Studies on one‐dimensional polyanilines prepared with n‐dodecylbenzenesulfonic and camphorsulfonic acids

Anilinium salts complexed with n‐dodecylbenzenesulfonic acid (DBSA) and camphorsulfonic acid (CSA) were found to self‐assemble into cylindrical micelles with bigger diameters than those complexed with only DBSA or CSA. These cylindrical micelles were polymerized into one‐dimensional copolyaniline nanotubes (PANIDBSACSA) via emulsion polymerization, demonstrating various morphologies depending on the ratio of DBSA to CSA. The UV?visible?NIR spectra of neat PANICSA and PANIDBSACSAs illustrate significant free carrier tails in the NIR region and conductivity 10–20 times higher than that of neat PANIDBSA whose UV?visible?NIR spectrum does not illustrate significant carrier tails. When the number of moles of DBSA is equivalent to or exceeds that of CSA in the polymerization mixture, SEM and TEM micrographs of the PANIDBSACSAs reveal that they have larger diameters than that of neat PANIDBSA. Besides, some of the surfaces of the big nanotubes were implanted and mounted with lots of small nanofibers of neat PANICSA polymerized from some of the CSA‐complexed aniliniums which were excluded from the cylindrical micelles before polymerization. TGA thermograms of PANIDBSACSAs show an intimate relationship between thermal deprotonation and the DBSA to CSA ratio. X‐ray diffraction patterns demonstrate a layered structure arrangement of polyaniline molecules of all one‐dimensional nanofibers. © 2015 Society of Chemical Industry     

Synthesis and characterization of organo‐attapulgite/polyaniline‐dodecylbenzenesulfonic acid based on emulsion polymerization method

Organo‐attapulgite (OAT) was obtained by pretreating attapulgite (AT) with hexadecyltrimethyl ammonium bromide (HDTMABr) and dodecylbenzenesulfonic acid doped polyaniline (PAn‐DBSA) (OAT/PAn‐DBSA) was synthesized by emulsion polymerization at different OAT weight ratios. The perhaps polymerization procedure was supposed. The chemical structure and electronic absorption of the composites was confirmed by FTIR and UV–Vis spectroscopy, respectively. According to the X‐ray diffraction (XRD) results, it can be concluded that HDTMABr and PAn‐DBSA was just adsorbed on the surface of AT during the cation‐exchange process and OAT respectively without destroying the crystalline structure of AT or OAT. The composites showed a higher thermal stability than pure PAn‐DBSA by introduction of OAT into this polymerization system by using TGA analysis. Morphologies of the samples were confirmed by TEM and it showed that OAT was dispersed well in organic solvent after AT was pretreated with HDTMABr. The morphologies of OAT/PAn‐DBSA also supported the perhaps formation procedure we hypothesized. The electrical conductivity of the composite decreased with increasing the feed weight ratios of OAT in this polymerization system. POLYM. COMPOS., 2008 © 2007 Society of Plastics Engineers     

Exploration of the morphological transition phenomenon of polyaniline from microspheres to nanotubes in acid‐free aqueous 1‐propanol solution in a single polymerization process

Polyaniline micro‐ or nanostructures have been widely investigated due to their unique physical and chemical properties. Although several studies have reported the synthesis of polyaniline microspheres and nanotubes, their mechanisms of formation remain controversial. This study reports our observation of the morphological transition of polyaniline from microspheres to nanotubes in a single polymerization process and also tries to propose their mechanisms of formation. The polymerization of aniline monomer in acid‐free aqueous 1‐propanol solutions (1 and 2 mol L^?1) produces polyaniline microspheres and nanotubes at different reaction stages through a morphology transition process with treatment using ultrasound. In the initial reaction stage, Fourier transform infrared spectra indicate that the aniline monomers form phenazine‐like units, producing polyaniline microspheres with an outside diameter of 1–2 µm. The hydrogen bonds between 1‐propanol and polyaniline serve as the driving force for the polyaniline chains to build microspheres. As the reaction continues, observation indicates the microspheres decompose and reform one‐dimensional nanotubes. In this stage, a structure consisting of a head of phenazine‐like units and a tail of acid‐doping para‐linked aniline units develops. The protonation of the para‐linked aniline units provides the driving force for the formation of nanotubes through a self‐curling process. We report here the unique morphology transition of polyaniline from microspheres to nanotubes in a single polymerization process. The results indicate that the structural change of polyaniline leads to this morphological change. The mechanisms of formation of the microspheres and nanotubes in a polymerization process are also well explained. Copyright © 2010 Society of Chemical Industry     

Branched and curved nanotubular polyaniline synthesized by emulsion polymerization in presence of zinc salts of n-dodecylbenzenesulfonic acid

The presence of zinc salts of DBSA (n-dodecylbenzenesulfonic acid), designated as Zn(DBSA)₂, induced some branches and curvature of the resultant polyaniline nanotubes. These branched or curved nanotubes can be clearly seen from their SEM and TEM micrographs taken for various polyaniline nanotubes prepared in the presence of Zn(DBSA)₂. For branched or curved polyaniline nanotubes, the conjugation chain length can be monitored by the position of their λ_maxs in the UV-Vis-NIR spectra.     

