In Situ Polymerization Research Papers (original) (raw)

The two-dimensional hybrid organic-inorganic materials Zn 2 -Cr and Zn 2 -Al-LDHs (Layered Double Hydroxides) containing 4-(1H-pyrrol-1yl)benzoate anions as the interlayer anions were synthesized by the co-precipitation method at constant pH followed by subsequent hydrothermal treatment for 72 h. The materials were characterized by PXRD, 13 C CP-MAS NMR, ESR, TGA, and TEM. The basal spacing found by the X-ray diffraction technique is coincident with the formation of bilayers of the intercalated anions. Solid-state 13 C NMR and ESR data strongly suggest the partial in situ polymerization of the 4-(1H-pyrrol-1yl)benzoate anions during coprecipitation. q

- by and +2
- •
- Materials Engineering, Physics, Condensed Matter Physics, Nuclear Magnetic Resonance

This paper is devoted to investigation of morphological and physical-mechanical properties of polyethylene (PE)/clay nanocomposites prepared via in situ polymerization method using bi-supported Ziegler-Natta catalyst. Bentonite type clay and MgCl 2 (ethoxide type) were used as the support of TiCl 4. Catalyst support and polymerization process have been done in slurry phase using Triisobutylaluminum as the cocatalyst. The microstructure of the nanocomposites was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM indicated that almost fully exfoliated PE/clay nanocomposites were produced successfully using this method. According to permeability measurements, it was found that oxygen permeability values of the nanocomposite samples prepared with in situ polymerization method were dropped more than 200% introducing only 1 wt% clay to polymeric matrix. Differential scanning calorimetry (DSC) results indicated that the crystallization temperatures of samples are significantly higher than that of virgin PE. Moderate thermal stability enhancement of in situ polymerized nanocomposites was confirmed using thermogravimetric analysis (TGA).The storage modulus, Young's modulus and tensile strength of prepared samples were increased where the toughness was declined slightly. It seems that good dispersion and exfoliation of clay during polymerization should be responsible to get more effective reinforcing properties for clay in this method comparing to melt blending method for preparation of polyethylene nanocomposites.

In order to prevent corrosion of flaky aluminium particles, flaky polyacrylic acid/aluminium composite particles were prepared using in-situ polymerization. The influences of dosage of acrylic acid, ammonium persulphate, isopropanol and water, as well as reaction temperature and reaction time, on corrosion inhibition efficiency and gloss were investigated. Maximum corrosion inhibition efficiency was 99.7% and the gloss was 88.3 Gs. Using TGA, SEM, laser particle size analysis, FTIR and XPS, polyacrylic acid was found to be coated on the surface of clear aluminium particles.

- by Ahmet Gürleme
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- Chemical Engineering, Reaction Time, In Situ Polymerization, Particle Size

Polymer/carbon nanotubes nanocomposites were fabricated by an in situ polymerization process using multi-wall carbon nanotubes (MWNT) as filler in an epoxy polymer. Effects of curing process, mixing speed, mixing time, addition of ethanol, timing of hardener addition, etc., in the fabrication process on the electrical properties of nanocomposites have been investigated. In the fabrication process, the effective formation of macroscopic conducting network in matrix is most important to enhance the electrical properties of nanocomposites. It was found that the curing temperature and the mixing conditions are key factors in the fabrication process, which influence the formation of conducting network significantly. Therefore, careful design of these factors in the fabrication process is required to achieve high electrical performances of nanocomposites. The experimental percolation threshold of the resultant nanocomposites was around 0.1 wt%. Moreover, a statistical percolation model was built up to numerically investigate the percolation threshold. The experimental electrical conductivity increases from the percolation threshold following a percolation-like power law with the identified critical exponent t as 1.75.

- by Hu Go
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- Materials Engineering, Mechanical Engineering, Aerospace Engineering, Carbon Nanotube

Dynamic mechanical spectroscopy and transmission electron microscopy were utilized to investigate the properties of composites resulting from the formation of a cross-linked inorganic network via the polymerization of tetraethoxysilane (TEOS) in situ in a poly(methyl methacrylate) (PMMA) binder. The results show that the morphology and physical properties obtained are governed by sample preparation and by the catalyst used to polymerize the TEOS ; major differences are obtained when the polymerization of TEOS is performed in different pH regimes. The morphologies which develop are consistent with the known differences in gel structures obtained during the polymerization of TEOS in acidic or basic media. When TEOS is reacted under acidic conditions at elevated temperatures, small (< 100/k) SiO 2 domains which are well dispersed in the PMMA matrix result, producing a composite material with a high plateau modulus above the Tg of PMMA which extends to at least 250°C. The time-temperaturetransformation concept, proposed by Gillham for thermosetting organic polymers, is employed to explain some of these results.

