Improved electrorheological effect in polyaniline nanocomposite suspensions

We prepared polyaniline (PANI)/clay composites that are composed of both PANI-clay nanocomposite particles and pure PANI particles. The PANI-clay nanocomposite particles were made during the polymerization process, wherein PANI particles are attached on the surface of exfoliated clay particles modified by an aminosilane group. The PANI/clay composites were used as electrorheological fluids (ERFs) by dispersing them in silicon oil. The PANI-clay nanocomposite particles, which can form columnar structure under an electric field, strongly enhance the mechanical rigidity of the suspensions. The maximum yield stress of the PANI/clay composite suspensions (15 wt% in silicon oil) was 1.6 kPa at 3 kV/mm, while that of pure PANI was 300 Pa at the same electric field. A mechanism to explain the yield behaviors of the PANI-based nanocomposite suspensions is proposed.     

Synthesis and electrorheological characterization of emulsion polymerized SAN‐clay nanocomposite suspensions

Styrene‐acrylonitrile (SAN) copolymer‐clay nanocomposite was synthesized by emulsion polymerization, which is the easiest method of intercalation (e.g., melt or solution intercalation). Existence of the intercalated polymer was verified by Fourier transform‐infrared spectroscopy and X‐ray diffraction (XRD) analysis. From XRD, we confirmed the insertion of styrene‐acrylonitrile copolymer between the interlayers of clay, whose separation consequently becomes larger than that of the polymer‐free clay. Thermogravimetric analysis showed that the thermal stability of the organic polymers was sustained. Using electrorheological (ER) fluids composed of intercalated particles and silicone oil, we observed typical ER behavior, such as higher shear stress in the presence of an electric field and increasing yield stress with particle concentration. We further observed the critical shear rate at which the ER fluids exhibit pseudo‐Newtonian behavior.     

Characterization and thermal degradation studies on polyaniline‐intercalated montmorillonite nanocomposites prepared by a solvent‐free mechanochemical route

Polyaniline (PANI)‐montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ polymerization within the nano‐interlamellar spaces under solvent‐free conditions. The basal spacing of aniline‐intercalated MMT increased gradually up to 1.5 nm with increasing amounts of aniline loaded. This result suggests that aniline molecules were adsorbed by MMT clay and that intercalated aniline likely located perpendicular to the silicate sheets. After polymerization, X‐ray diffraction and Fourier transform infrared analyses confirmed the successful synthesis of PANI chains between the MMT nano‐interlayers. The scanning electron microscopy images indicated that the surface morphologies of PANI–MMTs were strongly different depending on the PANI content. The electrical conductivities of PANI nanocomposite particles in pressed pellets ranged in the order of between 10^?3 and 10^?2 S/cm. UV–vis spectroscopy and doping level measurement were further used to discuss the conductivities of nanocomposites. The thermal stabilities of PANI–MMT nanocomposites were examined by using thermogravimetric‐differential thermal analysis and derivative thermogravimetric analysis, and both analyses consequently demonstrated the improved thermal stabilities of the PANI chains in the nanocomposites as compared to pure PANI. The thermal stabilities of resulting nanocomposites were strongly related to the PANI content, which increased as the PANI content decreased in the nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2705–2714, 2005     

Polyaniline and its modification for electroresponsive material under applied electric fields

Polyaniline (PANI) and its various copolymers were synthesized using different monomers such as o‐methyl‐, o‐methoxy‐, o‐ethyl‐, o‐ethoxyaniline and sodium diphenylamine sulfonate by the chemical oxidation polymerization as air‐stable organic conducting polymers, and adopted as one of the most potential materials of electrorheological (ER) fluids, especially for the anhydrous system. A relatively low density, a controllable conductivity, and thermal stability are advantages of the PANI based ER system compared with other ER materials. An FT‐IR analysis was adopted to confirm their synthesis and a scanning electron microscopy (SEM) analysis indicated the shape of PANI derivatives was irregular. The effect of functional group of PANI on electric and electroresponsive properties of poly(aniline‐co‐ethoxyaniline) (COPA) particles were examined. A universal scaling equation of the yield stress was applied to these ER fluids and it was found that all data were collapsed successfully onto a single curve regardless of monomer type of the polyaniline synthesized. Copyright © 2005 John Wiley & Sons, Ltd.     

