Assessing organo‐clay dispersion in polymer nanocomposites

Organo‐clay polymer nanocomposites offer improved material properties at very low filler loadings making them of immediate interest for application in body panels, claddings, and instrument panels. This improvement in properties requires that the organo‐clay be well dispersed if not completely exfoliated. Conventionally, the dispersion and exfoliation of the organo‐clay is evaluated using transmission electron microscopy (TEM) and X‐ray diffraction (XRD). Although both TEM and XRD data were found to correlate with flexural modulus of thermoplastic olefin nanocomposite materials, only TEM proved successful in quantifying the dispersion of the organo‐clay in all nanocomposite materials (exfoliated, tactoid, or agglomerated tactoid). XRD was found to be capable of detecting exfoliation and intercalation but is limited because of clay dilution, preferred orientation, mixed‐layering, and other peak broadening factors. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1110–1117, 2004     

Self‐assembled polymer nanocomposites and their networks

Synthetic modifications to block‐copolymer structure‐directing agents lead to polymerizable macromers suitable for templating the growth of mesoporous silica particles, which can subsequently react in situ to form extended nanocomposites and nanocomposite networks. Suitably functionalized triblock polymers can preserve the structure‐directing capabilities of the triblock polymer for templating ordered mesoporous silica particle growth and also generate a reactive matrix for subsequent polymer network formation via the reactive end groups. The final self‐assembled products are polymer nanocomposites or novel crosslinked nanocomposite networks whose organic/inorganic composition ratios can vary systematically. The novel self‐assembly route described here should be generally applicable to the synthesis of intimately mixed nanocomposites and nanocomposite networks, starting from a wide variety of block polymeric template/macromer/ordered silica systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41111.     

Temperature‐, pH‐, and ion‐stimulus‐responsive swelling behaviors of poly(dimethylaminoethyl methacrylate) gel containing cholic acid

Poly(dimethylaminoethyl methacrylate) hydrogels containing cholic acid (PDMAEMA–CA) were synthesized by radiation crosslinking. The introduction of 10 and 20 mol% cholic acid (CA) into the poly(dimethylaminoethyl methacrylate) (PDMAEMA) hydrogel decreased the maximum swelling ratio (SR) of the gel from 40 to 6 and 5, respectively. The incorporation of CA with dimethylaminoethyl methacrylate led to a decrease in the lower critical swelling temperature of the gel from 44 to 42°C but did not exert big influence on the ion‐stimulus‐responsive properties of the gel. However, the pH sensitivity of the PDMAEMA–CA gel was quite different from that of PDMAEMA gel. The SR of PDMAEMA gel decreased at pH 2.5, whereas the SRs of the PDMAEMA–CA gels showed a convex‐upward function of pH; that is, SR of the PDMAEMA–10% CA gel first increased (pH 1.2–3.2) and then decreased (pH 3.2–11.9) with increasing pH. The pH‐stimulus‐responsive swelling behavior of the PDMAEMA–20% CA gel was similar to that of the PDMAEMA–10% CA gel except for the unique swelling behavior exhibited in the lower pH region. The unique decrease in SR in strong acidic solutions was attributed to aggregations driven by the hydrophobic interactions between CA molecules. Phase separation of the gel in strongly acidic solutions was observed; that is, the margin of the swollen gel was transparent and elastic (cellular structure), whereas the core of it was opaque (aggregated structure) as recorded by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39998.     

Durability of glass‐fiber‐reinforced polymer nanocomposites in an alkaline environment

This study was conducted to determine the effect of clay content in GFRP (glass‐fiber‐reinforced polymer) composite samples as they were aged in an alkaline solution. Two kinds of GFRP composite samples were prepared. One was E‐glass‐fiber‐reinforced vinyl ester polymer, and the other was nano‐GFRP composites prepared with the addition of 1 and 2 wt% of montmorillonite clay to the polymer matrix. These samples were aged in alkaline solution of pH 13.2 with and without sustained load. The load was 1335 N or 18.7% of the tensile strength of the composite samples. The aging was evaluated by measuring the reduction in tensile strength after 6 months. Also, absorption of alkaline solution into the plain and nano‐GFRP samples was investigated so as to elucidate the diffusion behaviors. It was found that for a short exposure time (e.g. 1 month) and without sustained load, dispersing 2 wt% of the nanoclay in the polymer matrix of the GFRP samples reduces the diffusivity by 39%. However, with the application of sustained load, the glass fiber composite samples deteriorate more with increasing clay content. The reduction in tensile strength was 7.1%, 12.1%, and 18.1% for the samples containing 0, 1, and 2 wt% of clay, respectively. J. VINYL. ADDIT. TECHNOL., 12:25–32, 2006. © 2006 Society of Plastics Engineers     

