispersion of PANI-DBSA in the blends. q 1999 Elsevier Science S.A. All rights reserved.
Conductive polyaniline–SBS blends prepared in solution
Synthetic Metals, 2001
Conducting rubbery blends of styrene-butadiene-styrene (SBS) triblock copolymer and polyaniline doped with dodecylbenzenesulfonic acid (DBSA) were produced from solution. The Pani.DBSA used in these studies was prepared by the``in situ doping polymerization'' which gives rise to material with electrical conductivity as high as 4 S/cm and a protonation degree of 65%, as indicated by X-ray photoelectron spectroscopy (XPS). The¯exible and transparent, free-standing ®lms obtained by casting displayed low percolation threshold. Conductivity level close to the pure Pani.DBSA was also achieved by using around 20 wt.% of Pani.DBSA in the blends. Solution blends prepared by magnetic stirring display higher conductivity than those obtained by sonication. The last method leads to a very dispersed conducting particles, as observed by optical microscopy, which contribute for a lower conductivity values. The formation of microtubules was observed by scanning electron microscopy in both Pani.DBSA and their blends with SBS. #
Polyaniline–DBSA/polymer blends prepared via aqueous dispersions
Synthetic Metals, 2000
. Stable polyaniline-dodecyl benzene sulfonic acid PANI-DBSA aqueous dispersions were obtained by a unique method of aniline polymerization in the presence of DBSA, through an anilinium-DBSA complex appearing as solid needle-like particles, in an aqueous Ž . medium. The average size of the PANI primary particles, determined by small angle X-ray scattering SAXS , is 18.7 nm. These primary particles form aggregates, which further cluster into ; 50 mm agglomerates. PANI-DBSArpolymer blends were obtained by mixing an aqueous PANI-DBSA dispersion with an aqueous emulsion of the matrix polymer, followed by water evaporation. These blends exhibit Ž . electrical conductivity already at a very low PANI-DBSA content 0.5 wt.% . The conductivity level of the various blends depends on the PANI content, on the surfactant present in the polymer matrix emulsion, and it is practically independent of the polymer matrix Ž nature. Thus, a similar structuring mechanism prevails in these blends, irrespective of the polymer matrix contrary to solution and melt . blends . The PANI-DBSA particles strongly segregate within the polymer matrix, already in the combined aqueous dispersion, and upon drying, a very fine conductive network is formed. This strong segregation tendency leads to a conductive network formation already at low PANI-DBSA contents, thus generating the conductive blends. q
Electrically conductive, melt-processed polyaniline/EVA blends
Journal of Applied Polymer Science, 2001
Mechanical blends of ethylene–vinyl acetate copolymer and polyaniline doped with dodecyl benzene sulfonic acid (PAni–DBSA) were prepared in a two-roll mill at 50°C and in a Haake internal mixer at 150°C. The effects of the blend composition and processing conditions on the electrical conductivity and mechanical properties were investigated. These blends exhibited high levels of electrical conductivity at a small amount of PAni complex. Blends prepared in a two-roll mill displayed conductivity values as high as 1 S/cm and a higher protonation degree than the pure PAni–DBSA, as indicated by X-ray photoelectron spectroscopy. Two different insulator–conductor transition points were observed in these blends. The mechanical performance decreased as the amount of PAni–DBSA increased, indicating blend incompatibility and a plasticizing effect of the DBSA. The morphology of the blends were studied by scanning electron microscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 114–123, 2001
Studies on SLS doped polyaniline and its blend with PC
Journal of Applied Polymer Science, 2001
Electrically conductive polyaniline (PANI) and its blend with polycarbonate (PC) was prepared by one-step emulsion polymerization technique in which sodium lauryl sulfate (SLS) acts as surfactant and as a protonating agent for the resulting polymer. The prepared PANI and its blends were characterized by density, percentage of water absorption, and electrical conductivity. PANI–PC blend exhibits a conductivity value of 4.70 × 10−2 S/cm (PANI–PC1) and 5.68 × 10−5 S/cm (PANI–PC3) with a change in dopant from p-toluene sulfonic acid (TSA) to SLS, respectively. By using a more general method, which takes into account the presence of disorder of the second kind in polymers proposed by Hosemann, crystal size (〈N〉) and lattice strain (g in %) values were estimated. The variation of conductivity in doped PANI and PANI–PC blend has been explained on the basis of these microcrystalline parameters. TGA thermograms of PANI and PANI-PC blend show three-step degradation behavior. Thermal stability of PANI was improved after blending with PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 383–388, 2001
Conductivity and structure of melt-processed polyaniline binary and ternary blends
Polymers for Advanced Technologies, 2000
In the present study, conductive binary and ternary blends containing polyaniline (PANI) were developed through melt blending. The binary blends' investigation focused on the morphology, in light of the components' interaction, and the resulting electrical conductivity. Similar solubility parameters of a given doped PANI and a matrix polymer lead to dispersion of fine PANI particles within the matrix, and to formation of conducting paths at low PANI contents. A plasticizer acting also as a compatibilizer improves the matrix polymer/PANI interactions. In ternary blends consisting of PANI and two immiscible polymers, the PANI preferrentially locates in one of the components, affecting the blend's morphology. This ªconcentratingº effect leads to relatively high electrical conductivity at a low PANI content. The electrical conductivity of the studied ternary blends is almost independent of the components' sequence of addition into the hot melt mixing device, exhibiting the selectivity of PANI towards one of the components.
Polymer, 2006
Electrically conductive blends based on polyanilineedodecylbenzene sulfonic acid (Pani.DBSA)/styreneebutadieneestyrene (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 ultravioletevisible (UVevis) 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.
Macromolecules, 2000
New solution processing systems were studied with the goal to obtain highly conductive polyaniline films with good mechanical properties and its conducting blends with poly(methyl methacrylate). A new dopant, namely, 1,2-benzenedicarboxylic acid, 4-sulfo, 1,2-di(2-ethylhexyl) ester (DEHEPSA), was studied as a protonating agent. It was found that the use of this dopant together with dichloroacetic acid (DCAA) or difluorochloroacetic acid (DFCAA) as solvents leads to films showing conductivities of 180 and 100 S/cm, respectively. Films cast from DCAA are metallic in character down to 220 K. Since the protonation agent used exhibits doping as well as plasticizing properties, the resulting polyaniline films, in addition to high conductivity, show excellent flexibility and much lower glass-transition temperature, T g, (280 K) as compared to polyaniline doped with other protonating agents. Moreover, the same processing system can be used for the fabrication of polyaniline-poly(methyl methacrylate) blends with low percolation threshold (much below 1 wt % of PANI). Upon casting, the overwhelming majority of the solvent can be efficiently removed from the polymer matrix, whereas the remaining residual solvent is strongly bound to the polymer matrix. For this reason, the resulting blends do not show the disadvantages of the blends cast from m-cresol which release the residual solvent upon aging.
Progress in Polymer Science, 2003
Interest in applications for polyaniline (PANI) has motivated investigators to study its mechanical properties, the thermostability of its conductivity, its processibility, etc. and its use in polymer composites or blends with common polymers. As a result, several methods to produce composites/blends containing PANI have been developed, allowing the preparation of a wide spectrum of such materials. Here, generalized approaches for the preparation of such materials are reviewed. Specifically, we consider two distinct groups of synthetic methods based on aniline polymerization either (1) in the presence of or inside a matrix polymer or (2) the blending of a previously prepared PANI with a matrix polymer. Some aspects of these methods are analyzed, emphasizing features that determine properties of the final composites/blends. q