- by Jeffrey Wesson
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- Engineering, Morphology, Polymerization, Polymer

Carbon nanofiber (CNF) composites have the potential for creating inexpensive, semiconducting polymers. These composites require a homogeneous dispersion within the polymer. Many groups have focused on high shear methods such as twin screw extrusion. Although high shear methods produce a homogeneous dispersion, the aspect ratio of the nanofibers is reduced by the mechanical force. In this report, we present results for low shear composite formation via in situ polymerization of cyclic oligomeric carbonates. The composites were characterized by thermal gravimetric analysis, electrical conductivity, scanning electron microscopy and transmission electron microscopy. The composites exhibit minimal aggregation of the carbon nanofibers even at high weight percents. The polycarbonate/CNF composites exhibit an electrical conductivity percolation threshold of 6.3 wt% which is higher compared with similar CNF composites. The composites also show an increase in thermal stability of 40°C as the CNF loading increases from 0 to 9 wt%.

A series of poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) was successfully prepared by in situ polymerization. The effect of diverse process parameters and ingredients on the morphology of the microcapsules was observed by SEM, optical microscopy (OM) and digital microscopy. Different techniques for the characterization of the chemical structure and the core content were considered such as FT-IR and (1)H-NMR as well as the characterization of thermal properties by DSC. High yields of free flowing powder of spherical microcapsules were produced. The synthesized microcapsules can be incorporated into another polymeric host material. In the event the host material cracks due to excessive stress or strong impact, the microcapsules would rupture to release the DCPD, which could polymerize to repair the crack.

- by Noor Hayaty Abu Kasim
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- Composites, Self-healing, Material, Microcapsules

Different compositions of poly(1-caprolactone) (PCL) and (organo-modified) montmorillonite were prepared by melt blending or catalyzed ring opening polymerization of 1-caprolactone. Microphase composites were obtained by direct melt blending of PCL and sodium montmorillonite (MMT-Na þ ). Exfoliated nanocomposites were obtained by in situ ring opening polymerization of 1-caprolactone with an organo-modified montmorillonite (MMT-(OH) 2 ) by using dibutyltin dimethoxide as an initiator/catalyst. Intercalated nanocomposites were formed either by melt blending with organo-modified montmorillonite or in situ polymerization within sodium montmorillonite. The barrier properties were studied for water vapor and dichloromethane as an organic solvent. The sorption ðSÞ and the zero concentration diffusion coefficient ðD 0 Þ were evaluated for both vapors. The water sorption increases with increasing the MMT content, particularly for the microcomposites containing the unmodified MMT-Na þ . The thermodynamic diffusion parameters, D 0 ; were compared to the value of the parent PCL: both microcomposites and intercalated nanocomposites show diffusion parameters very near to PCL. At variance exfoliated nanocomposites show much lower values, even for small montmorillonite content. In the case of the organic vapor, the value of sorption at low relative pressure is mainly dominated by the amorphous fraction present in the samples, not showing any preferential adsorption on the inorganic component. At high relative pressure the isotherms showed an exponential increase of sorption, due to plasticization of the polyester matrix. The D 0 parameters were also compared to those of the unfilled PCL; in this case, both the exfoliated and the intercalated samples showed lower values, due to a more tortuous path for the penetrant molecules. q

- by Vittoria Vittoria and +2
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- Engineering, Thermodynamics, Polymer, CHEMICAL SCIENCES

Microcapsules and nanocapsules containing n-octadecane with melamine-formaldehyde shell were fabricated by in situ polymerization. The effects of stirring rate, contents of emulsifier and contents of cyclohexane on diameters, morphology, phase change properties and thermal stabilities of the capsules were studied by using FT-IR, SEM, DSC and TG. The diameters of the microcapsules decreased with the increase of stirring rate, emulsifier content and cyclohexane content. The relationship between stirring rate and number-average diameters or weight-average diameters of the microcapsules is an exponent. The relationship between emulsifier content and number-average diameters or weight-average diameters of the microcapsules is an exponent, too. The diameters had less effects on the melting behaviour of microcapsules, however, they had significant effects on the crystallization behaviour. As the diameters of the microcapsules decreased, two crystallization peaks were observed from the DSC cooling curves. The ratio of the integrated area of the peak in the lower temperature increased with the decrease in diameters of microcapsules. The thermal stability of micro/nanocapsule rises with the increase of stirring rates and TA content. The cyclohexane content has no significantly effect on thermal stability of the nanocapsule.

