Polyaniline–organoclay nanocomposites as curing agent for epoxy: Preparation and characterization

Polyaniline (PANI)–organoclay/Epoxy (EP) nanocomposites were prepared. PANI–organoclay nanocomposites were used as curing agent for EP. Organoclay was prepared by an ion exchange process between sodium cations in MMT and NH₃⁺ groups in polyoxypropylene (D₂₃₀). PANI–organoclay nanocomposite was synthesized by in situ polymerization of aniline in (14 wt%) organoclay. Infrared spectra and differential scanning calorimetry confirm the curing of EP. The absence of d₀₀₁ diffraction band of organoclay in the nanocomposites was observed by X‐ray diffraction. The structure argument was further supported by scanning electron microscopy and transmission electron microscopy. Electrical conductivity of the nanocomposites within the range 2.1 × 10⁻⁷–3.2 × 10⁻⁷ S/cm depending on the concentration of the PANI/D₂₃₀‐MMT. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The effect of polyoxypropylene‐montmorillonite intercalates on polymethylmethacrylate

Polymethylmethacrylate (PMMA)‐layered silicate nanocomposites have been prepared by in situ polymerization of commercial type of methylmethacrylate monomer (MMA), for denture base material, into organoclay. Organoclay was prepared through an ion exchange process between sodium cations in montmorillonite and NH₃⁺ groups in polyethertriamine hydrochloride and polyoxypropylene triamine hydrochloride with different molecular weight (5000, 440). X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the structure of the resulting composites. Both intercalated and exfoliated nanocomposites were obtained depending on the type and amount of organoclay. The thermal decomposition temperatures of the nanocomposites were found to be higher than that of pristine polymer. PMMA was strongly fixed to inorganic surfaces, due to cooperative formation of electrostatic bonding between NH₃⁺ group and negatively charged surface of layered silicate and amide linkage between PMMA and polyethertriamine or polyoxypropylene triamine. The effect of the organoclay on the hardness, toughness, tensile stress, and elongation at break of the polymer was studied and was compared with pristine polymer. The hardness and Izod impact strength of PMMA‐organoclay nanocomposites were enhanced with the inclusion of clay. Tensile properties appear to be enhanced at certain organoclay content. However, the water absorption is slightly higher than the pristine PMMA. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Polyaniline/Montmorillonite Nanocomposites Obtained by In Situ Intercalation and Oxidative Polymerization in Cationic Modified-Clay (Sodium, Copper and Iron)

Polyaniline/montmorillonite nanocomposites (PANI/M) were obtained by intercalation of aniline monomer into M modified with different cations and subsequent oxidative polymerization of the aniline. The modified-clay was prepared by ion exchange of sodium, copper and iron cations in the clay (Na–M, Cu–M and Fe–M respectively). Infrared spectroscopy confirms the electrostatic interaction between the oxidized PANI and the negatively charged surface of the clay. X-ray diffraction analysis provides structural information of the prepared materials. The nanocomposites were characterized by transmission electron microscopy and their thermal degradation was investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites have higher thermal stability than pure PANI. The electrical conductivity of the nanocomposites increased between 12 and 24 times with respect to the pure M and this increase was dependent on the cation-modification. The electrochemical behavior of the polymers extracted from the nanocomposites was studied by cyclic voltammetry and a good electrochemical response was observed.     

Synthesis and antimicrobial activity of the Schiff base from polyoxyalkylene‐montmorillonite nanocomposites and aldehydes