Studies on the conducting nanocomposite prepared by in situ polymerization of aniline monomers in a neat (aqueous) synthetic mica clay

The in situ polymerization of the anilinium‐intercalated synthetic mica clay can easily result in an intercalated polyaniline (PANI)/clay nanocomposite. The FT‐IR spectra demonstrated a significant shift for ν_{(C? N)} at 1292 cm^?1 of the templated polymerized and intercalated PANI molecules. A red shift of λ_max for PANI was found from UV–vis spectra. The intercalated PANI also expanded the clay basal spacing seen from WAXD patterns. The degradation rate and temperature of the nanocomposites were found to alleviate and increase compared to neat PANI, respectively. The microscopic examinations including TEM, SEM, and AFM pictures of the nanocomposite demonstrated an entirely different and more compatible morphology. Conductivity of nanocomposite gradually increased with PANI and apparent increase was found when intercalated PANI content reached 40.6 wt %, the possible percolation threshold. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1800–1809, 2008     

Poly(styrene‐b‐tetrahydrofuran)/clay nanocomposites by mechanistic transformation

Synthesis of poly(styrene‐block‐tetrahydrofuran) (PSt‐b‐PTHF) block copolymer on the surfaces of intercalated and exfoliated silicate (clay) layers by mechanistic transformation was described. First, the polystyrene/montmorillonite (PSt/MMT) nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. Transmission electron microscopy (TEM) analysis showed the existence of both intercalated and exfoliated structures in the nanocomposite. Then, the PSt‐b‐PTHF/MMT nanocomposite was prepared by mechanistic transformation from ATRP to cationic ring opening polymerization (CROP). The TGA thermogram of the PSt‐b‐PTHF/MMT nanocomposite has two decomposition stages corresponding to PTHF and PSt segments. All nanocomposites exhibit enhanced thermal stabilities compared with the virgin polymer segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2190–2197, 2009     

Synthesis and new application of green and recyclable cyclic poly(L‐lactide)‐clay hybrid

We report on the application of biodegradable cyclic poly(L ‐lactide) (PLLA) as new stabilizer; synthesis and application of a cyclic PLLA‐clay hybrid material as recyclable catalyst support. Cyclic PLLAs were used to stabilize palladium nanoparticles synthesized by a wet chemical method. It was found that the palladium particles were smaller with cyclic PLLA stabilizer (～5–10 nm) than the particles obtained from linear PLLA. The cyclic PLLA‐clay hybrid was prepared by a zwitterionic ring‐opening polymerization catalyzed by in situ‐generated N‐heterocyclic carbene catalyst. Palladium (0) nanoparticles were supported and well dispersed on the cyclic PLLA‐clay hybrid to form a new nanocomposite. The nanocomposite was found to be a highly efficient and recyclable catalyst for the aminocarbonylation reactions of aryl halides with various amines. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4167–4174     

Electrorheological characteristics of polyaniline/titanate composite nanotube suspensions

In this paper, one-dimensional polyaniline/titanate (PANI/TN) composite nanotubes were synthesized by in situ chemical oxidative polymerization directed by block copolymer. These novel nanocomposite particles were used as a dispersed phase in electrorheological (ER) fluids, and the ER properties were investigated under both steady and dynamic shear. It was found that the ER activity of PANI/TN fluids varied with the ratio of aniline to titanate, and the PANI/TN suspensions showed a higher ER effect than that made by sphere-like PANI/TiO₂ nanoparticles. These observations were well interpreted by their dielectric spectra analysis; a larger dielectric loss enhancement and a faster rate of interfacial polarization were responsible for a higher ER activity of nanotubular PANI/TN-based fluids.     