Composites were synthesized by ''in-situ'' polymerization of polyazomethine, a liquid crystal polymer (LCP), in presence of multi-walled carbon nanotubes (MWNTs) previously dispersed in one of the employed monomers. Fiber processing was carried out by extrusion from the composites containing 1 and 10 wt.% of MWNTs at the mesophase temperature. We have observed that the typical highly oriented internal fibrillar structure can be significantly disrupted by increasing the nanotube content in the composite fibers. Evidences of MWNT alignment were found in the studied LCP/MWNT composites. D

- by Ana Benito
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- Materials Science, Biomedical Engineering, Carbon Nanotube, In Situ Polymerization

Electrically conductive elastomer blends based on polyaniline-dodecylbenzene sulfonic acid (PAni.DBSA/nitrile rubber (NBR) was prepared by polymerization of aniline in the presence of NBR, using a direct, one-step in situ emulsion polymerization method in which DBSA played both roles of surfactant and dopant. At the same PAni content, the conductivity of the in situ emulsion-polymerized blends is higher than that of blends produced by mechanical mixing of both components. In addition, a more uniform morphology with the presence of PAni in the form of microtubules was achieved by the in situ process. Stronger interaction between the components were also confirmed by the presence of great amount of insoluble material in non-vulcanized blends, by Raman spectroscopy and rheological processing analysis (RPA).

Montmorillonite/polypyrrole (MMT/PPy) nanocomposites, with 15% mass loading of PPy, were prepared by the in situ polymerization of pyrrole in the presence of montmorillonite (MMT) or organo-modified montmorillonite (oMMT) in aqueous solutions containing an oxidant and an anionic surfactant. The morphology of MMT/PPy nanocomposites distinctly differs from that of the untreated MMT as shown by SEM. X-ray photoelectron spectroscopy showed that the MMT/PPy nanocomposite has an MMT-rich surface, whereas the oMMT/PPy nanocomposite surface has a rather organic nature. Due to the organic modification of MMT by the alkylammonium chloride, polymerization of pyrrole at the surface of oMMT is much more efficient in producing a conductive adlayer resulting in an enhancement of conductivity of the oMMT/PPy nanocomposites (1.1 S cm À 1 ) compared to MMT/PPy (3.1 Â10 À 2 S cm À 1 ). The difference in the behaviour of oMMT/PPy and MMT/PPy is interpreted in terms of surface energy minimization by the alkylammonium ions present at the surface of organo-modified MMT. Indeed, the dispersive contribution to the surface energy (c s d ), as determined by inverse gas chromatography at 150 -C, was estimated to be 34.0 mJ/m 2 for oMMT, much lower than the value of 216 mJ/m 2 determined for MMT. D

The liquid crystalline compositions are prepared by the in-situ polycondensation of diamines and diacid monomers in the presence of single wall carbon nano tubes (SWNT). Processing of the new compositions into fibers provide hybrid materials with improved mechanical properties. The in-situ polymerizations were carried out in polyphosphoric acid (PPA). Carbon nano tubes as high as 10 wt.polymer weight have been

- by Thuy Dang
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- Materials Science, Scanning Electron Microscopy, Nitrogen, Composite Material

High impact polystyrene (HIPS) is a classical reactor polymer blend produced by in situ polymerization of styrene in solution with polybutadiene rubber. The importance of the particle size and rubber crosslink density on the particle cavitation capability and the controlling of toughening mechanisms in the styrenic matrix is well established in current literature. In the present work, the role of the rubber particle on the HIPS toughness has been investigated for two commercial grades with low and high cis polybutadiene. Transmission electron microscopy (TEM) was employed for observation of particle size distribution and digital imaging applied for quantitative analysis of the micrographs. Measurements of apparent volume fraction and average particle size were determined in TEM images for both grades, while the gel content and swelling index were employed to evaluate the effect of the polybutadiene cis isomer on the rubber crosslink density. Grade morphology and crosslink effects on mechanical properties were assessed by slow three-point bending and uniaxial tensile testing. The results illustrate that polybutadiene cis content in HIPS grades has strong influence on the mechanical properties, particularly affecting yielding and energy to failure. Accordingly, it was observed that HIPS grades with equivalent average particle size and apparent volume fractions present a much higher energy to failure and a lower yield stress with high cis content polybutadiene when compared to their lower cis polybutadiene counterparts.