Vanillin (4‐hydroxy‐3‐methoxy benzaldehyde) and 5‐formylamino salicylic acid microbicides were reacted with polyoxyalkylene‐montmorillonite (D_230–2000‐MMT) nanocomposites. The microstructure of these Schiff base nanocomposites was characterized by TEM and XRD. D_230–2000‐MMT nanocomposites were prepared by an ion exchange process of sodium montmorillonite (Na‐MMT) and NH₃ ⁺ groups in polyoxyalkylene amine hydrochloride with three different molecular masses of D₂₃₀, D₄₀₀, and D₂₀₀₀. Wide‐angle X‐ray diffraction confirms the intercalation of the polymer between the silicate layers. Electrostatic interaction between the positively charged NH₃ ⁺ groups and the negatively charged surface of MMT was observed. The nanocomposites were tested for antimicrobial activity against the Gram‐negative bacteria (Escherichia coli NCIM 2065), Gram‐positive bacteria (Bacillus subtillus ATCC), and fungi (Candida albicans SC5314 and Cryptococcus neoformans). The D₂₀₀₀‐MMT/vanillin Schiff base nanocomposite strongly inhibited the growth of all microorganisms that can be used in different applications. The amount of loaded polymer and the structure of the nanocomposite play an important role in inhibiting the bacterial and fungal strains. It is found that the Schiff base nanocomposite affect the morphology, oxygen consumption, and the release of cytoplasmic constituents such as potassium (K⁺), sodium (Na⁺), and calcium (Ca²⁺) ions leading to death of the cells. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Organomodification of montmorillonite and its effects on the properties of poly(butylene succinate) nanocomposites

The pristine sodium montmorillonite (MMT) was organically modified with hexadecyltrimethylammonium bromide (HTAB) at different contents. The organoclay was characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, energy dispersive X‐ray techniques, and thermogravimetric analysis. Then, poly(butylene succinate) (PBS) nanocomposites were prepared by melt‐mixing process using maleic anhydride‐grafted PBS (PBS‐g‐MA) as compatibilizer. It was found that the mechanical properties of PBS nanocomposites filled with organoclay were apparently higher than that of the nanocomposite filled with MMT. This is attributed to the better filler–matrix interactions between PBS and the organoclay and the better filler dispersion. This is verifiable through the XRD, scanning electron microscopy, and transmission electron microscopy. The addition of PBS‐g‐MA further improved the mechanical properties. It was also found that our laboratory synthesized organoclay modified with HTAB has provided a better reinforcing efficiency when compared with the commercial octadecylamine‐modified organoclay. Besides that the thermal properties of PBS nanocomposites were studied through differential scanning calorimetry. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Ferromagnetic polyaniline/TiO2 nanocomposites

Novel ferromagnetic semiconducting polyaniline PANI/TiO₂ nanocomposites were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous medium, in the presence of colloidal TiO₂ nanoparticles (d ∼ 4.5 nm), without added acid. The morphological, magnetic, structural, and optical properties of the PANI/TiO₂ nanocomposites prepared at initial aniline/TiO₂ mole ratios 80, 40, and 20 were studied by scanning electron microscopy, superconducting quantum interference device, X‐ray powder diffraction, FTIR, Raman, and UV‐Vis spectroscopies. The emeraldine salt form of linear PANI chains as well as the presence of phenazine units, branched PANI chains, and anatase crystalline structure of TiO₂ in PANI/TiO₂ nanocomposites was confirmed by FTIR and Raman spectroscopies. The electrical conductivity of synthesized composites was ∼10⁻³ S cm⁻¹. The room temperature ferromagnetic response with coercive field of H_c ∼ 300 Oe and the remanent magnetization of M_r ∼ 4.35 × 10⁻⁴ emu/g was detected in all investigated PANI/TiO₂ nanocomposites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Facile synthesis of SBA-15/polyaniline nanocomposites with high electrochemical activity under neutral and acidic conditions

A facile synthesis of SBA-15/polyaniline (PANI) nanocomposites was developed via chemical polymerization in a pH 3 solution based on the electrostatic adsorption of positively charged anilinium ions on negatively charged SBA-15. X-ray diffraction, N₂ sorption isotherms, transmission electron microscopy and scanning electron microscopy characteristics indicated that PANI chains were distributed both on the inside and outside surfaces of the SBA-15 pores. A possible synthetic scheme for the creation of nanocomposites has been proposed. The SBA-15/PANI nanocomposites showed high, stable electrochemical activity in neutral and acidic conditions. The preliminary use of the SBA-15/PANI nanocomposites as an electroactive support for the selective detection of uric acid (UA) in the presence of a large excess of ascorbic acid (AA) demonstrates this material’s potential for use in electrochemical biosensors.     

