Interfacial polymerization of morphologically modified polyaniline: from hollow microspheres to nanowires

BACKGROUND: Polyaniline (PANI) has attracted much attention in many fields due to its chemical and physical properties, and different nanostructures of PANI changing from one‐dimensional to three‐dimensional have been obtained. By changing the concentration of cetyltrimethylammonium bromide (CTAB), the morphology of hydrochloric acid‐doped polyaniline could be changed from one‐dimensional nanoneedles or nanowires with a network structure (50–100 nm in diameter) to three‐dimensional hollow microspheres (ca 400 nm in outer diameter) via combining interfacial polymerization and self‐assembly process. RESULTS These different nanostructures of PANI were proved using scanning electron and transmission electron microscopies. A plausible mechanism of the formation of the changeable nanostructures of PANI may be different from that of interfacial polymerization without surfactant or a traditional homogenous reaction system using CTAB as surfactant. CONCLUSION The results obtained from Fourier transform infrared spectrometry, X‐ray diffraction and the four‐probe method showed that the molecular structure of PANI does not change with increasing CTAB concentration, but crystallinity and conductivity of PANI increase with surfactant concentration. Copyright © 2007 Society of Chemical Industry     

Preparation of polyaniline coated polystyrene‐poly(styrene‐co‐sodium 4‐styrenesulfonate) microparticles and the further fabrication of hollow polyaniline microspheres

In this article, the microparticles of polystyrene‐poly(styrene‐co‐sodium 4‐styrenesulfonate) (PS‐PSS) coated by polyaniline (PANI) were prepared and hollow PANI microspheres were further obtained by dissolving the core. First, surface‐sulfonated monodispersed PS was prepared by copolymerization of sodium 4‐styrenesulfonate (SSS) and styrene with dispersion polymerization method. Then aniline was polymerized on the surface of the surface‐sulfonated PS (PS‐PSS) by chemical oxidative polymerization. After purification, we prepared core‐shell (PS‐PSS)/PANI particles. Hollow PANI microspheres were prepared by dissolving the plastic PS core of the (PS‐PSS)/PANI particles in chloroform. The growth process of PANI on the surface of PS‐PSS particles was investigated and the hollow PANI microspheres were characterized. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Surface Tensions of Carbonated 2‐Amino‐2‐methyl‐1‐propanol and Piperazine Aqueous Solutions

Surface tensions of carbonated 2‐amino‐2‐methyl‐1‐propanol (AMP) and piperazine (PZ) aqueous solutions were measured by a surface tension meter which employs the Wilhemy plate principle. A thermodynamic model was proposed to correlate the surface tensions of both CO₂‐unloaded and CO₂‐loaded aqueous solutions by introducing the contribution of CO₂ loading into the formulation of surface tension. Based on experiments and calculations, the effects of temperature, mass fractions of amines, and CO₂ loading on surface tensions of carbonated aqueous solutions were demonstrated.     

Recycling of PET waste using 3‐amino‐1‐propanol by conventional or microwave irradiation and synthesis of bis‐oxazin there from

There is a growing interest in recycling of post‐consumer poly(ethylene terephthalate) (PET) waste for both environmental and economic reasons. PET in the form of disposable soft drink bottle waste was subjected to depolymerization via aminolysis using excess of 3‐amino‐1‐propanol under soxhlet by conventional heating as well as microwave irradiation using catalyst sodium acetate or potassium sulfate. The product obtained was characterized after purification by using melting point, IR spectroscopy, nuclear magnetic resonance, and differential scanning calorimeter and was found to be bis‐(3‐hydroxy propyl) terephthalamide (BHPTA). The BHPTA thus obtained was subjected to cyclization reaction using thionyl chloride to obtain bis‐oxazin under conditions of ambient temperature. Bis‐oxazin has applications in polymer synthesis as a chain extender or a cross linking agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Optical resolution of (R,S)‐2‐phenyl‐1‐propanol through enantioselective ethycellulose membranes

