Microcellular processing and relaxation of poly(ether ether ketone)

The semicrystalline microcellular closed‐cell foams are prepared by a two‐stage batch foaming process from poly(ether ether ketone) and characterized by scanning electronic microscopy. It can be observed that there are two kinds of cells with obviously different cellular sizes in the same transect and the distribution of larger cells (about 7 μm) looks like sandwich. The effects of foaming temperatures and transfer times on the cellular sizes and cell densities of porous materials were discussed. Particular emphasis was given to the effects of crystalline on the microcellular morphology. The relaxation mechanism of microcellular materials was systemically investigated by dynamic mechanics analysis. A plain on the storage modulus curve before T_g was observed due to the densification of cells. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2890–2898, 2007     

Copper‐mediated radical polymerization on a microcellular monolith surface

High‐capacity microcellular monoliths were prepared by a two‐step process, including the synthesis of a bromoester‐functionalized scaffold by the copolymerization of a highly concentrated emulsion and an in situ surface polymerization of methyl methacrylate with atom transfer radical polymerization. The influence of various parameters, such as the feed ratio, the concentration of immobilized bromoester groups, and the presence of a spacer group on the poly(methyl methacrylate) loading, was studied. Monoliths with capacities of up to 7 mmol g^?1 were obtained. Thermogravimetric analyses, scanning electron microscopy experiments, and mercury intrusion porosimetry measurements were used for the characterization of the final materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1216–1226, 2004     

Preparation,characterization, and mechanical properties of microcellular poly(aryl ether ketone) foams

High‐performance microcellular closed‐cell foams were prepared by a two‐stage batch foaming process from fluorinated poly(ether ether ketone) and characterized by scanning electronic microscopy, tensile, and dynamic mechanical analysis (DMA). The effects of saturation pressure and temperature on the cell size, cell density, and bulk density of porous materials had been discussed. The resulting materials had average cell diameters in the range 3–17 μm, and cell densities (N_f) in the order of 0.6 × 10⁹–1.39 × 10¹⁰ cells/cm³. The porosity (V_f) was in the range of 0.2–0.85. In contrast, experimental values of Young's moduli were in good agreement with theoretically predicted values, but the relative strengths were somewhat lower than that predicted. The relaxation mechanism of microcellular was systematically investigated by DMA. The dynamic mechanical spectrometry showed that the storage modulus curve at high temperature region appeared a peak and the loss modulus was lower as compared to their solid counterparts. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 173–183, 2007     

Three‐dimensional structural analysis of a block copolymer by scanning electron microscopy combined with a focused ion beam

A three‐dimensional (3D) lamellar structure of a poly(styrene‐block‐isoprene) block copolymer was observed at submicrometer and micrometer levels by scanning electron microscopy combined with a focused ion beam (FIB–SEM). The 3D lamellar structure with an exceptionally large periodicity, about 0.1 μm, was successfully reconstructed, and the size of the reconstructed image by FIB–SEM was 6.0 × 6.0 × 4.0 μm³, which was greater than the transmission electron microtomography data, 3.8 × 3.9 × 0.24 μm³, by a factor of about 40. This result indicates that 3D reconstruction using FIB–SEM is quite useful for direct 3D observations, especially analyses of polymeric materials at the submicrometer and micrometer levels. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 677–683, 2007     

Synthesis of PS and PDMAEMA mixed polymer brushes on the surface of layered silicate and their application in pickering suspension polymerization

An ammonium free radical initiator was ion exchanged onto the surface of clay layers. Polystyrene (PS) and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) mixed polymer brushes on the surface of clay layers were prepared by in situ free radical polymerization. PS colloid particles armored by clay layers with mixed polymer brushes were prepared by Pickering suspension polymerization. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the colloid particles. Clay layers on the surface of PS colloid particles can be observed. Because of the cationic nature of the PDMAEMA brushes the colloid particles have positive zeta potentials at low pH values. X‐ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N_1s binding energy of PDMAEMA chains on the surface of clay layers was detected by XPS. The two peaks of the N_1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA chains, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5759–5769, 2007     

