Melt intercalation of polystyrene in layered silicates

We have studied the melt intercalation of polystyrene into organically modified sodium bentonite, a layered, mica-type silicate, using a variety of techniques. Wide-angle X-ray scattering experiments on polymer/silicate hybrid samples demonstrate that intercalation of polymer chains leads to an ∼25% increase in the spacing between silicate layers. The magnitude of this increase, compared with the radius of gyration of the melt polymer, implies a flattened conformation of chains in the galleries. Low voltage scanning electron microscopy reveals voids in the intercalated hybrid matrix that correspond to regions where pristine polymer was present in the physical mixture of polymer and silicate before intercalation. Differential scanning calorimetry shows that only unintercalated polymer contributes to the measured glass transition trace, so that the magnitude of the trace is diminished upon intercalation. © 1996 John Wiley & Sons, Inc.     

Nanocomposites of NLO chromophore‐modified layered silicates and polypropylene

Intercalation of guest species into layered inorganic solids is a method of producing ordered inorganic–organic assemblies with unique microstructures controlled by host–guest and guest–guest interactions. Smectite clay minerals, such as montmorillonite, having appropriate functional molecules in between the silicate layers are supposed to exhibit a wide range of novel characteristics. Nanocomposite material based on maleic anhydride‐grafted polypropylene and dye‐modified layered silicate was developed. Characteristics of organo‐modified montmorillonite particles and polymer/clay hybrids have been investigated through FTIR, SAXS, DSC, UV measurements, and transmission electron microscopy. The results of the intercalation process, structural characterization, and thermal properties will be discussed in comparison with the intercalation and nanocomposite preparation results. The intercalation was successfully conducted by the ion‐exchange method. It was shown that intercalated dibenzilidene acetone type chromophores exist in the clay galleries in an aggregated form, probably as J‐aggregates. This feature strongly effects on optical and nonlinear optical properties of nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2493–2502, 2005     

壳聚糖基层状硅酸盐纳米复合材料

壳聚糖基层状硅酸盐纳米复合材料是采用简单的溶液插层法,将壳聚糖及其衍生物插层进入层状硅酸盐的纳米层间而获得的有机无机纳米杂化材料。该材料偶合了壳聚糖及其衍生物和层状硅酸盐的协同优势,为壳聚糖的研发应用开辟了新方向和新途径。本文在对壳聚糖和层状硅酸盐的特性及应用进行简单介绍的基础上,重点综述了壳聚糖基层状硅酸盐纳米复合材料的制备方法、插层机理及应用现状,并提出了目前存在的主要问题。     

Rheological properties of diblock copolymer/layered‐silicate nanocomposites

The melt‐state viscoelastic properties of nanocomposites prepared with a symmetrical polystyrene–polyisoprene block copolymer and organically modified layered silicates are examined. Nanocomposites based on three thermodynamically equivalent organically modified layered silicates, primarily differing in lateral disk diameter (d), are studied with small‐amplitude oscillatory shear. The effects of the domain structure of the ordered block copolymer and the mesoscale dispersion of the layered silicates on the rheological properties are examined via a comparison of data for the nanocomposites in the ordered and disordered states of the block copolymer. Hybrids prepared with 5 wt % organically modified fluorohectorite (d ～ 10 μm) and montmorillonite (d ～ 1 μm) demonstrate a notable decrease in the frequency dependence of the moduli at low frequencies and a significant enhancement in the complex viscosity at low frequencies in the disordered state. This behavior is understood in terms of the development of a percolated layered‐silicate network structure. However, the viscoelastic properties in the disordered state with 5 wt % organically modified laponite (d ～ 30 nm) and in the ordered state of the block copolymer for all layered silicates demonstrate only minor changes from those observed for the unfilled polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1434–1443, 2002     

Properties of covalently bonded layered‐silicate/polystyrene nanocomposites synthesized via atom transfer radical polymerization

Covalently bonded layered silicated/polystyrene nanocomposites were synthesized via atom transfer radical polymerization in the presence of initiator‐modified layered silicate. The resulting nanocomposites had an intercalated and partially exfoliated structure, as confirmed by X‐ray diffraction and transmission electron microscopy. The thermal properties of the nanocomposites improved substantially over those of neat polystyrene. In particular, a maximum increase of 35.5 °C in the degradation temperature was displayed by these nanocomposites. Additionally, the surface elastic modulus and hardness of these nanocomposites were more than double those of pure polystyrene. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 534–542, 2005     

Nanomorphology and fire behavior of polystyrene/organoclay nanocomposites containing brominated epoxy and antimony oxide