Preparation and characterization of polyurethane–organoclay nanocomposites

Nanocomposite polyurethane (PU)–organoclay materials have been synthesized via in‐situ polymerization. The organoclay is first prepared by intercalation of tyramine into montmorillonite (MMT)‐clay through ion exchange process. The syntheses of polyurethane–organoclay hybrid films containing different ratios of clay were carried out by swelling the organoclay into diol and diamine followed by addition of diisocyanate and then cured. The nanocomposites with dispersed and exfoliated structure of MMT were obtained as evidenced by X‐ray diffraction and scanning electron microscope. X‐ray diffraction showed that there is no peak corresponding to d₀₀₁ spacing in organoclay with the ratios up to 20 wt%. SEM images confirmed the dispersion of nanometer silicate layers in the polyurethane matrix. Also, it was found that the presence of organoclay leads to improvement in the mechanical properties. The tensile strength was increased with increasing the organoclay contents to 20 wt% by 221% in comparision to the PU with 0% organoclay. POLYM. COMPOS. 28:108–115, 2007. © 2007 Society of Plastics Engineers     

Synthesis and properties of polyimide (containing naphthalene) nanocomposites with organo‐modified montmorillonites

2,7‐Bis(4‐aminophenoxy) naphthalene (BAPN), a naphthalene‐containing diamine, was synthesized and polymerized with a 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) to obtain a polyimide (PI) via thermal imidization. To enhance the thermal and mechanical properties of the polymer, PI–Montmorillonite (MMT) nanocomposites were prepared from a DMAc solution of poly(amic acid) and a DMAc dispersion of MMT, which were organo‐modified with various amounts of n‐dodecylamine (DOA) or cetylpyridium chloride (CPC). FTIR, XRD, and TEM (transmission electron microscopy) were used to verify the incorporation of the modifying agents into the clay structure and the intercalation of the organoclay into the PI matrix. Results demonstrated that the introduction of a small amount of MMT (up to 5%) led to the improvement in thermal stability and mechanical properties of PI. The decomposition temperature of 5% weight loss (T_d,5%) in N₂ was increased by 46 and 36°C in comparison with pristine PI for the organoclay content of 5% with DOA and CPC, respectively. The nanocomposites were simultaneously strengthened and toughened. The dielectric constant, CTE, and water absorption were decreased. However, at higher organoclay contents (5–10%), these properties were reduced because the organoclay was poorly dispersed and resulted in aggregate formation. The effects of different organo‐modifiers on the properties of PI–MMT nanocomposite were also studied; the results showed that DOA was comparable with CPC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Fabrication and microwave absorption properties of BaTiO3 nanotube/polyaniline hybrid nanomaterials

Hybrid nanomaterials consisting of BaTiO₃ nanotubes (BTO NTs) and polyaniline (PANI), hereafter denoted as BTO NT/PANI, were successfully prepared by a one‐step in situ oxidative polymerization process of aniline monomers in the presence of BaTiO₃ nanotubes, with ammonium persulfate as oxidant and hydrochloric acid as dopant. The structure and morphology of the nanocomposites were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. The conductivity property of the hybrid nanomaterials was also investigated. Compared with pure polyaniline, BTO NT/PANI hybrid nanomaterials exhibited enhanced reflection loss properties, which can even be further improved with appropriate electromagnetic impedance matching. More importantly, microwave‐absorbing properties of the nanocomposites can be simply modulated simply by controlling the BaTiO₃ NTs content of the absorber for the required frequency bands. Therefore, these composites may be used as lightweight andhighly effective microwave absorbers. POLYM. COMPOS., 2013 © 2013 Society of Plastics Engineers     

