Simple Preparation of Sulfate Anion‐Doped Polyaniline‐Clay Nanocomposites by an Environmentally Friendly Mechanochemical Synthesis Route

Summary: Conducting polyaniline (PANI) and montmorillonite (MMT) nanocomposites were prepared from aniline sulfate and MMT by a mechanochemical synthesis route. X‐Ray diffraction analysis confirmed that, by controlling the aniline sulfate content, mechanochemical synthesis led to two types of different formations. After polymerization, the mechanochemical route synthesized much more PANI between the clay layers compared to a solution method. The electrical conductivities of the synthesized PANI‐MMT nanocomposites in pressed pellets ranged in the order of between 10⁻⁴ and 10⁻³ S · cm⁻¹.

X‐ray powder diffraction patterns of the intercalation products prepared by grinding montmorillonite with various amounts of Ani‐SO₄ in a mortar.     

Zero‐order kinetics of the thermal degradation of polypropylene/clay nanocomposites

The thermal degradation kinetics of polypropylene/clay microcomposites and nanocomposites were studied by thermogravimetric analysis. In comparison with pure polypropylene, the reaction order of the degradation of the composites became zero‐order, and the activation energy increased dramatically. The zero‐order kinetics were associated with the acidic sites (H⁺) created on the clay layers, whereas the increase in the activation energy was coupled with the shielding effect of clay. The kinetic analysis could provide additional mechanistic clues concerning the thermal stability and flammability of polymer/clay nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3713–3719, 2005     

Synthesis of polybenzoxazine/clay nanocomposites by in situ thermal ring‐opening polymerization using intercalated monomer

A new class of polybenzoxazine/montmorillonite (PBz/MMT) nanocomposites has been prepared by the in situ polymerization of the typical fluid benzoxazine monomer, 3‐pentyl‐5‐ol‐3,4‐dihydro‐1,3‐benzoxazine, with intercalated benzoxazine MMT clay. A pyridine‐substituted benzoxazine was first synthesized and quaternized by 11‐bromo‐1‐undecanol and then used for ion exchange reaction with sodium ions in MMT to obtain intercalated benzoxazine clay. Finally, this organomodified clay was dispersed in the fluid benzoxazine monomers at different loading degrees to conduct the in situ thermal ring‐opening polymerization. Polymerization through the interlayer galleries of the clay led to the PBz/MMT nanocomposite formation. The morphologies of the nanocomposites were investigated by both X‐ray diffraction and transmission electron microscopic techniques, which suggested the partially exfoliated/intercalated structures in the PBz matrix. Results of thermogravimetric analysis confirmed that the thermal stability and char yield of PBz nanocomposites increased with the increase of clay content. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Characterization,morphology, thermal and mechanical properties of conductive polyaniline‐functionalized EPDM elastomers obtained by casting

Conductive elastomeric blends based on ethylene–propylene–5‐ethylidene–2‐norbornene terpolymer (EPDM) and polyaniline doped with 4‐dodecylbenzenesulfonic acid [PAni(DBSA)] were cast from organic solvents. Functionalization of the elastomer was promoted by grafting with maleic anhydride. Vulcanization conditions were optimized with an oscillating disk rheometer. The conductivity, morphology, thermal stability, compatibility, and mechanical behavior of the obtained mixtures were analyzed by in situ direct current conductivity measurements, atomic force microscopy, transmission electron microscopy, wide‐angle X‐ray scattering, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis, stress–strain and hysteresis tests. The vulcanization process was affected by temperature, the PAni content, and maleic anhydride. A reinforcement effect was promoted by the vulcanizing agent. The formation of links between the high‐molar‐mass phases and oligomers of PAni(DBSA) in the elastomeric matrix enhanced the thermal stability and ultimate properties of the blends. By the appropriate control of the polymer blends' composition, it was possible to produce elastomeric materials with conductivities in the range of 10^?5–10^?4 S · cm^?1 and excellent mechanical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1767–1782, 2004     

Insertion of Polypyrrole Chains into Montmorillonite Galleries by a Solvent‐Free Mechanochemical Route

Summary: Non‐ionic pyrrole was directly intercalated into unmodified montmorillonite (MMT) and organically modified MMT galleries by adsorption, and subsequently polymerized within the interlamellar spaces by a mechanochemical route under solvent‐free conditions. XRD analysis revealed the successful intercalation of pyrrole into unmodified MMT and organically modified MMT clay galleries by mechanochemical grinding. After in situ polymerization, the XRD and FT‐IR analyses confirmed the insertion of polypyrrole chains between both MMT galleries.