Organoclay nanocomposites were prepared by ultrasound‐assisted solution intercalation technique based on polystyrene containing brominated epoxy and a combination of brominated epoxy and antimony oxide. Aspects of nanomorphology and nanodispersion were investigated by X‐ray diffraction and transmission electron microscopy whereas flammability and reaction to fire were evaluated using limiting oxygen index, UL‐94, and mass loss calorimeter tests. Polystyrene/brominated‐epoxy‐blend‐based nanocomposites showed mixed intercalated–exfoliated nanomorphology where polymer‐intercalated crystallites predominantly exist in polystyrene matrix and exfoliated silicate layers reside on polystyrene/brominated epoxy phase boundaries and within brominated epoxy domains. Organoclay was found to impart a compatibilization effect on polystyrene and dispersed brominated epoxy, which facilitates uniform distribution of a fine flame‐retarding phase within the matrix. With the reduction of the rate at which decomposition products evolve into the gas phase, organoclay nanocomposites showed notable reductions in peak heat release rate and increases in limiting oxygen index. The gas‐phase hot radical entrapment by halogenated flame‐retardant system was coupled with the condensed‐phase physical action of nanodispersed organoclay, which increased the overall fire‐retardant effectiveness. Fire‐retardant mechanisms of nanocomposites based on polystyrene/brominated epoxy blends were attributed to nanoconfinement and tortuous pathway effects of organoclay rather than to carbonaceous char formation proposed earlier for polystyrene/organoclay systems without conventional flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.     

Polyethylene/Clay Nanocomposite by In‐Situ Exfoliation of Montmorillonite During Ziegler‐Natta Polymerization of Ethylene

Complete exfoliation of montmorillonite during Ti‐based Ziegler‐Natta polymerization of ethylene has been successfully carried out by using montmorillonite (MMT‐OH) modified with intercalation agents containing hydroxyl groups. Hydroxyl groups in intercalation agents offer facile reactive sites for anchoring catalysts in between silicate layers. Comparison of exfoliation characteristics between MMT‐OH and non‐intercalated montmorillonite showed that the feasibility of exfoliation during ethylene polymerization was highly dependent on the catalyst fixation method.     

Morphology and rheology of polystyrene nanocomposites based upon organoclay

A correlation between morphology development and rheology of polystyrene nanocomposites based upon organophilic layered silicates (organoclay) such as fluoromicas was found as a function of the silicate modification. Organoclay was obtained by means of ion exchange of clay with protonated amine‐terminated polystyrenes with molar mass of M_n = 121 and 5 800 g/mol. Only when applying shear forces during melt compounding of organoclay modified with high molar mass polystyrene (PS), individual silicate platelets of 1 nm diameter and 600 nm length were obtained. Dispersions of such in‐situ formed nanoparticles with aspect ratio of 600 accounted for unique elastic properties observed in the low frequency range of the dynamic modulus, whereas organoclay modified with low molecular PS did not exfoliate and exhibited rheological behavior very similar to that of conventional fillers.     

Polymorphic behavior in syndiotactic polystyrene/clay nanocomposites

X‐ray diffraction methods were used in an investigation of the structural changes in syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay was prepared by the intercalation of sPS polymer into layered montmorillonite. Both X‐ray diffraction data and transmission electron microscopy micrographs of sPS/clay nanocomposites indicated that most of the swellable silicate layers were exfoliated and randomly dispersed in the sPS matrix. The X‐ray diffraction data also showed the presence of polymorphism in the sPS/clay nanocomposites. This polymorphic behavior was strongly dependent on the thermal history of the sPS/clay nanocomposites from the melt and on the content of clay in the sPS/clay nanocomposites. Quenching from the melt induced crystallization into the α‐crystalline form, and the addition of montmorillonite probably increased heterophase nucleation of the α‐crystalline form. The effect of the melt crystallization of sPS and sPS/clay nanocomposites at different temperatures on the crystalline phases was also examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 736–746, 2002     

Investigation of the effects of silicate modification on polymer‐layered silicate nanocomposite morphology

The morphological behavior of a series of polymer‐layered silicate nanocomposites (PLSNs) has been investigated. The goal was to probe the effect of “textured” silicate surfaces on PLSN morphology. The nanocomposites were fabricated by mixing montmorillonite clay that was carefully modified with tailor‐made polystyrene (PS) surfactants into a PS homopolymer matrix, where the chemical similarity of the matrix polymer and surfactants assures complete miscibility of surfactant and homopolymer. To examine the effect of silicate surface “texture,” clay was modified with combinations of long and short surfactants. The samples were then direct melt annealed to allow the equilibrium morphology to develop, and characterized by small‐angle X‐ray scattering. Based on the implications of the Balazs model and other work on the wetting behavior of polymer melts with longer surfactants and textured surfaces we expected that the intercalation of the homopolymer matrix material into the modified clay would be promoted. Extensive characterization of both the modified clays as well as the resultant nanocomposites clearly show that the modified clays exhibit a high degree of order, but also that only phase‐separated morphologies are formed in the corresponding nanocomposites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4075–4083, 2004     