Polyaniline‐Stabilized Intertwined Network‐like Ferrocene/Graphene Nanoarchitecture for Supercapacitor Application

The present work highlights the effective H–π interaction between metallocenes (ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline (PANI) through π–π interactions. The PANI‐stabilized Fc@graphene nanocomposite (FcGA) resembled an intertwined network‐like morphology with high surface area and porosity, which could make it a potential candidate for energy‐storage applications. The relative interactions between the components were assessed through theoretical (DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI‐stabilized ternary nanocomposite exhibited a maximum specific capacitance of 960 F g⁻ at an energy density of 85 Wh Kg⁻¹ and a current density of 1 A g⁻. Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as‐prepared nanocomposites, which showed improved charge‐transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86 %, thus demonstrating the good reversibility and durability of the electrode material.     

Enhanced electrorheology of conducting polyaniline confined in MCM-41 channels

A composite material of a silica-based mesoporous molecular sieve, MCM-41, with conducting polyaniline (PANI) inside the uniformly aligned one-dimensional channels (PANI/MCM-41) was prepared and its nanocomposite formation was confirmed through an electrical conductivity measurement. This nanocomposite particle was adopted for a dispersed phase in electrorheological (ER) fluids, and the ER property was measured using a Couette-type rotational rheometer equipped with a high voltage generator. Suspension of PANI/MCM-41 showed ER properties more enhanced than those of MCM-41 or PANI alone as a result of the anisotropic polarization of the PANI/MCM-41 nanocomposite.     

Controllable synthesis of novel sandwiched polyaniline/ZnO/polyaniline free‐standing nanocomposite films

Controllable synthesis of novel sandwiched polyaniline (PANI)/ZnO/PANI free‐standing nanocomposite films is reported via spin coating of ZnO quantum‐dot interlayer on PANI base layer and then PANI surface layer on the ZnO interlayer. The thickness of the ZnO interlayer and the PANI surface layer can be easily controlled by adjusting spin time and spin speed, respectively. The effects of the ZnO interlayer thickness and the PANI surface layer thickness are examined in detail on the photoluminescence (PL) property. It is worth noting that coverage of the PANI surface layer on the ZnO interlayer can not only lead to great enhancement in the PL property but also to a maximum PL intensity at a medium PANI surface layer thickness. This maximum PL property is caused by the combined ZnO/PANI carrier transportation and PANI shielding effects. In addition, the nanocomposite films show reasonably good conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Co‐continuous Polyamide 6 (PA6)/Acrylonitrile‐Butadiene‐Styrene (ABS) Nanocomposites

Summary: Polyamide 6 (PA6)/acrylonitrile‐butadiene‐styrene (ABS) (40/60 w/w) nanocomposites with a novel morphology were prepared by the melt mixing of PA6, ABS and organoclay. The blend nanocomposites had a co‐continuous structure, in which both PA6 and styrene‐acrylonitrile (SAN) were continuous phases. It was found that the toughening rubber particles were only located in the SAN phase and the strengthening clay platelets were selectively dispersed in the PA6 phase. The co‐continuous nanocomposites showed greatly improved mechanical properties over the whole temperature range when compared with the same blend sample without clay.

Schematic diagram for the co‐continuous ABS/PA6 blend nanocomposite.     

Polyurethane/polyaniline and polyurethane‐poly(methyl methacrylate)/polyaniline conductive core‐shell particles: Preparation,morphology, and conductivity

Polyurethane/polyaniline (PU/PANI) and polyurethane‐poly(methyl methacrylate)/polyaniline (PU‐PMMA/PANI) conductive core‐shell particles were synthesized by a two‐stage polymerization process. The first stage was to produce a core of PU or PU‐PMMA via miniemulsion polymerization using sodium dodecyl sulfate (SDS) as the surfactant. The second stage was to synthesize the shell of polyaniline over the surface of core particles. Hydrogen chloride (HCl) and dodecyl benzenesulfonic acid (DBSA) were used as the dopant agents. Ammonium persulfate (APS) was used as the oxidant for the polymerization of ANI. Different concentrations of HCl, DBSA, and SDS would cause different conformations of PANI chains and thus different morphologies of PANI particles. UV–visible spectra revealed that the polaron band was blue‐shifted because of the more coiled conformation of PANI chains by increasing the concentration of DBSA. Besides, with a high concentration of DBSA, both spherical‐ and rod‐shape PANI particles were observed by transmission electron microscope, and the coverage of PANI particles onto the core surfaces was improved. The key point of formation of rod‐type PANI particles was that DBSA was served with a high concentration accompanied with the existence of HCl or SDS. The better coverage of PANI particles over the core surfaces by charging higher DBSA concentrations resulted in a higher conductivity of hybrid particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3902–3911, 2007     