X‐ray powder diffraction patterns of (A) pyrrole‐intercalated MMT and (B) pyrrole‐intercalated C18‐MMT.     

Structure and thermal behavior of metastable sillenites prepared by mechanochemical synthesis

The structure and thermal behavior of metastable solid solutions with nominal compositions Bi₂PbO₄, Bi₄HgO₇, Bi₁₂TlO_19.5, and Bi₁₂Cd_0.7O_18.7 with the sillenite structure obtained by mechanochemical treatment in a planetary mill (thermal decomposition of the metastable Bi₄CdO₇ phase with a bcc structure above 700 K) have been studied. The large Pb²⁺ atoms occupy up to ~30% positions in the sillenite structure (Hg²⁺ and Hg(1) occupy up to ~15% of (24f) positions). The (2a) sites are partially occupied by bismuth with a minor shift along the [111] axis and are transformed into the (8c) site, forming an umbrella structure with c.n. 3. The relatively small Cd²⁺and Tl³⁺ cations partially occupy the (2a) sites. During annealing, the metastable Pb-sillenites are partially stabilized with a loss of oxygen and increasing content of bismuth. Sillenite with a high content of lead retains its structure until it melts at 923 K. Cadmium sillenite reacts with CdO, passing into a rhombohedral structure at 900 K (30 K below the melting point). Mercury sillenite Bi₄HgO₇ decomposes with isolation of metallic mercury at ~600 K.Original Russian Text Copyright © 2004 by V. V. ZyryanovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 480–490, May–June 2004.     

Sulfonated polyaniline‐graphene oxide hybrids: Synthesis and effect of monomer composition on the electrochemical signal for direct DNA detection

A variety of sulfonated polyaniline‐graphene oxide (SPAN‐GNO) nanocomposites based on GNO, aniline (ANI) and m‐aminobenzenesulfonic acid (ABSA) are prepared via changing the mole ratio of ANI to ABSA for the comparison of DNA sensing behavior. Self‐signals of SPAN‐GNO are employed for estimating the effect of preparation conditions [component, monomer composition (mole ratio of ANI to ABSA), and reaction time] on DNA immobilization and hybridization detection. Then, we find herein that the mole ratio of ANI to ABSA plays a lead role over other factors on hybridization efficiency. Meanwhile, the parallel experiments using methylene blue as the classic indicator verifies this conclusion. The results show that, by comparison with other mole ratio SPAN‐GNO nanocomposites‐modified electrodes, the mole ratio (2:3) exhibits the widest dynamic detection range from 1.0 × 10^?14 to 1.0 × 10^?6 M, as well as the lowest detection limit (3.06 × 10^?15 M). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1762–1773     

Crystallization behavior of clay nanocomposites prepared from a degradable alternating copolyester constituted by glycolic acid and 6‐hydroxyhexanoic acid

An exfoliated nanocomposite was prepared by the film‐casting technique from C25A organo‐modified clay and a new biodegradable polyester derived from glycolic acid and 6‐hydroxyhexanonoic acid. This polyester has a sequential monomer distribution and high crystallinity, allowing a detailed study of its isothermal crystallization. The influence of the clay on the crystallization behavior was investigated by optical microscopy, simultaneous SAXS/WAXD synchrotron radiation and FTIR spectroscopy. Primary nucleation and crystal growth rate decreased significantly with the incorporation of nanoparticles. In addition, the overall crystallization rate of the nanocomposite was logically lower than that of the neat polyester. Bulk crystallizations were modeled from FTIR data with the Avrami equation. The results showed spherulite growth geometry and predetermined (heterogeneous) nucleation for both samples. Morphological studies revealed that both the crystal and the amorphous layer thicknesses were influenced by the presence of silicate layers. The overall percentage of crystallinity and the size of crystalline domains decreased with the addition of the highly miscible organoclay. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 33–46, 2010     

Equilibrium thermal behavior and morphology of organophilic montmorillonite/poly(ε‐caprolactone) nanocomposites

With differential scanning calorimetry, we have demonstrated a peculiar behavior under equilibrium conditions of neat poly(ε‐caprolactone) and its organophilic montmorillonite nanocomposites. In particular, in the determination of the equilibrium melting temperature by the extrapolation of the data of the melting temperature (T_m) versus the crystallization temperature (T_c), a bimodal trend has been observed. At the lower T_c's, the data of T_m follow a constant trend, whereas at the higher ones, the usual increasing trend has been obtained. Morphological observations by atomic force microscopy (AFM) have provided evidence of two different crystalline morphologies for the lower and higher T_c ranges. Moreover, AFM has shown that the thermal treatments strongly influence the clay dispersion in the polymer matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 22–32, 2006     

Preparation of polyaniline‐coated mesoporous carbon and its enhanced electrochemical properties

Polyaniline/MC (mesoporous carbon) composite was synthesized by in situ chemical polymerization method and was used as a new electrode material for supercapacitor. The composite was characterized by N₂ adsorption and scanning electron microscope. The electrochemical capacitance performance of the composite was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge tests with a three‐electrode system in a 10 wt% H₂SO₄ solution. The polyaniline/MC composite electrode shows much higher specific capacitance than pure MC electrode, which is attributed to the incorporation of polyaniline onto the pore surface of MC. Copyright © 2009 John Wiley & Sons, Ltd.     

Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles

The polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm^?1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008     

Novel polymer nanocomposites based on polystyrene and Ti‐functionalized polyhedral silsesquioxanes

Ti‐based polyhedral silsesquioxanes (Ti‐POSSs) have been prepared and dispersed in polystyrene (PS), by in situ polymerization, and the resulting materials have been characterized by several experimental techniques including both scanning (SEM) and transmission (TEM) electron microscopy, wide angle X‐ray diffraction (WAXD), X‐ray photospectroscopy (XPS), and thermogravimetric analysis (TGA/DTG). TEM and SEM analyses proved that PS nanocomposites of the samples based on heptaisobutyl‐Ti‐POSS (HEI‐Ti‐POSS) are formed, where HEI‐Ti‐POSS cages are directly linked to the macromolecules via Ti‐C bonds. The presence of HEI‐Ti‐POSS enhances the thermo‐oxidative stability of PS‐based nanocomposites and does not significantly affect the polymer molecular mass. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of Fe‐MMT on crosslinking and thermal degradation in silicone rubber/clay nanocomposites

In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of a novel benzoxazine monomer‐intercalated montmorillonite and the curing kinetics of polybenzoxazine/clay hybrid nanocomposites

Polybenzoxazine (PBZ), which has a structure similar to that of phenolic resin, is formed through the thermal self‐curing of benzoxazine, that is through a heterocyclic ring opening reaction that requires no catalyst and releases no condensation byproducts. We have used the solvent blending method to prepare PBZ/clay nanocomposites possessing various clay contents. We synthesized a monofunctional benzoxazine monomer (MBM) and then treated the clay with this intercalation agent. The results of X‐ray diffraction (XRD) analysis indicated that MBM intercalated into the galleries of the clay; the nanocomposite possessed an exfoliated structure at 3% clay content. To better understand the curing kinetics of the PBZ/clay nanocomposites, we performed dynamic and isothermal differential scanning calorimetry (DSC) measurements. We describe the thermodynamics of the curing process, using all three of the Kissinger, Ozawa, and Kamal models. The Kissinger and Ozawa methods gave fairly close results for the calculated activation energies, which decreased upon increasing the clay content. The Kamal method, based on an autocatalytic model, suggested a total reaction order of between 2.4 and 2.8. The glass transition temperature (T_g) decreased upon increasing the clay content. Thermogravimetric analysis (TGA) indicated that the nanocomposites have higher decomposition temperatures than does the pristine PBZ; this finding suggests an enhancement in their thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 347–358, 2006     

Preparation and characterization of vinylidene chloride‐co‐vinyl chloride copolymer/fluorinated synthetic mica nanocomposites I thermal and mechanical properties studies

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified fluorinated synthetic mica (MEE) (VDC‐VC/MEE) nanocomposites were prepared by melt blending of VDC‐VC copolymer with MEE, in the presence of dioctyl phthalate (DOP) which acted as a plasticizer and a cointercalating agent. The nanostructure, thermal, and dynamic mechanical properties of the VDC‐VC/MEE nanocomposites were studied by wide angle X‐ray diffractometer (WAXD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). It was found that partially intercalated and partially exfoliated structures coexisted in VDC‐VC/MEE nanocomposities. Below 8 wt % MEE content, the intercalation effect of nanocomposites decreased with increasing the MEE content. Under a nitrogen atmosphere, VDC‐VC/MEE nanocomposites exhibited a single step thermal degradation behavior. The nanostructure of VDC‐VC/MEE can effectively prevent volatile gases from being released, and thus enhances its thermal stability. The thermal stability of VDC‐VC/MEE nanocomposites is strongly related to the morphology of nanocomposites and the degraded composites structure. DMA revealed a significant improvement in the storage modulus within the testing temperature range. The increase in storage modulus depends on the MEE content, which is attributed to the dispersed phase morphology. The glass transition temperature of VDC‐VC/MEE nanocomposites is affected by the chain mobility in the nanocomposites rather than the aggregative morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1214–1225, 2008     