The structure and electro‐mechanical properties of novel hybrid CNT/PANI nanocomposites

Electrically conductive elastomeric nanocomposites containing carbon nanotubes (CNT) and polyaniline (PANI) are reported in the present investigation. The synthesis procedure included an in situ inverse emulsion polymerization of aniline doped with dodecylbenzene sulfonic acid (DBSA) in the presence of CNT and dissolved styrene‐isoprene‐styrene (SIS) block copolymer. The PANI synthesis step was carried out by applying ultrasonic energy. The dispersions obtained were processed by two methods: a recently developed precipitation‐filtration procedure, and a conventional drop‐cast procedure. The techniques developed resulted in homogeneous exfoliated PANI coated nanotubes within the elastomeric matrix. The presence of CNT/PANI in the SIS elastomeric matrix affects thermal, mechanical, and electrical properties of the nanocomposites. The formation of continuous three‐dimensional CNT/PANI networks prepared via the precipitation‐filtration method enhances the nanocomposite properties. Contrarily, the intermittent three‐dimensional network prepared by conventional drop‐cast method leads to inferior properties. Nanocomposites produced by both techniques are observed by HRSEM. The two processing techniques result in different structures, which affect the physical properties of the materials produced. A relatively low percolation threshold for both methods was determined. The Young's modulus of the SIS/CNT/PANI significantly increased in the presence of CNT. The precipitation‐filtration technique yields an improved nanocomposite product compared to the drop‐cast route. POLYM. COMPOS., 35:788–794, 2014. © 2013 Society of Plastics Engineers     

Formation mechanism of a nanotubular polyanilines prepared by an emulsion polymerization without organic solvent

A nanotubular polyaniline (PANINT) was prepared from a simple emulsified polymerization method without oil solvent present. A mechanism of the formation of the nano-fibers/tubes was proposed to show that it started with the connecting arrangement of the neighboring anilinium micelles before and during polymerization, which resulted in the formation of the intermediate morphology of centipedes converting into rod-like nanofibers later. The obtained PANINTs displayed not only nanofibrous structure but owned an unusual dispersing behavior in toluene. SEM and TEM showed the dendrite-like networks of nanofibers connected and glued together by the free (not complexed to polyaniline backbone) n-dodecylbenzene sulfonic acid (DBSA) molecules. After removing the free DBSA by acetone, the clear/well-defined empty nanotubes can be seen from TEM in the magnified micrograph. The Atomic force microscopic (AFM) microgaphs demonstrated the cottage like surface morphology of the un-perturbed PANINTs and the morphology was converted to an anisotropic/oriented rods after rubbing on the wet/cast PANINTs' dispersion of toluene before entire evaporation.     

Shielding and dielectric properties of sulfonic acid‐doped π‐conjugated polymer in 8.2–12.4 GHz frequency range

This article deals with dielectric and electromagnetic interference shielding properties of the polyaniline doped with dodecyl benzene sulfonic acid (DBSA) synthesized by microemulsion polymerization of aniline in aqueous solution of DBSA. Dielectric constant and shielding effectiveness due to absorption (SE_A) were calculated using S‐parameter obtained from the vector network analyzer in 8.2–12.4 GHz frequency range. Maximum SE_A of 26 dB (>99%) was achieved for polymer sample. The real part ε′ of complex permittivity shows small variation, whereas the imaginary part ε″ is found to decrease with the increase in frequency. Different formulations have been performed to see the effect of monomer to dopant ratio on intrinsic properties of polyaniline. Further characterization of polymer was carried out by UV–visible and thermal gravimetric analysis, whereas the conductivity measurements were carried out by the four‐probe method.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A Novel Strategy for the Controlled Synthesis of Silver Halide/Polyaniline Nanocomposites with Different Polyaniline Morphologies