- by Juliana Rovere
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- Engineering, Materials Science, Microstructure, Materials

Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio.

- by Uttandaraman Sundararaj and +1
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- Engineering, Carbon, Transmission Electron Microscopy, Electromagnetic Interference

An overview of polymer-clay hybrid nanocomposites is provided with emphasis placed on the use of alkylammonium exchanged smectite clays as the reinforcement phase in selected polymer matrices. A few weight percent loading of organoclay in nylon 6 boosts the heat distortion temperature by 808C, making possible structural applications under conditions where the pristine polymer would normally fail. A similar loading of clay nanolayers in elastomeric epoxy and polyurethane matrices dramatically improves both the toughness and the tensile properties of these thermoset systems. Glassy epoxy nanocomposites exhibit substantial improvement in yield strength and modulus under compressive stress-strain conditions. The latest development in polypropylene hybrids have yielded nanocomposites with improved storage moduli. Polyimide hybrids in thin-film form display a 10-fold decrease in permeability toward water vapor at 2 wt.% clay loading. In situ and melt intercalation processing methods are effective in producing reinforced polystyrene hybrids. Nitrile rubber hybrids show improved storage moduli and reduced Ž . permeabilities even toward gases as small as hydrogen. Poly´-caprolactone -clay nanocomposites prepared by in situ polymerization of´-caprolactone in organoclay galleries show a Ž substantial reduction in water adsorption. Polysiloxane nanocomposites produced from poly di-. methylsiloxane and organoclay mixtures have improved in tensile properties, thermal stability and Ž . resistance to swelling solvents. Organoclay-poly l-lactide composite film was obtained by solvent casting technique. Clay nanolayers dispersed in liquid crystals act as structure directors and form hybrids composites that can be switched from being highly opaque to highly transparent by applying an electric field of short duration. q 1999 Published by Elsevier Science B.V.

- by praveen M
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- Engineering, Earth Sciences, Nanocomposites, Thin Film

Ba (1 À x) La x Fe 12 O 19 (0.00 rx r 0.10) nanofibers were fabricated via the electrospinning technique followed by heat treatment at different temperatures for 2 h. Various characterization methods including scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and microwave vector network analyzer were employed to investigate the morphologies, crystalline phases, magnetic properties, and complex electromagnetic parameters of nanofibers. The SEM images indicate that samples with various values of x are of a continuous fiber-like morphology with an average diameter of 110 7 20 nm. The XRD patterns show that the main phase is M-type barium hexaferrite without other impurity phases when calcined at 1100 1C. The VSM results show that coercive force (H c ) decreases first and then increases, while saturation magnetization (M s ) reveals an increase at first and then decreases with La 3 þ ions content increase. Both the magnetic and dielectric losses are significantly enhanced by partial substitution of La 3 þ for Ba 2 þ in the M-type barium hexaferrites. The microwave absorption performance of Ba 0.95 La 0.05 Fe 12 O 19 nanofibers gets significant improvement: The bandwidth below À 10 dB expands from 0 GHz to 12.6 GHz, and the peak value of reflection loss decreases from À 9.65 dB to À 23.02 dB with the layer thickness of 2.0 mm.

Low-cost sensors were developed in two steps: (i) using a negative template to print graphite electrodes on vellum paper and (ii) coating with conductive polymers. Thin films of polyaniline (PANI) in the emeraldine oxidation state were investigated as active layers, after being synthesized by two routes: (a) polyaniline doped with dodecylbenzenesulfonic acid (DBSA) deposited by supercritical fluid (SC CO 2 ) and (b) PANI doped with hydrochloric acid (HCl) by the in situ polymerization method. The electrical response (mV) was measured with dedicated circuitry, both in static laboratory air and with a flow of dry nitrogen gas (N 2 ) at room pressure and temperature in a closed chamber, to assess the sensors for their sensitivity and reversibility. The phase morphology (microfiber structure) was characterized by FE-SEM. Results showed a difference in behavior between the sensors obtained by SC CO 2 coating with PANI and by in situ polymerization. The voltage in the SC CO 2 sensor decreased when it was exposed to the flow of dry nitrogen, whereas the opposite effect was observed in the other sensor.