Carbon nanotubes‐polymer nanocomposites for controlled heating materials

Nanocomposites of modified carbon nanotubes (CNT) and either polyurethane (PU), poly(vinyl acetate) (PVAc), or silicone materials were synthetized and characterized for thermal mat application. The obtained results revealed that the polymer used as a matrix had an impact on the electrical resistance of the mats. The lowest results of 32 Ω of resistance was registered with silicone‐based mats containing 5 wt % of CNT. For the same CNT content the mats based on PVAc and PU displayed values of 55 and 60 Ω, respectively. The low resistance properties of silicone‐based materials were due principally to the good compatibility of both polymer and functionalized CNT. Because of the low resistance values, this mat was subjected to thermovision analysis revealing that the samples reached temperature of about 60 °C in 9 min and 70 °C after 27 min of 27 V of applied potential. The results showed an almost uniform temperature distribution in the samples’ surface with some high and low temperature spots, which were attributed to nonuniform distribution of CNT in the polymer matrix. In summary, all the obtained results confirm that silicone‐CNT are very promising materials that can be used as low‐voltage heating mats. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44194.     

Processability studies of silica‐thermoset polymer matrix nanocomposites

The aim of this study is to investigate the processability of silica‐thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5% silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent‐free and solvent‐containing systems. It was found that the best dispersion route involved a solvent‐aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

Water‐based amorphous carbon nanotubes filled polymer nanocomposites

A novel method of making water‐based amorphous carbon nanotubes (ACNTs) for advanced polymer nanocomposites is presented. In this approach, sodium dodecyl sulfate (SDS) is introduced onto the amorphous carbon nanotubes to improve the solubility in water and the dispersion in polyvinyl alcohol [PVA] matrix. As a result, the addition of 0.6 wt % ACNTs in the polymer resulted in the significant improvement (167.5 and 175.8%) in the tensile strength and modulus of the polymer, respectively. The improved mechanical property could be ascribed to the load transfer to the nanotubes in the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Near‐infrared activation of semi‐crystalline shape memory polymer nanocomposites

Recently, indirect activation of the shape memory effect has become an increasingly popular triggering modality for shape memory polymer biomaterials. Amongst the known methods for remote activation, near‐infrared radiation (NIR) remains relatively unexplored, specifically for semicrystalline materials, which possess sharp thermal transitions. Herein, poly(ε‐caprolactone) (PCL) networks were photo‐polymerized from branched precursors doped with 150 nm surface modified gold nanoshells with a surface plasmon resonance of approximately 800 nm. The effect of nanoparticle loading on the thermal, mechanical, and shape memory properties of the PCL matrix were examined. The PCL nanocomposites exhibited excellent shape fixation and nearly quantitative shape memory recovery in response to low intensity NIR irradiation. Further, the heat dissipated by the irradiated nanocomposites to the surrounding medium was found to reach a maximum at biologically relevant temperatures. As such, this nanocomposite system represents a highly attractive candidate for many biomedical shape memory applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4551–4557, 2013     

The adsorption behaviors of the multiple stimulus‐responsive poly(ethylene glycol)‐based hydrogels for removal of RhB dye