Investigation of corrosion protection performance of epoxy coatings modified by polyaniline/clay nanocomposites on steel surfaces

In this study, polyaniline (PANI) and polyaniline/clay nanocomposites were prepared via in situ oxidative polymerization. The morphology of nanocomposites structures was investigated by X-ray diffraction (XRD). The chemical structures of PANI and PANI/clay nanocomposites were examined via Fourier transform infrared (FT-IR) spectroscopy. Polyaniline-based pigments were introduced into epoxy paint and applied on steel substrates. The effect of clay addition and the type of clay cation, including Na⁺ in natural clay (MMT) and alkyl ammonium ions in organo-modified montmorillonite (OMMT), on the anticorrosion performance of epoxy-based coatings was investigated through electrochemical Tafel test, electrochemical impedance spectroscopy and immersion measurements in NaCl solution. The stability of the adhesion of the neat and modified epoxy coatings to the steel surface was also examined. The results indicated that introduction of PANI/OMMT nanocomposite into epoxy paint results in improved anticorrosion properties in comparison with PANI/MMT and neat PANI.     

Evaluation of amine functionalized polypropylenes as compatibilizers for polypropylene nanocomposites

The compatibilization effects provided by amine functionalized polypropylenes versus those of a maleated polypropylene, PP-g-MA, for forming polypropylene-based nanocomposites were compared. Amine functionalized polypropylenes were prepared by reaction of maleated polypropylene, PP-g-MA, with 1,12-diaminododecane in the melt to form PP-g-NH₂ which was subsequently protonated to form PP-g-NH₃⁺. Nanocomposites were prepared by melt processing using a DSM microcompounder (residence time of 10 min) by blending polypropylene and these functionalized materials with sodium montmorillonite, Na-MMT, and with an organoclay. X-ray and transmission electron microscopy plus tensile modulus tests were used to characterize those nanocomposites. Composites based on Na-MMT as the filler showed almost no improvement of tensile modulus compared to the polymer matrix using any of these functionalized polypropylenes, which indicated that almost no exfoliation was achieved. All the compatibilized nanocomposites using an organoclay, based on quaternary ammonium surfactant modified MMT, as the filler had better clay exfoliation compared to the uncompatibilized PP nanocomposites. Binary and ternary nanocomposites using amine functionalized polypropylenes had good clay exfoliation, but no advantage over those using PP-g-MA. The PP-g-MA/organoclay and PP/PP-g-MA/organoclay nanocomposites showed the most substantial improvements in terms of both mechanical properties and clay exfoliation.     

Liquid‐crystalline copolyester/clay nanocomposites

A series of novel polymer–clay nanocomposites, that is, liquid‐crystalline copolyester/montmorillonite (MMT) nanocomposites, were synthesized by the intercalation polycondensation of terephthalic acid, p‐acetoxy benzoic acid, and 1,2‐diacetoxy benzene in the presence of different organically modified montmorillonites (OMt's). The OMt's were prepared by the ion exchange of MMT with octadecylamine hydrochloride, p‐aminobenzoic acid hydrochloride, or lysine hydrochloride. X‐ray diffraction and transmission electron microscopy studies indicated that the inorganic cations in the MMT interlayers were already exchanged by organic onium ions and that the OMt intercalated with p‐aminobenzoic acid or lysine was good for obtaining more delaminated clay nanocomposites. The glass‐transition temperature and modulus of the nanocomposites increased compared with those of the pure polymer, whereas the isotropic temperature decreased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3155–3159, 2003     

Synthesis of conducting polyaniline‐montmorillonite nanocomposites via inverse emulsion polymerization in supercritical carbon dioxide