Amine‐cured epoxy/clay nanocomposites. I. Processing and chemical characterization

The processing of nanocomposite materials composed of amine‐cured diglycidyl ether of bisphenol A (DGEBA) reinforced with organomontmorillonite clay is reported. A novel sample preparation scheme was used to process the modified clay in the glassy epoxy network, resulting in nanocomposites where the clay was both exfoliated and intercalated by the epoxy network. The processing scheme involves sonication of the constituent materials in a solvent, followed by solvent extraction to generate a composite with homogeneous dispersions of the nanoclay. Fourier transform infrared spectroscopy (FTIR) and Fourier transform (FT‐)Raman spectroscopy confirmed that the chemical structure of the epoxy network was not affected by the use of solvents in this processing scheme. The glass‐transition temperature, T_g, linearly increased with an increased weight ratio of the nanoclay. The microstructure of clay nanoplatelets in the composites was observed with transmission electron microscopy (TEM), wide‐angle X‐ray scattering (WAXS), and small‐angle X‐ray scattering (SAXS). It was found that the clay nanoplatelets were well‐dispersed, and were intercalated as well as exfoliated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4384–4390, 2004     

Polymorphism behavior of poly(ethylene naphthalate)/clay nanocomposites

Thermally stable organically modified clays based on 1,3‐didecyl‐2‐methylimidazolium (IM2C10) and 1‐hexadecyl‐2,3‐dimethyl‐imidazolium (IMC16) were used to prepare poly(ethylene naphthalate) (PEN)/clay nanocomposites via a melt intercalation process. The clay dispersion in the resulting hybrids was studied by a combination of X‐ray diffraction, polarizing optical microscopy, and transmission electron microscopy. It was found that IMC16 provided better compatibility between the PEN matrix and the clay than IM2C10, as evidenced by some intercalation of polymer achieved in the PEN/IMC16‐MMT hybrid. The effects of clay on the crystal structure of PEN were investigated. It was found that both pristine MMT and imidazolium‐treated MMT enhanced the formation of the β‐crystal phase under melt crystallization at 200 °C. At 180 °C, however, the imidazolium‐treated MMT was found to favor the α‐crystal form instead. The difference in clay‐induced polymorphism behavior was attributed to conformational changes experienced by the clay modifiers as the crystallization temperature changes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1040–1049, 2006     

Facile green strategy for micro/nano structured conducting polyaniline‐clay nanocomposite via template polymerization using amphiphilic dopant, 3‐pentadecyl phenol 4‐sulphonic acid

Novel self‐assembled nano/microstructured conducting PANICN was prepared by in situ intercalative emulsion polymerization of aniline in aqueous dispersion of clay using bifunctional amphiphilic dopant, 3‐pentadecyl phenol‐4‐sulphonic acid (PDPSA) derivable from renewable resource. X‐ray diffraction and scanning electron microscopy (SEM) studies revealed the formation of monolayer of protonated PANI intercalated nanoclays with template polymerized self‐assembled micro/nanostructured protonated PANI. Nano/micro structured PANIs were formed by the supra molecular self‐assembling of the inter‐chain hydrogen bonding, inter‐plane phenyl stacking and electrostatic layer by layer self‐assembling (ELBS) between polarized alkyl chains present dopant anions and were manifested using fourier transform infra red spectroscopy and differential scanning calorimetry. On the basis of the results, structure‐directing effect of ‘anilinium salt micelle’ was schematically illustrated in this article. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2664–2673, 2007     

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     

Electrical conductivity and polarization processes in nanocomposites based on isotactic polypropylene and modified synthetic clay

The direct‐current and alternating‐current electrical behavior of nanocomposites, formed by isotactic polypropylene partially modified with maleic anhydride and filled with different amounts of modified synthetic clay, has been studied; moreover, the conduction mechanisms and the relaxation processes that take place in the materials have been investigated. The nanocomposites containing small clay contents exhibit direct‐current insulating properties comparable to or even higher than those observed in the polymeric matrix. However, as the synthetic clay content increases, the ionic contribution to conductivity becomes considerable. The nanocomposites also show a slightly higher permittivity and loss factor than the host material because of the appearance of a thermally activated relaxation process in the frequency range of 10^?2 to 10² Hz at the investigated temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 705–713, 2007     