Waterborne trifunctionalsilane‐terminated polyurethane nanocomposite with silane‐modified clay

Trifunctional organosilane‐modified clay was synthesized and used to prepare waterborne trifunctionalsilane‐terminated polyurethane (WSPU)/clay nanocomposite dispersions in this study. Qualitative evidence of the presence of chemically attached silane molecules on clay were confirmed by Fourier transform infrared spectroscopy. The grafted amount and the grafting yield were determined by thermogravimetric analysis and the obtained results were in good agreement with the cation exchange capacity of pristine clay. X‐ray diffraction and transmission electron microscopy examinations indicated that the clay platelets are mostly intercalated or partially exfoliated in the SPU matrix with a d‐spacing of ～2.50 nm. Clay does not influence the location and peak broadness of the glass transition temperature of soft segment as well as hard segment domains in the WSPU/clay films. WSPU/clay dispersion with higher clay content exhibits a marginal increase in the average particle size, but silane modified clay has a pronounced effect compared with Cloisite 20A‐based nanocomposites. In addition, the incorporation of organophilic clay can also enhance the thermal resistance and tensile properties of WSPUs dramatically through the reinforcing effect. The improvement in water and xylene resistance of the silane modified clay nanocomposites proved that trifunctional organosilane can be used as effective modifiers for clays. Storage stability results confirmed that the prepared nanocomposite dispersions were stable. This method provides an efficient way to incorporate silane modified clay in SPU matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2747–2761, 2007     

Self‐assembly in a polystyrene/montmorillonite nanocomposite

A self‐assembly phenomenon in an extruded polystyrene/clay nanocomposite sample is observed during a temperature increase process. Wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), and infrared dichroism techniques have been employed to investigate the self‐assembly phenomenon. The results show that in the self‐assembly structure the montmorillonite primary particles orient parallel, and the phenyl rings of the polystyrene align perpendicular to the primary particles, whereas no obvious orientation of the aliphatic chain was observed.     

Synthesis and electrorheological behavior of sterically stabilized polypyrrole-silica-methylcellulose nanocomposite suspension

Various polypyrrole (PPy)-silica-methylcellulose nanocomposite particles were synthesized by suspension polymerization in the presence of silica nanoparticles controlling the ratio of pyrrole, silica, and methylcellulose during the polymerization. The electrorheological (ER) and dielectric properties of the sterically stabilized PPy-silica-methylcellulose nanocomposite suspensions were investigated. The ER response increases with the increase in the silica/pyrrole ratio. The ER behavior also depends on the methylcellulose amount during the polymerization. The yield stress initially increases with the methylcellulose amount, passes through a maximum, and then decreases with the methylcellulose amount. The dielectric constants and dc conductivities of the PPy-silica-methylcellulose nanocomposite particles and the dielectric properties of their suspensions indicate that the increased ER response arises from the enhanced interfacial and particle polarization which depends on the silica/pyrrole ratio and the methylcellulose amount during the polymerization.     

Cold‐drawn induced microstructure in PVC‐bentonite nanocomposites

The mechanical properties and cold drawn‐induced micro and nanostructure of polyvinyl chloride (PVC)‐bentonite nanocomposites have been investigated. Molded sheets with 5 wt% concentration of bentonite and two processing additives were melt extruded and two‐roll‐milled processed. The flame retardant additive promoted polymer intercalation whereas a pigment dispersant promoted clay exfoliation, the polymer matrix showed isotropic orientation. The intercalated nanocomposite exhibited nanoplates oriented with their planes parallel to the molded sheet surface and the Young's modulus and yield stress were significantly enhanced relative to neat PVC. The strain at fracture (～144%) was slightly reduced relative to the matrix (～167%). Cold drawing induced molecular chain orientation along the tensile axis and preserved the orientation of the intercalated nanoclays. The fracture mechanism, as investigated via scanning electron microscopy (SEM) revealed plastic fracture mechanism (similar to neat PVC). On the other hand, the exfoliated nanocomposite did not show any improvement in mechanical properties but rather a significant decay of strain at fracture (～44%). The fractured region, as examined by SEM, exhibited microvoid morphology. Analysis of the fractured region showed PVC macromolecules oriented along the tensile axis but no preferred orientation of the nanoclays. The limited strain at fracture found for this material appears to be associated with the initially randomly oriented nanoclays being unable to orient under the tensile deformation. The nanoclays would act as stress concentrators leading to rapid material's failure due to loss of adhesion with the polymer matrix. The results suggest that exfoliated nanoclays could play a detrimental role when the nanocomposite is subjected to large deformations at temperatures well within the glassy regime. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and electrorheological properties of polyaniline-Na+-montmorillonite suspensions