Enantioselective membrane was prepared using ethyl cellulose (EC) as membrane material. The flux and permselective properties of membrane using aqueous solution of (R,S)‐2‐phenyl‐1‐propanol as feed solution was studied. The employed membrane process was a pressure driven process. All kinds of important conditions including preparation and operation of membranes were investigated in this experimentation. When the membrane was prepared with 18 wt % EC, 20 wt % N,N‐dimethylformamide in casting solution, 13 min evaporation time and 0°C temperature of water bath for the gelation of the membrane, and the operating pressure and feed solution of (R,S)‐2‐phenyl‐1‐propanol were 0.2 MPa and 1.5 mg/mL, respectively, over 90% of enantiomeric excess (e.e.) and 44.2 (mg/m² h) of flux were obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Facile synthesis of hollow microspheres of polyaniline using poly(sodium 4‐styrenesulfonate) as dopant

In a conventional chemical oxidative polymerization of aniline in poly(sodium 4‐styrenesulfonate) aqueous solution, hollow microspheres of polyaniline were easily prepared, instead of common particles. The morphology of the hollow microspheres was studied and confirmed using scanning electron microscopy and transmission electron microscopy. The molecular structure, room temperature conductivities and thermal stability of the resulting polyaniline were characterized using Fourier transform infrared spectroscopy, the standard DC four‐probe method, thermogravimetric analysis and differential thermal analysis. The influence of poly(sodium 4‐styrenesulfonate) and aniline on the morphology and physical properties of the resulting polymer were investigated. The results showed that the proper ratio of poly(sodium 4‐styrenesulfonate) and aniline was a critical factor in the synthesis of hollow microspheres, which may be related to the chemical structure of poly(sodium 4‐styrenesulfonate) as polyanion and of polyaniline as polycation and the electrostatic interaction between them in the doping process. A possible formation mechanism is proposed in this work. © 2013 Society of Chemical Industry     

Dispersion polymerization of acrylamide with 2‐acrylamido‐2‐methyl‐1‐propane sulfonate in aqueous solution

The copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propane sulfonate (AMPS) was synthesized through the free radical dispersion polymerization in an aqueous solution of ammonium sulfate and in the presence of poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonate) as stabilizer. The average particle size of the copolymer ranged from 1 to 4 μm, and the molecular weight was from 2.0 × 10⁶ to 7.0 × 10⁶ g mol^?1. By analyzing apparent viscosity and particle size, the swelling property of the dispersion copolymer was studied. When the dispersion was diluted with salt water in which the ammonium sulfate concentration kept equal with that of the original dispersion, particle size and particle size distribution of the diluted dispersion changed a little, compared with that of the original dispersion. While diluted with deionized water, particle size and particle size distribution could expand several times. The effects of varying concentrations of the stabilizer, the monomer, the salt and the initiator on particle size, and molecular weight of the copolymer were investigated, respectively. The reaction conditions for preparing stable dispersion were concentrations of 20–28% of the salt, 6–14% of monomers, and 1.8–2.7% of the stabilizer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2379–2385, 2006     

Incorporation of 4‐aminobenzene functionalized multi‐walled carbon nanotubes in polyaniline for application in formic acid electrooxidation

Incorporation of carbon nanotubes (CNTs) in conducting polymer can lead to new composites with enhanced electrical and mechanical properties. However, the development of such composites has been hampered by the inability to disperse CNTs in polymer matrix due to the lack of chemical compatibility between polymers and CNTs. Covalent sidewall functionalization of carbon nanotube provides a feasible route to incorporate carbon nanotube in polymer. In this work, 4‐aminobenzene groups were grafted onto the surface of multi‐walled carbon nanotube (MWNT) via C? C covalent bond. Polyaniline (PANI)/MWNT composites were fabricated by electrochemical polymerization of aniline containing well‐dissolved functionalized MWNTs. The obtained composites can be used as catalyst supports for electrooxidation of formic acid. Cyclic voltammogram results show that platinum particles deposited in PANI/MWNT composite films exhibit higher electrocatalytic activity and better long‐term stability towards formic acid oxidation than that deposited in pure PANI films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Introduction of methanol in the formation of polyaniline nanotubes in an acid-free aqueous solution through a self-curling process