Morphological and thermal properties of ABS/montmorillonite nanocomposites using two different ABS polymers and four different montmorillonite clays

ABS/Clay nanocomposites were prepared using two ABS with different Acrylonitrile (AN) contents and four montmorillonite clays; a natural clay (CNa+) and three modified clays, Cloisites 10A, 20A, and 30B. The composites were prepared in a twin‐screw extruder. Results were analyzed considering the effect of clay and ABS type, on the clay dispersion, intercalation and exfoliation, as well as on the storage modulus and thermal stability of the nanocomposites. XRD and TEM confirm that when using an ABS with higher AN content (ABS2), a better dispersion and intercalation–exfoliation can be obtained. Cloisites 20A and 30B, respectively the one with greater initial intergallery spacing, but lower polarity and with smaller inter‐gallery spacing but greater polarity, produce the ABS nanocomposites with the greater intergallery spacing. Both ABS polymers have similar storage modulus and T_g and in both cases, the modulus increases with the 4 wt % clay. This increase is greater with the modified clays and slightly greater with the ABS2. T_g, from tan δ, increases very little with the 4 wt % clay, but again, this is slightly greater with ABS2. TGA and flammability tests show that the dispersed clay enhances the thermal stability and that the ABS with higher AN content produces a greater increase in fire retardancy. Tests also show that the better thermal stability and fire retardancy is obtained with the Cloisites 20A or 30B. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 190–200, 2008     

Morphology and elastic modulus of novel poly[oligo(ethylene glycol) diacrylate]‐montmorillonite nanocomposites

Novel thermosetting poly[oligo(ethylene glycol) diacrylate]‐sodium montmorillonite nanocomposites containing a range of clay volume fractions were prepared by an in situ polymerization method. X‐ray diffraction showed that the basal plane spacing of the clay was increased to approximately 1.7 nm regardless of clay volume fraction. Transmission electron microscopy confirmed the basal spacing and intercalated structure. The elastic moduli of the composites were measured using ultrasonic pulse‐echo equipment. The results show that the Young's modulus and shear modulus increase with nominal clay volume fraction up to 0.22, and are in good agreement with the well‐established Christensen method and derived Hashin–Shtrikman bounds for conventional composites provided that the true volume fraction of clay reinforcement filler is calculated. At low clay volume fractions, the composites were transparent. When the nominal clay volume fraction was further increased, cracks and porous surfaces appeared, as observed by scanning electron microscopy. These defects decreased the elastic modulus, indicating an upper limit for clay additions in this preparation route. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1785–1793, 2005     

Phase transition in polyamide‐66/montmorillonite nanocomposites on annealing

The crystalline‐phase transition in polyamide‐66/montmorillonite nanocomposites before melting was investigated by in situ X‐ray diffraction and is reported for the first time in this work. The phase‐transition temperature in the nanocomposites was 170 °C, 20 °C lower than that in polyamide‐66. The lower phase‐transition temperature of the nanocomposites could be attributed to the γ‐phase‐favorable environment caused by silicate layers. Meanwhile, the addition of silicate layers changed the crystal structure of the polyamide‐66 matrix and influenced the phase‐transition behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 63–67, 2003     

Solid‐state thermal stability and degradation of a family of poly(N‐isopropylacrylamide‐co‐hydroxymethylacrylamide) copolymers

There is widespread interest in responsive polymers that show cloud point behavior, but little attention is paid to their solid state thermal properties. To manufacture products based on such polymers, it may be necessary to subject them to high temperatures; hence, it is important to investigate their thermal behavior. In this study, we characterized a family of poly(N‐isopropylacrylamide‐co‐hydroxymethylacrylamide) copolymers. Although poly(N‐isopropylacrylamide) shows very high thermal stability (up to 360 °C), introduction of hydroxy side chains leads to a significant reduction in stability and new degradation processes become apparent. Thermogravimetric analysis and fourier transform infrared spectroscopy (FT‐IR) indicate that the first degradation process involves a chemical dehydration step (110–240 °C), supported by the nonreversing heat flow response in modulated temperature differential scanning calorimetry. Water loss scales with the fraction of hydroxy monomer in the copolymer. Glass transition temperatures (T_g) are higher than the temperatures causing dehydration; hence, these values relate to newly‐formed copolymer structures produced by controlled heating under nitrogen. Fourier transform‐Raman (FT‐Raman) spectra suggest that this transition involves imine formation. The T_g increases as the fraction of hydroxy groups in the original copolymer increases. Further heating leads to degradation and mass loss, and more complex changes in the FT‐IR spectra, consistent with formation of unsaturated species. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010