Silver halide/polyaniline nanocomposites with different polyaniline morphologies, i.e., nanotubes and nanofibers, were successfully synthesized simply based on the general chemical oxidation polymerization process of aniline in halide acid aqueous solution (i.e., HCl or HBr) with the presence of dodecylbenzenesulfonic acid (DBSA)‐stabilized silver nanoparticles (NPs) as the precursors of silver halide NPs (i.e., AgCl or AgBr). X‐ray diffraction (XRD) and FT‐IR results confirmed the structures of resultant silver halide/polyaniline nanocomposites. TEM and SEM images demonstrated that AgCl or AgBr NPs were well‐dispersed and embedded in the polyaniline matrix. The reasons for the new strategy for the preparation of silver halide/polyaniline nanocomposites were based on two key points: the first was the high reactivity of silver NPs with HCl or HBr to generate AgCl/AgBr NPs. Second, with the assistance of DBSA, polyaniline could be synthesized with various nanostructures, i.e., nanotubes and nanofibers.

     

New amphiphilic sulfonic acid dopant‐cum‐templates for diverse conducting polyaniline nanomaterials

We report new structurally identical polar head amphiphilic sulfonic acids as molecular templates to study the role of the polymerization routes on the solid state properties of polyaniline nanomaterials. Three long chain substituted phenols such as 3‐pentadecylphenol, renewable resource‐cardanol, and nonyl phenol are reacted with sultones to make new long tail amphiphiles. The amphiphilic molecules self‐organized as 4–6 nm tiny micelles in water which were employed as templates for polymerization. Emulsion, dispersion, and interfacial polymerization of aniline along with these new amphiphiles produced well‐defined polyaniline nanofibers, nanotapes, and nanospheres. Electron microscopic analysis revealed that the dopant structure and polymerization routes determine the morphology of the polyaniline nanomaterials. Absorbance studies revealed that the samples produced via interfacial route showed expanded polymer chain conformation as a result of unidirectional growth of the chains in the aqueous‐organic interface. Emulsion and dispersion route samples were produced in coil‐like chain conformation. Powder X‐ray analysis confirmed that the expanded conformation in the polyaniline backbone enhances the high solid state ordering, high percent crystallinity, and larger crystallite size compared to that of the samples with coil‐like conformation. Highly ordered interfacial route samples showed conductivity three orders of magnitude higher than that of the weakly packed polyaniline nanomaterials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of aniline‐formaldehyde resin on the reduced conjugation length of doped polyaniline: Thermal studies

A linear aniline‐formaldehyde resin (AF) complexed with different acids was successfully synthesized with the traditional way of polymerizing a novolac‐type phenolic resin. When the AF(DBSA)_1.0 (AF complexed with only HDBSA (n‐dodecyl benzene sulfonic acid)) was blended with PANI(DBSA)_0.5 (polyaniline doped only by HDBSA, the T_gs (glass transition temperatures) of the polyblends decreased with PANI(DBSA)_0.5, indicating the presence of the compatibility that can alter the doping condition of PANI(DBSA)_0.5 by changing the conjugation length. In the polyblend system, it was also confirmed when the polyblend of 50/50 showed a higher residue weight than the rest of polyblends after being heated up to 450°C. The λ_max of UV–vis spectra of PANI (DBSA)_0.5 demonstrates a red shifts indicating the secondary doping effect (increasing conjugation length) was recovered when PANI(DBSA)_0.5 was mixed with less than 50% of AF(DBSA)_0.5 (HCl)_0.5. Similar phenomenon of red shift was found for the blended samples of PANI(DBSA)_0.5/AF(DBSA)_1.0 at high temperatures. IR spectra revealed an alkyl affinity interaction is present between PANI(DBSA)_0.5 and AF(DBSA)_1.0 at room temperature and a strong and free localized polaron band appeared at high temperatures due to the recovery of secondary doping. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2120–2128, 2007     

Fabrication of DBSA‐doped polyaniline nanorods by interfacial polymerization

An interfacial polymerization was used to fabricate dodecybenzenesulfonic acid (DBSA)‐doped polyaniline (DBSA‐PANI) nanorods with diameter range from 40 nm to 1 μm. The molar ratio of aniline to ammonium peroxydisulfate (APS), the concentrations of DBSA and reaction temperature had an effect on the morphology and size of products. It was found that lower concentration of DBSA and lower temperature will be helpful to the formation of rod‐like PANI nanostructures with a relative small diameter. UV–vis and FTIR measurements were used to characterize the chemical structure of the obtained samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microwave dielectric properties and EMI shielding effectiveness of poly(styrene‐b‐styrene‐ butadiene‐styrene) copolymer filled with PAni.Dodecylbenzenesulfonic acid and carbon black