In this article, the multiple stimulus‐responsive organic/inorganic hybrid hydrogels by combining poly(2‐(2‐methoxyethoxy) ethyl methacrylate‐co‐oligo (ethylene glycol) methacrylate‐co‐acrylic acid) (PMOA) hydrogel with magnetic attapulgite/Fe₃O₄ (AT‐Fe₃O₄) nanoparticles were applied to the removal of Rhodamine B (RhB) dye from wastewater. The adsorption of RhB by the hydrogels was carried out under different external environmental, such as pH, temperature and magnetic‐field. The results showed that the hydrogels still possessed temperature, pH and magnetic‐field sensitivity during the adsorption process, which indicated that the adsorption could be controlled by the hydrogels responsive. The dye adsorption had a significant increment at 30°C and the removal of RhB could reach to over 95%. Besides, the low pH values were also favorable for the RhB adsorption, the removal was over 90% at pH = 4.56. Kinetic studies showed that the pseudo‐second order kinetic model well fitted the experimental data. The rate constant of adsorption was 0.0379 g/mg min. Langmuir and Freundlich isotherm models were applied to the equilibrium adsorption for describing the interaction between sorbent and adsorbate. The maximum K_L and K_F were 2.23 (L/g) and 0.87 (mg/g) at 30°C, respectively. Under the external magnetic‐field, the adsorption rate significantly increased within 250 min and the hydrogels could be separated easily from wastewater. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42244.     

Magnetic and electric responsive hydrogel–magnetic nanocomposites for drug‐delivery application

Magnetic and electrically responsive hydrogel networks were developed for drug‐delivery applications. The hydrogel matrices were synthesized by the polymerization of acrylamide monomer in the presence of carboxymethylcellulose (CMC) or methylcellulose (MC) with N,N‐methylenebisacrylamide, a crosslinker with the redox initiating system ammonium persulfate/tetramethylethylenediamine. The magnetic nanoparticles were generated throughout these hydrogel matrices by an in situ method by the incorporation of iron ions and their subsequent reduction with ammonia. A series of hydrogel–magnetic nanocomposites (HGMNCs) were developed with various CMC and MC compositions. The synthesized HGMNCs were characterized with spectral (Fourier transform infrared and ultraviolet–visible spectroscopy), X‐ray diffraction, thermal, and microscopy methods. These HGMNCs contained iron oxide (Fe₃O₄) nanoparticles with an average particle size of about 22 nm, as observed by transmission electron microscopy. The dielectrical properties of the pure hydrogel (HG); the hydrogel loaded with iron ions, or the hydrogel iron‐ion composite (HGIC); and the HGMNCs were measured. These results suggest that HGMNCs exhibited higher dielectric constants compared to HG and HGICs. The curcumin loading and release characteristics were also measured for HG, HGIC, and HGMNC systems. These data revealed that there was a sustained release of curcumin from HGMNCs because of the presence of magnetic nanoparticles in the hydrogel networks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Intra‐ and extra‐gallery reactions in tri‐functional epoxy polymer layered silicate nanocomposites

Achieving a high degree of exfoliation in epoxy‐based polymer layered silicate (PLS) nanocomposites is crucial to their successful industrial application, but has hitherto proved elusive. In this work, a system is presented which shows significant promise in this respect. The isothermal cure of PLS nanocomposites based upon a tri‐functional epoxy resin (TGAP) has been studied by DSC, and displays two exothermic peaks. The first peak, very rapid, relates to a homopolymerization reaction within the intra‐gallery regions, while the second peak reflects the bulk crosslinking reaction. The occurrence of the intra‐gallery reaction before the bulk reaction enhances the degree of exfoliation in the cured nanocomposite. Furthermore, pre‐conditioning the resin/clay mixture before adding the curing agent and effecting the isothermal cure also allows a greater extent of intra‐gallery reaction to occur before the extra‐gallery epoxy‐amine reaction. Consequently, this system results in a high degree of exfoliation, as revealed by transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graphene oxide reinforced chitosan/polyvinylpyrrolidone polymer bio‐nanocomposites

Bio‐nanocomposite films based on chitosan/polyvinylpyrrolidone (CS/PVP) and graphene oxide (GO) were processed using the casting/evaporation technique. It has been found that the three components of bio‐nanocomposites can be easily mixed in controlled conditions enabling the formation of thick films with high quality, smooth surface and good flexibility. Structural and morphological characterizations showed that the GO sheets are well dispersed in the CS/PVP blend forming strong interfacial interactions that provide an enhanced load transfer between polymer chains and GO sheets thus improving their properties. It has been found that the water resistance of the CS/PVP blend is improved, and the hydrolytic degradation is limited by addition of 0.75 and 2 wt % GO. The modulus, strength, elongation and toughness of the bio‐nanocomposites are together increased. Herein, the steps to form new bio‐nanocomposite films have been described, taking the advantage of the combination of CS, PVP and GO to design the aforementioned bio‐nanocomposite films, which allow to have extraordinary properties that would have promising applications as eventual packaging materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41042.     