This study reports the synthesis of polyaniline (PANI) nanotubes with the introduction of methanol in aqueous solutions. SEM images indicate that well-dispersed PANI nanotubes are produced when the concentration of methanol increases up to 1 M. On the other hand, polymers primarily form irregular agglomerates when only monomers and oxidant are used in the absence of methanol. Transmission electron microscopy (TEM) reveals that the resulting nanotubes have an outer diameter of about 200 nm and an inner diameter of 0-50 nm. Fourier transform infrared (FT-IR) spectra indicate that the intermediate samples obtained at a reaction time of around 60 min have a structure consisting of a head of phenazine-like units and a tail of para-linked aniline units. Ultraviolet-visible (UV-vis) spectra indicate that emeraldine salt polyaniline (ES-PANI) appears in sequence as the reaction time reaches 75 min. At the time interval of 60-75 min, the self-curling behavior of the PANI intermediates first appears at 60 min, and PANI nanotubes can be observed starting at 75 min. This is the first study to observe this self-curling process and propose that it explains the formation of PANI nanotubes. Noteworthily, the nanotubes transform into irregular agglomerates after a de-doping process.     

Influence of reaction conditions on the formation of nanotubes/nanoparticles of polyaniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid and applications as electrostatic charge dissipation material

BACKGROUND: Poly(1‐amino‐2‐naphthol‐4‐sulfonic acid) and its copolymers with aniline are a new class of conducting polymers which can acquire intrinsic protonic doping ability, leading to the formation of highly soluble self‐doped homopolymers and copolymers. Free ? OH and ? NH₂ groups in the polymer chain can combine with other functional groups that could be present in protective paints which can thus be successfully used as antistatic materials. RESULTS: This paper reports the formation of nanotubes of polyaniline on carrying out oxidative polymerization of aniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) in p‐toluenesulfonic acid (PTSA) as an external dopant. The presence of ? SO₃H groups in the ANSA comonomer allows the copolymer to acquire intrinsic protonic doping ability. The polymerization mechanism was investigated by analysing the ¹H NMR, ¹³C NMR, Fourier transform infrared and X‐ray photoelectron spectra of the copolymers and homopolymers, which revealed the involvement of ? OH/? NH₂ in the reaction mechanism. Scanning and transmission electron microscopy showed how the reaction route and the presence of a dopant can affect the morphology and size of the polymers. Static decay time measurements were also carried out on conducting copolymer films prepared by blending of 1 wt% of copolymers of ANSA and aniline with low‐density polyethylene (LDPE) which showed a static decay time of 0.1 to 0.31 s on dissipating a charge from 5000 to 500 V. CONCLUSION: Copolymers of ANSA with aniline were synthesized in different reaction media, leading to the formation of nanotubes and nanoparticles of copolymer. Blends of 1 wt% of PTSA‐ and self‐doped copolymers of ANSA and aniline with LDPE can be formulated into films with effective antistatic properties. Copyright © 2009 Society of Chemical Industry     

Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β‐naphthalenesulfonic acid (β‐NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2–5 °C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β‐NSA and the molar ratio of β‐NSA to aniline. By this means the size of the β‐NSA–aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline‐filled micelles with β‐NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV‐visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. © 2014 Society of Chemical Industry     

The effect of initiator‐to‐monomer ratio on the properties of the polybutadiene‐ol synthesized by free radical solution polymerization of 1,3‐butadiene

Polybutadiene‐ol was synthesized by solution radical polymerization of 1,3‐butadiene in the presence of hydrogen peroxide as initiator and 2‐propanol as solvent. The ratio of initiator to monomer molar concentration, [I₀]/[M₀], was varied while temperature, reaction time and the type and amount of solvent were kept constant. The effects on the M_n; M_w; M_v; PDI, OH‐number and functionality of the synthesized polyols were studied. By taking several samples during a polymerization batch and analyzing them, the time of reaction was chosen as 100 min, after which the PDI changed dramatically. M_n decreased exponentially with increasing [I₀]/[M₀] according to the relationship M_n = 565.55 ([I₀]/[M₀])^?0.7553. The decrease observed in M_w gradually levelled off with increasing [I₀]/[M₀] and molecular weight distribution broadened at larger values of [I₀]/[M₀]. The OH‐number increases with [I₀]/[M₀]. In addition to the number‐average molecular weight, functionality is dependent on the number of hydroxyl‐terminated chain radicals in the reaction medium. Copyright © 2003 Society of Chemical Industry     

Effect of thermal aging on electrical conductivity of the 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid‐doped polyaniline fiber