Thermal properties of polystyrene nanocomposites formed from rigid intercalation agent‐treated montmorillonite

Polystyrene (PS)/clay nanocomposites were prepared with two different new intercalation organophilic clays, the phosphonium salt (APP) and the ammonium 4‐(4‐adamantylphenoxy)‐1‐butanamine (APB) salts, by emulsion polymerization technique. X‐ray diffraction and transmission electron microscopy were performed to characterize the layered structures of APB‐ and APP‐treated polymer–clay nanocomposites, and both resulted in exfoliated structures. Molecular weights of PS obtained from these nanocomposites are slightly lower than the virgin PS formed under similar polymerization conditions. Coefficient of thermal expansion showed approximately a 44–55% decrease for APB‐ and APP‐intercalated clay nanocomposites relative to the pure PS. Both T_g and thermal decomposition temperature of the PS component in the nanocomposite are higher than the virgin PS, implying that the presence of clay is able to enhance thermal stabilities of the PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1781–1787, 2007     

Efficient photoinduced In situ preparation of clay/poly(glycidyl methacrylate) nanocomposites using hydrogen‐donor silane

Clay/poly(glycidyl methacrylate) nanocomposites (clay/PGMA) were prepared by in situ radical photopolymerization using N,N‐dimethylaminopropyltrimethoxysilane(DMA)‐modified bentonite clay acting as hydrogen donor for benzophenone in solution. This initiating system permits to photopolymerize glycidyl methacrylate between the lamellae of the DMA‐modified clay. The approach provides exfoliated nanocomposites as judged by the measurements of X‐ray diffraction. However, a low fraction of persistent intercalated clay regions was visible by transmission electron microscopy. X‐ray photoelectron spectra analyses indicate that the nanocomposites have PGMA‐rich surface. The clay/PGMA nanocomposites can be readily dispersed in ethanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 800–808     

Mechanical properties of polymer‐blend nanocomposites with organoclays: Polystyrene/ABS and high impact polystyrene/ABS

Thirty‐three polystyrene (PS)/acrylonitrile‐butadiene‐styrene (ABS) and high impact PS/ABS polymer blends with organoclay and copolymer additives were prepared by melt processing using different mixing sequences in order to test the putative capability of clay to perform a compatibilizing role in polymer blends. In general, the addition of clay increased the tensile modulus and had little effect on tensile strength. For the blends studied in this work, the addition of organoclays caused a catastrophic reduction in impact strength, a critical property for commercial viability. The polymer‐blend nanocomposites adopted a structure similar to that for ABS/clay nanocomposites as determined by X‐ray diffraction and transmission electron microscopy. It is suggested that clay reinforcement inhibits energy absorption by craze formation and shear yielding at high strain rates. Simultaneous mixing of the three components provided nanocomposites with superior elongation and energy to failure compared to sequential mixing. The clay pre‐treated with a benzyl‐containing surfactant gave the best overall properties among the various organoclays tested and of the two clay contents studied 4 wt % was preferred over 8 wt % addition. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Effects of spacing between the exfoliated clay platelets on the crystallization behavior of polyamide‐6 in polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organoclay nanocomposite films with planar‐oriented clay platelets were prepared by the simple hot pressing of melt‐extruded nanocomposite pellets. The average distance between the neighboring clay platelets was controlled by changes in the clay loading content in the nanocomposites. The effects of the clay platelet spacing on the crystallization behavior of PA6 were investigated with transmission electron microscopy and wide‐angle X‐ray diffraction. The crystal lamellae were found to be mainly perpendicular to the clay surface for the nanocomposites with large spacing between the clay sheets at low clay loading contents. This perpendicular orientation morphology was attributed to the strong interactions between the PA6 molecular chain and the clay surface. In contrast, the crystal lamellae were found to be parallel to the clay surface when the spacing between the neighboring clay platelets was less than 30 nm. It was concluded that the confinement crystallization of PA6 within the nanoscale channels formed by clay sheets resulted in this parallel orientation texture. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 284–290, 2006     