From carbon nanotube coatings to high‐performance polymer nanocomposites

Since their discovery at the beginning of the 1990s, carbon nanotubes (CNTs) have been the focus of considerable research by both academia and industry due to their remarkable and unique electronic and mechanical properties. Among numerous potential applications of CNTs, their use as reinforcing materials for polymers has recently received considerable attention since their exceptional mechanical properties, combined with their low density, offer tremendous opportunities for the development of fundamentally new material systems. However, the key challenge remains to reach a high level of nanoparticle dissociation (i.e. to break down the cohesion of aggregated CNTs) as well as a fine dispersion upon melt blending within the selected matrices. Therefore, this contribution aims at reviewing the exceptional efficiency of CNT coating by a thin layer of polymer as obtained by an in situ polymerization process catalysed directly from the nanofiller surface, known as the ‘polymerization‐filling technique’. This process allows for complete destructuring of the native filler aggregates. Interestingly enough, such surface‐coated carbon nanotubes can be added as ‘masterbatch’ in commercial polymeric matrices leading to the production of polymer nanocomposites displaying much better thermomechanical, flame retardant and electrical conductive properties even at very low filler loading. Copyright © 2007 Society of Chemical Industry     

UV‐assisted three‐dimensional printing of polymer nanocomposites based on inorganic fillers

In this work, nanocomposites based on a UV‐curable polymeric resin and different inorganic fillers were developed for use in UV‐assisted three‐dimensional (UV‐3D) printing. This technology consists in the additive multilayer deposition of a UV‐curable resin for the fabrication of 3D macro structures and microstructures of arbitrary shapes. A systematic investigation on the effect of filler concentration on the rheological properties of the polymer‐based nanocomposites was performed. In particular, the rheological characterization of these nanocomposites allowed to identify the optimal printability parameters for these systems based on the shear rate of the materials at the extrusion nozzle. In addition, photocalorimetric measurements were used to assess the effect of the presence of the inorganic fillers on the thermodynamics and kinetics of the photocuring process of the resins. By direct deposition of homogeneous solvent‐free nanocomposite dispersions of different fillers in a UV‐curable polymeric resin, the effect of UV‐3D printing direction, fill density, and fill pattern on the mechanical properties of UV‐3D printed specimens was investigated by means of uniaxial tensile tests. Finally, examples of 3D macroarchitectures and microarchitectures, spanning features, and planar transparent structures directly formed upon UV‐3D printing of such nanocomposite dispersions were reproducibly obtained and demonstrated, clearly highlighting the suitability of these nanocomposite formulations for advanced UV‐3D printing applications. POLYM. COMPOS., 38:1662–1670, 2017. © 2015 Society of Plastics Engineers     

Synthesis and rheological properties of nickel‐zinc ferrite polymer nanocomposites

In this work, the ferrimagnetic nickel‐zinc ferrite nanopowder was synthesized via citrate‐ethylene glycol processing, followed by the preparation of the epoxy‐based nanocomposite. The materials were characterized using X‐ray diffraction (XRD), simultaneous thermal analysis (STA), alternative gradient force magnetometer (AGFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the sample calcined at 1000°C for 1 h had the best crystallinity, and the calculated crystallite size of this sample was ～ 105 nm. The rheological properties and the magnetoviscous effect of the nanocomposites were studied by a standard rotating rheometer. The effects of the magnetic fields and shear rate with respect to time were investigated, and the results were discussed in terms of aggregates and magnetic field‐induced structures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Microemulsion route to fabrication of silver and platinum‐polymer nanocomposites