A new inverse emulsion polymerization and intercalation procedure in supercritical carbon dioxide (SCCO₂) was initially employed to synthesize polyaniline‐montmorillonite (PANI‐MMT) nanocomposites. The effect of chemical groups in MMT galleries on intercalation in SCCO₂ was investigated. The MMTs modified by different organic cationic surfactants were incorporated into the composite particles, and in unintercalated, partially delaminated or fully exfoliated state. The aminated MMT or fluorinated MMT were utilized to prepare conducting PANI‐MMT nanocomposites with highly concentrated (12–25 wt% loading to monomer), fully exfoliated MMT platelets in SCCO₂. The structure and morphology of PANI‐MMT nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffraction pattern (XRD), and transmission electron microscope (TEM). Thermogravimetry analysis (TGA) was performed to demonstrate the enhancement of thermal stability of the composites. SCCO₂ was shown to be more effective for impregnation, disaggregation and exfoliation of MMTs than isooctane, which indicates that SCCO₂ is an alternative solvent for synthesis of some intercalated composite materials, not only based on the environmental friendly characteristic of SCCO₂, but also owing to that SCCO₂ can play an important role in intercalative polymerization. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Polyurethane/clay nanocomposites foams: processing, structure and properties

Polyurethane (PU)/montmorillonite (MMT) nanocomposites were synthesized with organically modified layered silicates (organoclays) by in situ polymerization and foams were prepared by a batch process. Clay dispersion of polyurethane nanocomposites was investigated by X-ray diffraction and transmission electron microscopy. The morphology and properties of PU nanocomposites and foams greatly depend on the functional groups of the organic modifiers, synthesis procedure, and molecular weight of polyols because of the chemical reactions and physical interactions involved. Silicate layers of organoclay can be exfoliated in the PU matrix by adding hydroxyl and organotin functional groups on the clay surface. The presence of clay results in an increase in cell density and a reduction of cell size compared to pure PU foam. In the polyurethane with high molecular weight polyol, a 6 °C increase in T_g, 650% increase in reduced compressive strength, and 780% increase in reduced modulus were observed with the addition of 5% organically treated clays. Opposite effects were observed in PU nanocomposite foams with highly crosslinked structure. The interference of the H-bond in the presence of clay is probably the reason.     

Water‐dispersible nanocomposites of polyaniline and montmorillonite

The polymerization of aniline (ANI) in aqueous medium in the presence of (NH₄)₂S₂O₈ and montmorillonite (MMT) resulted in the formation of a nanocomposite (PANI–MMT). The inclusion of PANI in the composite was confirmed by FTIR studies. The extent of PANI loading in the composite increased with ANI concentration at a fixed oxidant/MMT amount and with the oxidant amount at a fixed ANI and MMT weight, but decreased with an MMT amount at a fixed ANI and oxidant level. TGA revealed a higher stability for the PANI–MMT composite relative to PANI and confirmed a PANI loading of ca. 51% in the composite. The conductivity increased in all the cases. XRD analysis revealed no expansion of the d₀₀₁ spacing at 9.8 Å, implying no intercalation of PANI within the MMT layers. Scanning electron micrography studies revealed interesting morphological features for the composites. Transmission electron micrography analysis revealed distinctive features and confirmed the formation of PANI–MMT composite particles of diameters in the 300‐ to 400‐nm range. These composites could be obtained as stable colloids in the presence of poly (N‐vinyl pyrrolidone) under selective conditions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2948–2956, 2000     

Synthesis and characterization of polyurethane/organo-montmorillonite nanocomposites

Polyurethane (PU)/organo-montmorillonite nanocomposites were prepared by in situ polymerization of toluene diisocyanate and butanediol in the presence of different contents of organo-montmorillonite (9–18 mass%). Organo-montmorillonite were prepared by an ion exchange process of sodium montmorillonite with –NH₃⁺ groups in polyoxyalkylene amine hydrochloride with two different molecular masses of 403 and 5000. To change the degree of surface modification, sodium montmorillonite was reacted with polyoxyalkylene amine hydrochloride in equivalent ratios (1:1 and 1:2). Dimethyl formamide (DMF) was used as a swelling agent for the prepared organo-montmorillonite. Different nanocomposite structures, depending on the molecular mass of the polyoxyalkylene and the degree of surface modification of montmorillonite were studied. The results of X-ray analysis and transmission electron microscopy showed that the organo-montmorillonite with polyoxyalkylene of higher molecular mass (T₅₀₀₀) produced the exfoliated PU nanocomposites; (T₄₀₃), led to an intercalated structure. Nanocomposites exhibited lower water adsorption values and higher thermal stability than that of pure PU₀. In addition, the hardness of the nanocomposites was measured.     