聚丙烯/层状硅酸盐纳米复合材料的制备、结构和性能

聚丙烯／层状硅酸盐纳米复合材料可通过丙烯单体插层聚合、聚丙烯溶液插层和聚丙烯熔融插层等方法制备，得到插层型或剥离型纳米复合材料，形成了与传统填充型聚合物复合材料不同的微观结构，其机械性能，热性能，阻隔性能和流变性能等明显提高，由于聚丙烯的非极性及层状硅酸盐纳米复合材料制备方法的特殊性，该研究具有一定的理论价值。     

Intercalation of poly(oxyethylene) alkyl ether into a layered silicate kanemite

Poly(oxyethylene) alkyl ether (CnEOm) is intercalated into the interlayer space of a layered silicate kanemite by using layered hexadecyltrimethylammonium (C16TMA) intercalated kanemite (C16TMA-kanemite) as the intermediate. C16TMA-kanemite was treated with an aqueous solution of C16EO10, and the intercalation of C16EO10 was confirmed by the slight increase in the basal spacing (from 2.92 to 3.34 nm) with the increase in the carbon content, yielding C16EO10-C16TMA-kanemite. The product was dispersed again in a C16EO10 aqueous solution, and then 1.0 M HCl was added to the suspension to remove C16TMA ions completely. The basal spacing was further increased (from 3.34 to 5.52 nm) and the content of nitrogen was virtually zero, indicating further intercalation of C16EO10 molecules and complete elimination of C16TMA ions simultaneously. Though C16EO10 molecules are not directly intercalated into kanemite, the mutual interactions among C16TMA ions, C16EO10 molecules, and the interlayer silicate surfaces effectively induce the intercalation of C16EO10. C16EO10-kanemite shows a reversible adsorption of n-decane and water owing to the hydrophobicity and hydrophilicity of C16EO10, respectively, in the interlayer space. Layered CnEO10-kanemites (n = 12 and 18) were also synthesized in a manner similar to layered C16EO10-kanemite.     

Deintercalation of a chemically switchable polymer from a layered silicate nanocomposite

The phenomenon of intercalation is widely known as a key process in the area of polymer/layered silicate nanocomposites. In the formation of such nanocomposites, a polymer chain is intercalated between the layers of a layered (silicate) host, typically giving a well-ordered multilayered stack with a repeat distance of only a few nanometers. Intercalated systems are excellent models for studies of confined geometries, and they often display enhanced material properties as well. In this study, we examined a series of polymers in which it was possible to reverse the intercalation process (i.e., to achieve deintercalation). Homopolymers and copolymers of poly(methyl methacrylate) and poly(tetrahydropyranyl methacrylate) (PTHPMA) were intercalated into an organically modified synthetic fluoromica. Thermally induced deprotection of the tetrahydropyranyl group resulted in the transformation of PTHPMA into poly(methacrylic acid), which was then observed to deintercalate from the silicate host. X-ray diffraction and thermogravimetric analysis were used to study the deintercalation process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3151–3159, 2003     

Synthesis and Rheology of Intercalated Polystyrene/Na+‐Montmorillonite Nanocomposites

Polystyrene (PS)/clay nanocomposites were synthesized by the emulsion polymerization of styrene in the presence of sodium ion‐exchanged montmorillonite (Na⁺‐MMT), demonstrating that the strongly hydrophobic PS was intercalated into the hydrophilic silicate layers. The nanocomposites were examined by means of X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis. The rheological properties of the PS/Na⁺‐MMT nanocomposites were also studied to exhibit more pronounced shear thinning behavior with increasing clay content.     

Biopolymer-layered polysilicate micro/nanocomposite based on chitosan intercalated in magadiite

On the basis of their high adsorption and cation exchange capacity, swelling potential and low toxicity, layered sodium silicate magadiite (Na–magadiite) is an attractive solid for intercalation of polymers. This study envisages the intercalation of cationic biopolymer chitosan (Chit) in Na–magadiite to prepare a Chit/magadiite micro/nanocomposite. Characterisation of starting-magadiite, pure chitosan and Chit/magadiite were investigated using powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and thermal analysis. XRD confirmed that the chitosan had been intercalated into the interlayer space of magadiite by increasing the basal spacing, d₀₀₁ from 15.6 Å to 21.45 Å. The presence of characteristic bands of biopolymer and layered silicate in Chit/magadiite were confirmed by FTIR analysis. The thermal stability of micro/nanocomposite was evaluated by thermogravimetry analysis. The results suggested the formation of electrostatic interactions by protonated amine groups with the negatively charged magadiite surface as well as intercalation in the form of a predominant monolayer arrangement of chitosan chains in layered silicate magadiite.     