We synthesized polyaniline-Na⁺-montmorillonite nanocomposite particles using an emulsion intercalation method and prepared electrorheological (ER) fluids by dispersing the synthesized nanocomposite particles in an electrically insulating silicone oil. The conducting polymer (polyaniline) was inserted into the layers of clay, and this insertion of polyaniline was confirmed by X-ray diffraction. For the first time, ER properties were determined via a rotational rheometer equipped with a high voltage generator.     

One‐Step Electrodeposition to Layer‐by‐Layer Graphene–Conducting‐Polymer Hybrid Films

One‐step fabrication of graphene–polyaniline (graphene–PANI) hybrid film was facilely achieved by cyclic voltammetric electrolysis of a bath containing both graphene oxide (GO) and aniline, where graphene is obtained by electrochemical reduction of GO and PANI is simultaneously obtained by aniline electropolymerization. As there is no strong attraction between aniline and GO under the electrodeposition conditions, the independent depositions of PANI and reduced GO nanosheets at their greatly differed potentials led to alternate layered graphene–PANI films, with the topmost layer being PANI particles or graphene sheets just by changing the initial scan directions. The two kinds of graphene–PANI hybrid films present excellent but different electrical and electrochemical behaviors.     

Morphological mapping and analysis of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] and its clay nanocomposites by atomic force microscopy

Atomic force microscopy was successfully applied for comprehensive nanoscale surface and bulk morphological characterization of thermoplastic elastomeric triblock copolymers: poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) having different block lengths and their clay based nanocomposites. Commercially available Cloisite®20A and octadecyl (C₁₈) ammonium ion modified montmorillonite clay (OC) prepared in our laboratory by cation exchange reaction were used. The phase detected images in the tapping mode atomic force microscopy exhibited a well‐ordered phase separated morphology consisting of bright nanophasic domains corresponding to hard component and darker domains corresponding to softer rubbery ethylene‐co‐butylene (PEB) lamella for all the neat triblock copolymers. This lamellar morphology gave a domain width of 19–23 nm for styrenic nanophase and 12–15 nm for ethylene‐co‐butylene phase of SEBS having end to mid block length ratio of 30:70 and block molecular weights of 8800–41,200–8800. On increasing the ratio of block lengths of the polymer matrix and the selectivity of the solvent toward the blocks used for casting, the morphological features of the resultant films altered along with change in domain thickness. The phase images showed position and distribution of the brightest clay stacks in the dark‐bright contrast of the base matrix of the nanocomposite. Exfoliated and intercalated‐exfoliated morphology obtained in the case of Cloisite®20A and OC‐based SEBS nanocomposites, respectively, is further supported by X‐ ray diffraction and transmission electron microscopy studies. The lamellar thickness of the soft phases widened to 50–75 nm, where the layered clay silicates (40–54 nm in length and 4–17 nm in width) were embedded in the soft rubbery phases in the block copolymeric matrix of the nanocomposite. The marginally thicker width of the hard styrenic phases and slightly shrinked width of the soft rubbery lamella can be observed from the regions where no nanofiller is present. Distinct differences in bulk morphologies of the nanocomposites prepared in the melt and the solution processes were obtained with nanocomposites. The presence of clay particles was evident from the almost zero pull‐off and snap‐in force in the force‐distance analysis of SEBS based nanocomposite. This analysis also revealed stronger tip interaction resulting in highest contact and adhesive forces with the softer PEB region relative to the harder PS region. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 52–66, 2007