Polymethylmethacrylate (PMMA)‐platinum and PMMA‐silver nanocomposites have been produced using polymerization of W/O microemulsions. MMA monomer was used as the oil or continues phase of the microemulsion system and polymerized following formation of Pt and Ag nanoparticles in the fluid medium. The UV‐vis absorption spectra have been used to trace the growth process of the nanoparticles in the microemulsion system. Scanning electron microscopy and transmission electron microscopy (TEM) have been used to determine the morphology and particle size of the Pt and Ag particles in the synthesized nanocomposites. Image analyses of TEM micrographs confirm that the Pt and Ag particles in the synthesized nanocomposites have a narrow size distribution. Meanwhile, Fourier‐transform infrared spectroscopy was used to verify polymer‐nanoparticles interaction in nanocomposite bulk. POLYM. COMPOS., 35:2023–2028, 2014. © 2014 Society of Plastics Engineers     

Preparation of a polymer containing indole groups by RAFT polymerization and one‐phase synthesis of AuNPs‐polymer nanocomposites

A one‐phase synthesis of AuNPs‐polymer nanocomposites using HAuCl₄ as the precursor is reported in this article. A flexible polymer, poly(2‐(4‐(di(1H‐indol‐3‐yl)methyl)phenoxy) ethyl methacrylate) (PMPEM), containing indole groups on the side chain was utilized as both a reducing reagent and soft template in the system. The PMPEM‐Au nanocomposites with three different sizes of AuNPs (25–50, 2, and 5 nm) were obtained just through choosing different solvents such as toluene, tetrahydrofuran (THF), and N,N‐dimethylformamide, respectively. Nanocomposites including the size of 25–50 and 2 nm AuNPs showed strong NLO absorption and refraction behaviors. The nonlinear refractive index n₂ of PMPEM‐Au nanocomposites prepared in toluene and THF were 9.35 × 10^?11 and 1.85 × 10^?10 m²/W, third‐order susceptibility χ⁽³⁾ were 2.55 × 10^?11 and 4.26 × 10^?11 esu, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Spray‐dried microspheres as a route to clay/polymer nanocomposites

A new strategy for the preparation of well‐dispersed clays in a polymer matrix by a spray‐drying method is presented. Scanning electron microscopy and transmission electron microscopy measurements show that the spray‐drying process produces clay/polymer microspheres in which the clay is trapped in a well‐dispersed state throughout the polymer matrix. The microspheres have been successfully extruded into clay/poly(methyl methacrylate) nanocomposite bulk structures without any perturbation of the well‐dispersed clay nanostructure in the original microspheres. Transmission electron microscopy and small‐angle X‐ray scattering show that the clay particles in the extruded materials range from single platelets to simple tactoids composed of a few stacked clay platelets, indicating an excellent degree of dispersion. The results show that sprayed microspheres are very good precursors for further processing such as extrusion or melt blending with other polymers for bulk nanocomposite fabrication. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Cone calorimetric and thermogravimetric analysis evaluation of halogen‐containing polymer nanocomposites

Halogen‐containing organically modified clay nanocomposites have been prepared and it was found that the presence of bromine enhances the fire retardancy of polystyrene and polypropylene nanocomposites, compared with the virgin polymers. The nanocomposites were evaluated by X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and cone calorimetric measurements. The UL‐94 test gave a V‐0 rating for some samples while cone calorimetry gave a reduced PHRR. Both the amount and identity of the bromine‐containing compound and the mode of preparation, which controls the dispersion, have a significant effect on the results. Bromine‐containing materials, at very low loading, approximately 6% or less bromine, give excellent results when the clay loading was about 3%. Copyright © 2005 John Wiley & Sons, Ltd.     

Poly(l‐histidine)‐containing polymer bioconjugate hybrid materials as stimuli‐responsive theranostic systems

For decades, researchers have aspired to develop materials for noninvasive treatment and monitoring of pathological conditions. Various organs, tissues, subcellular compartments, and their pathophysiological states can be characterized by their pH values. pH‐dependent intracellular tumor targeting has received particular attention due to the unique acidic environment of the solid tumors created by physiological and metabolical abnormalities. Responsive nanocarriers, when exposed to these pH stimuli, respond quickly to the physicochemical changes by undergoing structural deformations, such as swelling and phase transition, which favors the drug release specifically at the diseased site. Recently, researchers have developed several new poly(L ‐histidine) (p(His))‐based pH responsive systems for sustained drug release and molecular targeting. This review focuses on the p(His)‐based pH responsive nanocarriers, which are utilized in biomedical applications such as anti‐cancer drug delivery and nucleic acid delivery. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40796.