Conducting composites of polyaniline doped with dodecylbenzenesulfonic acid (PAni.DBSA), carbon black (CB) and poly(styrene‐b‐styrene‐butadiene‐b‐styrene) (STF) as supporting matrix were prepared by in situ polymerization. The influence of components and composition (% w/w) on the electromagnetic properties (dielectric constant ε′ and the dielectric loss ε″) and electromagnetic interference shielding effectiveness (EMI‐SE) of the materials were evaluated with a waveguide, using a microwave network analyzer from 8.2 to 12.4 GHz (X‐band). It was found that CB presence generates adverse effects on PAni.DBSA yield during synthesis, as it can be seen by X‐ray diffraction and TGA analyses. The type of PAni.DBSA formed modifies the composites properties. Dielectric constant, loss factor, and EMI shielding increase with conductive filler loading. Both the fillers, individually and in combination, increase the properties; however, the effect is not additive in nature. POLYM. ENG. SCI., 52:2041–2048, 2012. © 2012 Society of Plastics Engineers     

Melt‐processed polyaniline nanofibers/LDPE/EAA conducting composites

The melt‐processable polyaniline nanofibers doped with superfluous dodecylbenzenesulfonic acid (PANI‐DBSA) were synthesized using the interfacial polymerization and thermal doping technique. Conducting composites composed of PANI‐DBSA nanofibers, low‐density polyethylene (LDPE), and ethylene‐acrylic acid copolymer (EAA) as compatibilizer were prepared by melt processing. The effects of PANI‐DBSA nanofibers on the electrical conductivity, and mechanical properties, and morphological structure of the composites were investigated. As a result, the conducting composites had lower percolation threshold (4 wt%) due to the easy formation of conducting paths for fibrillar‐like PANI‐DBSA in the LDPE matrix, which was also confirmed by the frequency dependence of the real part of the AC conductivity. The Scanning electron microscopy (SEM) images indicated that the PANI‐DBSA nanofibers were dispersed uniformly in the matrix. The mechanical properties of the composites were improved at the low PANI‐DBSA load (about 1 wt%), but they were deteriorated at high PANI‐DBSA content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Polymerization of anilinium/DBSA in the presence of clay particles: Catalysis and encapsulation

This paper describes polymerization of anilinium‐DBSA complex to PANI‐DBSA (DBSA doped polyaniline) in an aqueous dispersion in the presence of mica or talc clays. It is found that the clay presence significantly accelerates the polymerization kinetics by metal ions, such as Fe⁺² ions, present in the clays. Polymerization occurs preferentially on the clay particles' surface, causing their encapsulation with PANI‐DBSA shells. Further coating with PANI‐DBSA takes place on the already coated particles with thin PANI‐DBSA shells by an autoacceleration effect of anilinium‐DBSA polymerization by PANI. It is suggested that the catalytic/autoacceleration effect dominating in the coating process of clay particles with PANI‐DBSA can be extended to other particle/coating systems, which are already under investigation.     

X‐ray photoelectron spectroscopy and electrical conductivity of polyaniline doped with dodecylbenzenesulfonic acid as a function of the synthetic method

X‐ray photoelectron spectroscopy (XPS) has been employed to investigate the protonation degree of polyaniline doped with dodecylbenzenesulfonic acid (Pani. DBSA) obtained by different synthetic methods. The protonation degree has been compared to electrical conductivity. Pani.DBSA prepared through the redoping process in an agate mortar displays conductivity values within the range of 1 S/cm. A protonation level of 48% with almost all imine groups being protonated. Pani.DBSA was also synthesized by oxidative polymerization of aniline in the presence of DBSA, which acts simultaneously as a surfactant and as protonating agent. This in situ doping polymerization was carried out in aqueous or toluene media. In both cases, protonation degrees higher than 50% have been achieved, indicating that a substantial portion of amine units have also been protonated. Higher doping degree has been achieved by aqueous dispersion polymerization of aniline. The C/N and S/N molar ratios obtained by XPS analysis indicate that the polyaniline chains obtained by in situ polymerization are protonated by both sulfonate and hydrogen sulfate anions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 556–565, 2001     

Synthesis and characterization of conducting copolymers from aniline and o‐anisidine in HCl solutions