The thermal characteristics of inherently conductive polyaniline (PANi) fiber have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fibers show five major weight losses at ∼100°C, 165°C, 215°C, 315°C, and 465°C, which are associated with the removal of moisture, residual solvent, decompositions of the sulfonic acid and degradation of PANi fiber, respectively. The 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSA) that dopes the PANi (in fiber form) performs two‐stage decompositions. The conductivity of the drawn fibers aged at 50°C, 100°C, 150°C, and 190°C under vacuum for various periods of time decreases, particularly at temperatures higher than 100°C. The reduction in conductivity of the fiber aged at temperatures lower than 100°C is mainly due to the evaporation of the residual solvent (15–20% in the as‐spun fiber). Further decrease in conductivity of the fiber aged at temperatures higher than 100°C is caused by the decomposition of the dopant AMPSA. The temperature‐dependent conductivity of the fiber was measured at 15 K (−258.5°C) to 295 K (21.5°C). The conductivity of both aged and un‐aged fibers is all temperature activated, however, the conductivity of the un‐aged fibers is higher than that of the aged fibers. Although a negative temperature coefficient was observed in the temperature range from 240 K (–24.5°C) to 270 K (–3.5°C) for the un‐aged fibers, it was disappeared when the fibers were thermal aged at 100°C for 24 h in vacuum oven. These results indicate that the residual solvent trapped inside the fiber enhanced the electrical conductivity of the fibers and its “metallic” electrical conductivity at temperatures ∼263 K (–10°C). © 2001 John Wiley & Sons, Inc. † J Appl Polym Sci 79: 2503–2508, 2001     

Characterization of macroporous 1‐vinyl‐2‐pyrrolidone copolymers obtained by suspension polymerization

Radical suspension copolymerization of 1‐vinyl‐2‐pyrrolidone (VP) with three different cross‐linkers: divinylbenzene (DVB), trimethylolpropane trimethacrylate (TRIM), and di(methacryloxymethyl) naphthalene (DMN) was used to prepare macroporous microspheres. During the copolymerization, the mixture of toluene and n‐dodecane as a pore‐forming diluent was used. All samples were characterized in terms of particle size and distribution, nitrogen content, specific surface area total pore volume, and pore size distribution. It was found that specific surface area of the obtained beads is strongly dependent on the diluent system and the type of cross‐linker and achieves value from 27 to 845 m²/g. To determine the influence of chemical structure of cross‐linkers on the selectivity and polarity of the copolymers, inverse gas chromatography was applied. In addition, VP–DVB and VP–DMN copolymers were modified by sulfonation into cation‐exchangers with cation exchange capacity equal 1.98 and 2.31 mmol/g, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical reinforcement of poly(1‐butene) using polypropylene‐grafted multiwalled carbon nanotubes

The mechanical properties of poly(1‐butene) reinforced by pristine multiwalled carbon nanotubes (MWNTs) and polypropylene‐grafted MWNTs (PP‐g‐MWNTs) were evaluated. The incorporation of pristine MWNTs to PB led to an improvement in stiffness, but not in strength, ductility, and toughness. In comparison, PP‐g‐MWNTs were able to improve the stiffness, strength, and toughness of PB significantly, without compromising the ductility. The mechanical properties of PB improved with increasing amount of PP‐g‐MWNTs up to an effective MWNT content of 1.5 wt%. Further increase in the effective MWNT content led to a downturn in mechanical properties due to the existence of MWNTs bundles as observed by microscopy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The analysis of solubility,absorption kinetics of CO2 absorption into aqueous 1‐diethylamino‐2‐propanol solution