Influence of organic modifiers on morphology and crystallization of poly(ϵ‐caprolactone)/synthetic clay intercalated nanocomposites

ε‐caprolactone was polymerized in the presence of neat montmorillonite or organomontmorillonites to obtain a variety of poly(ε‐caprolactone) (PCL)‐based systems loaded with 10 wt % of the silicates. The materials were thoroughly investigated by different X‐ray scattering techniques to determine factors affecting structure of the systems. For one of the nanocomposites it was found that varying the temperature in the range corresponding to crystallization of PCL causes reversible changes in the interlayer distance of the organoclay. Extensive experimental and literature studies on this phenomenon provided clues indicating that this effect might be a result of two‐dimensional ordering of PCL chains inside the galleries of the silicate. Small angle X‐ray scattering and wide angle X‐ray scattering investigation of filaments oriented above melting point of PCL revealed that polymer lamellae were oriented perpendicularly to particles of unmodified silicate, while in PCL/organoclay systems they were found parallel to clay tactoids. Calorimetric and microscopic studies shown that clay particles are effective nucleating agents. In the nanocomposites, PCL crystallized 20‐fold faster than in the neat polymer. The crystallization rate in nanocomposites was also significantly higher than in microcomposite. Further research provided an insight how the presence of the filler affects crystalline fraction and spherulitic structure of the polymer matrix in the investigated systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2350–2367, 2007     

PS/PMMA mixed polymer brushes on the surface of clay layers: Preparation and application in polymer blends

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X‐ray diffraction, and high‐resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo‐PMMA chains and PMMA brushes on the surface of clay layers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329–5338, 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     

Effects of clay‐modifying agents on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites synthesized via γ‐ray irradiation polymerization

Via γ‐ray irradiation polymerization, poly(methyl methacrylate) (PMMA)/clay nanocomposites were successfully prepared with reactive modified clay and nonreactive clay. With reactive modified clay, exfoliated PMMA/clay nanocomposites were obtained, and with nonreactive clay, intercalated PMMA/clay nanocomposites were obtained. Both results were confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. PMMA extracted from PMMA/clay nanocomposites synthesized by γ‐ray irradiation had higher molecular weights and narrow molecular weight distributions. The enhanced thermal properties of the PMMA/clay nanocomposites were characterized by thermogravimetric analysis and differential scanning calorimetry. The improved mechanical properties of PMMA/clay were characterized by dynamic mechanical analysis. In particular, the enhancement of the thermal properties of the PMMA/clay nanocomposites with reactive modified clay was much more obvious than that of the PMMA/clay nanocomposites with nonreactive clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3218–3226, 2003     

Effect of flocculated structure on rheology of poly(butylene terephthalate)/clay nanocomposites

The microstructure and rheological property of poly(butylene terephthalate) (PBT)/epoxy/montmorillonite nanocomposites (PCNs) were investigated. For the study, PCNs were prepared by melt intercalation in clay content of 4 wt % and, epoxy loadings were varied from 2 to 4 wt %. The intercalated PCNs are characterized by different techniques such as transmission electron microscopy, Fourier transform infrared and rheology. It is interesting that the percolated tactoids network in the ternary hybrids becomes insensitive to the shear deformation with the addition of epoxy in contrast to that in the sample without epoxy, which can be attributed to the formation of a flocculated structure of clay tactoids because of the chain‐extension reactions between PBT matrix and epoxy and possible hydrogen bonding. The flocculated structure has influence on the rheological behavior of the hybrids remarkably, strengthening the percolated strong‐associated‐tactoids network and reducing the percolation threshold, while not changing the strain‐scaling. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2807–2818, 2005     

Poly(cyclohexene oxide)/clay nanocomposites by photoinitiated cationic polymerization via activated monomer mechanism

Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X‐ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328–5335, 2009