新型纳米层状硅酸盐Magadiite主体材料的制备、表征、结构和生成机理研究

利用简单的插层反应方法成功地制备了四丁基氢氧化铵(TBAOH)插层的层状硅酸盐Magadiite纳米复合材料,在室温下该材料溶胶放置30d可以保持稳定,粉体长期保存结构稳定,而且反应时间短,只需30min.利用XRD,FTIR,SEM和HRTEM等方法对样品进行了结构表征.结果表明,TBA⁺离子在层间以双分子层排列,并与层状硅酸盐结合在一起,TBAOH插层后的纳米粒子在玻璃片上进行了重组,粒径分布在10～100nm之间;HRTEM电镜照片进一步证实了剥离的层状硅酸盐纳米粒子在玻璃片上的自组装过程.根据实验结果阐述了TBAOH插层反应形成纳米溶胶的机理.     

Surface characterization and properties of plasma‐modified cyclic olefin copolymer/layered silicate nanocomposites

In this study, cyclic olefin copolymer (COC)/layered silicate nanocomposites (CLSNs) were prepared by the intercalation of COC polymer into organically‐modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of CLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the COC matrix. The effect of layered silicate on the mechanical and barrier properties of the fabricated nanocomposites shows significant improvements in the storage modulus and water permeability when compared with that of neat COC matrix. Surfaces of COC and CLSN films were modified by a mixture of oxygen (O₂) and nitrogen (N₂) plasmas with various treated times, system pressures, and radio frequency (RF) powers. The surfaces of plasma‐modified COC and CLSN were investigated using scanning probe microscopy and contact‐angle measurements. The exposure of the COC and CLSN film to the plasmas led to the combination of etching reactions of polymer surface initiated by plasma and the following addition reactions of new functional groups onto polymer surfaces to change the topology of COC film surfaces. The surface roughness was closely related to how high and how long the RF power was input into the system. The plasmas also led to changes in the surface properties of the CLSN surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surface decreases. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2745–2753, 2005     

Functional copolymer/organo‐MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA‐alt‐1‐octadecene)‐g‐PLA layered silicate nanocomposites with nanoporous core–shell morphology

Novel bioengineering functional copolymer‐g‐biopolymer‐based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L‐lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1‐octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo‐MMT clay (reactive ODA‐MMT and non‐reactive DMDA‐MMT) complexes as nanofillers and tin(oct)₂ as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT‐IR spectroscopy, X‐ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA‐DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro‐ and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H‐bonding and self‐organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride‐containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer‐g‐biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Nanoalloy Based on Clays: Intercalated‐Exfoliated Layered Silicate in High Performance Elastomer

A novel method is described for the preparation of nanocomposites comprising a high performance rubber for tire application and layered silicates clay. In this work nanocomposites of solution‐styrene butadiene rubber (S‐SBR) with montmorillonite layered silicate were prepared with carboxylated nitrile rubber (XNBR), a polar rubber, as a compatibilizer. A sufficient amount of organomodified layered silicate was loaded in carboxylated nitrile rubber (XNBR) and this compound was blended as a master batch in the S‐SBR. Mixed intercalated/exfoliated morphologies in the nanocomposite are evinced by X‐ray diffraction measurements and transmission electron microscopy. Dynamic mechanical analysis also supports the compatibility of the composites. A good dispersion of the layered silicate in the S‐SBR matrix was reflected from the physical properties of the nanocomposites, especially in terms of tensile strength and high elongation properties.     

Preparation and Characterization of Poly(butyleneterephthalate)/Organoclay Nanocomposites

PBT/organic montmorillonite (MMT) nanocomposites were prepared via melt intercalation and their nanostructure was characterized by means of X‐ray diffraction and transmission electron microscopy. Nanocomposite formation requires sufficiently hydrophobic organically modified layered silicates, as well as the presence of polar interactions between silicate and polymer. Three different alkylammonium surfactants were used to modify MMT. In addition, epoxy resin was added as a third component, and the effects on the intercalation and exfoliation behavior of the PBT nanocomposites were investigated.