Ion-dipole interactions in the dispersion of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) copolymer

The dispersion characteristics of organoclay nanocomposites based on polystyrene-block-poly(2-vinylpyridine) (S2VP diblock) copolymer were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (NMR) spectroscopy. For the investigation, S2VP diblock copolymers having three different compositions were synthesized via sequential anionic polymerization. Each S2VP diblock copolymer was used to prepare nanocomposites by solution blending with natural clay (montmorillonite, MMT) or commercial organoclays (Cloisite 30B, Cloisite 10A, Cloisite 15A, and Cloisite 25A from Southern Clay Products). All four organoclays employed were treated with a surfactant having quaternary ammonium salt with N⁺ ion. It was found, via TEM and XRD, that the nanocomposites with MMT show very poor dispersion characteristics regardless of block copolymer composition. However, the block copolymer composition was found to have a profound influence on the dispersion characteristics of the nanocomposites with an organoclay. Specifically, the nanocomposites based on S2VP-5 having 5 wt% poly(2-vinylpyridine) (P2VP) block gave rise to a very high degree of dispersion, irrespective of the chemical structure of the surfactant residing at the surface of the organoclay employed, whereas the dispersion characteristics of the nanocomposites became progressively poorer as the amount of P2VP block in an S2VP diblock copolymer increased from 5 to 25 wt% and to 56 wt%. The observed dispersion characteristics were explained by hypothesizing the presence of ion-dipole interactions between the positively charged N⁺ ions in the surfactant residing at the surface of the organoclay nanoparticles and the dipoles in the P2VP block of S2VP diblock copolymers. The validity of this hypothesis was confirmed using solid-state NMR spectroscopy, by determining the dependence of the composition of S2VP diblock copolymer on the extent of ion-dipole interactions and thus on the dispersion characteristics of the nanocomposites prepared.     

Thermal and Barrier Properties of Organoclay-filled Polysulfone Nanocomposites

Organo-modified fluorohectorite (OFH) clay-filled polysulfone (PSf) nanocomposites were prepared by a solution casting method. The dispersion of OFH clay in PSf nanocomposites was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Thermal analysis revealed that incorporation of organoclay increased the thermal stability and glass transition temperature (T_g) of nanocomposites. The barrier properties of the nanocomposites studied were found to be significantly improved. It is worth mentioning that the improved thermal stability and barrier performance of these nanocomposites with the addition of organoclay in PSf matrix obviously offers immense potential in industrial and automobile applications.     

The Nucleating Effect of Montmorillonite on Crystallization of PET/Montmorillonite Nanocomposite

Poly(ethylene terephthalate) (PET)/montmorillonite (MMT) nanocomposites were prepared by solution intercalation method. The clay was organo-modified with intercalation agent of cetyltrimetylammonium chloride (CMC). XRD showed that the layers of MMT were intercalated by CMC. Four nanocomposites with organoclay contents of 1, 5, 10, and 15 wt% were prepared by solution blending. XRD showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. The nucleating effect of organoclay is investigated using differential scanning calorimetry (DSC) analysis. Clay behaves as a nucleating agent and enhances the crystallization rate of PET. Maximum enhancement in crystallization rate for the nanocomposites was observed in blends containing ca. 10 wt% of clay in the range of 1–15 wt%. According to transmission electron microscopy (TEM), the organoclay particle was highly dispersed in the PET matrix without a large agglomeration of particles for low organoclay content (5 wt%). Agglomerated structure did form in the PET matrix at 15 wt% organoclay content.