Conducting poly(aniline‐co‐o‐anisidine) (PAS) films with different ratios of aniline units in the polymer chain were prepared by oxidative polymerization of different molar ratios of aniline and o‐anisidine in 1 M HCl using cyclic voltammetry. Due to the much higher reactivity of o‐anisidine, the structure and properties of PASs were found to be dominated by the o‐anisidine units. The polymerization of poly‐o‐anisidine and PASs followed zero‐order kinetics with respect to formation of the polymer (film thickness) and the autocatalytic polymerization of aniline was completely inhibited. In contrast to polyaniline, a decrease in the polymerization temperature was found to increase the amount of copolymer formed and its redox charge. The presence of aniline units in PASs led to a pronounced increase in the molecular weight and conductivity, and a decrease in the solubility in organic solvents. Repetitive charging/discharging cycles showed that PASs resist degradation more than polyaniline. Copyright © 2003 Society of Chemical Industry     

Viscoelastic characterization of semiconducting dodecylbenzenesulfonic acid doped polyaniline electrorheological suspensions

Dodecylbenzenesulfonic acid (DBSA)‐doped polyaniline particles were synthesized via emulsion polymerization, and electrorheological (ER) fluids were prepared by dispersing the synthesized polyaniline particles in silicone oil. The viscoelastic properties of DBSA‐doped polyaniline/silicone oil ER systems were examined using a vertical oscillation rheometer (VOR), which is designed for the rheological measurement of ER fluids, with a high voltage generator. Viscoelastic data obtained from the VOR were compared with those obtained from a commercial Physica rotational rheometer. The data from VOR were quite reliable in a broad range of both strain and frequency. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 108–114, 2001     

Novel peroxide‐vulcanized NBR‐PAni.DBSA blends,part 1: Preparation and characterization

Blends of poly(butadiene‐co‐acrylonitrile)‐polyaniline dodecylbenzenesulfonate [NBR‐PAni.DBSA] were successfully prepared using an internal mixer for the first time. Electrical conductivities of all the vulcanized blends (up to 10^?2 S/cm with a conductivity percolation threshold 6.0 wt %/5.4 vol % of PAni.DBSA) were not affected with the addition of dicumyl peroxide (DCP) as the vulcanizing agent. The FTIR spectra of vulcanized NBR‐PAni.DBSA blends resembled a superposition of the spectra of the raw materials, but with some notable peak shifts because of the changing intermolecular interactions between the polymers. Blends with ≤30 wt % of PAni.DBSA showed the best compatibility, i.e., with greatest peak shifts for their FTIR spectra and largest temperature shifts for their DSC recorded thermal events. The morphological studies (of both optical and transmission electron micrographs) showed that the thermomechanical mixing method had reduced the amounts of phase separation in all these NBR‐PAni.DBSA blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Solution self‐assembly of tailor‐made macromolecular building blocks prepared by controlled radical polymerization techniques

This review describes the preparation of colloidal aggregates (spherical micelles, cylindrical micelles, polymer vesicles, multicompartment micelles, polyion complexes, schizophrenic micelles) using bottom‐up self‐assembly approaches. In particular, it focuses primarily on the self‐organization of well‐defined macromolecular building blocks (macrosurfactants, polysoaps, polyelectrolytes) synthesized by controlled radical polymerization techniques such as atom transfer radical polymerization, reversible addition fragmentation transfer polymerization and nitroxide‐mediated polymerization. The goal of this review is to highlight that these versatile techniques of polymer synthesis allow the preparation of unprecedented nanostructures in dilute solutions. Copyright © 2006 Society of Chemical Industry     

Poly(1,2‐diaminobenzene) and poly(1,3‐diaminobenzene): Synthesis,characterization, and properties

Poly(1,2‐diaminobenzene) (1,2‐DAB) and poly(1,3‐diaminobenzene) (1,3‐DAB) have been synthesized by using ammonium persulfate as oxidizing agent in the presence and in the absence of the following metal ion salts: CuCl₂, NiCl₂, and CoCl₂ with different HCl concentrations. The products showed a different content of the metal ion depending on the HCl concentration. The polymers were characterized by Fourier transform infrared (FTIR), ultraviolet‐visible (UV‐Vis) spectroscopy, thermal analysis, and electrical conductivity. The polymerization yield depended on the presence of metal ions that can react as oxidizing reagents and/or catalysts. The polymerization mechanism depended on the position of the substituent. For poly(1,2‐DAB) a ladder‐type structure was obtained, and for poly(1,3‐DAB) one similar to that of polyaniline. The thermal stability increased as the metal ion content in the polymer matrix increased. The electrical conductivity of the polymer did not depend on the metal ion content in the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2564–2572, 2002