In this present work, the CO₂ absorption performance of aqueous 1‐diethylamino‐2‐propanol (1DEA2P) solution was studied with respect to CO₂ equilibrium solubility, absorption kinetics, and absorption heat. The equilibrium solubility of CO₂ in 2M 1DEA2P solution was measured over the temperature range from 298 to 333 K and CO₂ partial pressure range from 8 to101 kPa. The absorption kinetics data were developed and analyzed using the base‐catalyzed hydration mechanism and artificial neural network models (radial basis function neural network [RBFNN] and back‐propagation neural network [BPNN] models) with an acceptable absolute average deviation of 10% for base‐catalyzed hydration mechanism, 2.6% for RBFNN model and 1.77% for BPNN model, respectively. The CO₂ absorption heat of 1DEA2P was estimated to be ?43.6 kJ/mol. In addition, the ions (1DEA2P, 1DEA2PH⁺, , CO₃^2?) speciation plots of the 1DEA2P‐CO₂‐H₂O system were developed to further understand the reaction process of 1DEA2P with CO₂. Based on a comparison with conventional amines (e.g., MEA, DEA, MDEA) and alternative amines (i.e., 1DMA2P and 4‐(diethylamino)?2‐butanol [DEAB]), 1DEA2P exhibited good performance with respect to CO₂ equilibrium solubility, reaction kinetics, and CO₂ absorption heat. Meanwhile, the overall evaluation of 1DEA2P for application in CCS in terms of absorption and desorption is presented, giving helpful information for the screening of these novel amines. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2694–2704, 2017     

Self‐doping of polyaniline prepared with the FeCl3/H2O2 system and the origin of the Raman band of emeraldine salt at around 1375 cm−1

Stepwise addition of H₂O₂ in small portions into the polymerization mixture reduces the number of defects in polyaniline (PANI) prepared with the Fe³⁺/H₂O₂ system, although it does not eliminate them completely. PANIs slightly self‐doped with phenolic groups are thus obtained, which show conductivity from 2.65 to 0.38 S cm^?1 as the total H₂O₂/aniline mole ratio is increased from 0.125 to 1.25. The conductivity shows a good correlation with the A_B/A₉₀₀ UV?visible absorbance ratio of the PANI emeraldine salt form (PANI ES), much better than with the A_B/A_Q ratio of the corresponding emeraldine base form. This corresponds well with the assignment of the band at 900 nm to polaronic transitions. Partial self‐doping of PANIs with weakly acidic phenolic groups allowed evidence to be obtained for the assignment of Raman bands at 1370 cm^?1 and 734 cm^?1 (for λ_exc = 780 nm) to vibrational modes of highly localized polarons. The presence of the band at 880 cm^?1 in the IR spectra of these PANI ES samples that are totally free of sulfate ions proves that this band is associated with a vibrational mode of PANI ES and need not be assigned to a mode of HSO₄^? ions, as has been suggested by some authors. © 2015 Society of Chemical Industry     

Homogeneous synthesis of linoleic acid‐grafted chitosan oligosaccharide in ionic liquid and its self‐assembly performance in aqueous solution

A water‐soluble amphiphilic derivative of chitosan oligosaccharide (COS) modified with linoleic acid (LA)‐grafted COS (LCOS) has been synthesized in the ionic liquid 1‐butyl‐3‐methylimidazolium acetate ([BMIM]Ac). The effects of the ionic liquid on the degree of substitution (DS), surface activity, and self‐assembly behavior of LCOS have been investigated. The results showed that the ionic liquid homogeneous system led to a relatively higher DS compared with the product synthesized in a traditional organic solvent. Furthermore, the LCOS synthesized in the ionic liquid had better surface activity (cmc = 1.1 × 10^?4 g·mL^?1), and could also self‐assemble into nanomicelles with better‐defined spherical shape and a narrower particle size distribution (30–40 nm) in aqueous solution. These results suggest that an effective and environmentally friendly synthesis method for COS derivatives has been established and, moreover, the obtained LCOS micelles meet the basic requirements for use as an improved drug transduction vector. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41727.     

Flow characteristics of thermo‐responsive microspheres in microchannel during the phase transition

To probe into the flow and aggregation behaviors of thermo‐responsive microspheres in microchannel during the phase transition, the flow characteristics of monodisperse poly(n‐isopropylacrylamide) (PNIPAM) microspheres in microchannel with local heating are investigated systematically. When the fluid temperature in the microchannel increases across the lower critical solution temperature (LCST), the PNIPAM microspheres finish the phase transition within 10 s and are easily get aggregated during the phase transition. The diameter ratio of microsphere to microchannel, number of microspheres, initial distance between microspheres, and flow direction of fluid in microchannel, are key parameters affecting the flow and aggregation behaviors of the microspheres in microchannel during the phase transition. If a proper combination of these parameters is designed, the microspheres can aggregate together during the phase transition and stop automatically at a desired position in the microchannel by local heating, which is what the targeting drug delivery system expected. © 2009 American Institute of Chemical Engineers AIChE J, 2009