- by Paulo Herrmann
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- Materials Engineering, Condensed Matter Physics, Conducting Polymer, Thin Film

Photoactive polyvinyl alcohol hydrogels (PVA) have been investigated for use as tissue engineering scaffolds. These materials allow in situ polymerization for minimally invasive implantation methods. The mechanical properties of these materials can be tailored for a variety of soft tissue applications. The Young's modulus and ultimate tensile strength of PVA hydrogels are increased with increasing polymer concentration, and highly elastic hydrogels can be formed by altering the number of crosslinkable groups per chain. Fibroblasts homogeneously seeded within 3 mm thick PVA hydrogels remained viable throughout 2 weeks in culture, with no differences in viability across the thickness of the hydrogel. Cells seeded within the PVA hydrogels also produce extracellular matrix proteins, as indicated by the production of hydroxyproline during culture. Intrinsically cell non-adhesive, these PVA hydrogels were functionalized with the cell-adhesive peptide RGDS and found to support the attachment and spreading of fibroblasts in a dose-dependent manner. These results suggest that photopolymerizable PVA hydrogels are promising for tissue engineering applications. r

- by Kristyn Masters
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- Biomaterials, Tissue Engineering, Cell Adhesion, Hydrogels

Highly conducting polyaniline (PANI)-multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by in situ polymerization. The FTIR and XRD show systematic shifting of the characteristic bands and peaks of PANI, with the increase in MWCNT phase, suggesting significant interaction between the phases. The SEM and TEM pictures show thick and uniform coating of PANI over surface of individual MWCNT. Based on observed morphological features in SEM, the probable formation mechanism of these composites has been proposed. The electrical conductivity of PANI-MWCNT composite (19.7 S cm −1 ) was even better than MWCNT (19.1 S cm −1 ) or PANI (2.0 S cm −1 ). This can be ascribed to the synergistic effect of two complementing phases (i.e. PANI and MWCNT). The absorption dominated total shielding effectiveness (SE) of −27.5 to −39.2 dB of these composites indicates the usefulness of these materials for microwave shielding in the Ku-band (12.4-18.0 GHz). These PANI coated MWCNTs with large aspect ratio are also proposed as hybrid conductive fillers in various thermoplastic matrices, for making structurally strong microwave shields.

- by Veena Choudhary
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- Materials Engineering, Materials Chemistry, Carbon Nanotube, Composite Material

Microencapsulated healing agents that possess adequate strength, long shelf-life, and excellent bonding to the host material are required for self-healing materials. Ureaformaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 µm in diameter were produced by appropriate selection of agitation rate in the range of 200-2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160-220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80-90%) of a free flowing powder of spherical microcapsules were produced with a fill content of 83-92 wt% as determined by CHN analysis.

- by Scott White
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- Electron Microscopy, Wound Healing, Scanning Electron Microscopy, Microencapsulation

There is a need to develop models that evaluate the interaction of wood adhesives at the macroscopic level to explain observations on the durability of bonded wood laminate products with changing moisture conditions. This paper emphasizes a model that relates durability to strain on the bondline caused by wood swelling. The effect of this strain is discussed in relation to two groups of adhesives with different chemistry, structure-property and adhesive-wood interaction relationship models. The in situ polymerized adhesive group involves highly cross-linked polymers with a rigid backbone that need to limit the swelling of the wood surface to provide a durable bond. The pre-polymerized adhesive group includes polymers with backbone flexibility and limited cross-linking so that they can thus distribute the swelling strain within the adhesive. These models emphasize the importance of the adhesive-wood interactions and end-use application for establishing the performance criteria.

... Microstructural investigations showed well-dispersed BaTiO 3 nanoparticles embedded in the polydiacrylate matrix. ... Polymerceramic nanocomposites have attracted interest for dielectric applications because they may combine the high... more

- by Patrick Grant and +1
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- Engineering, Materials Science, BARIUM TITANATE, Physical sciences

A versatile processing technique for fabricating epoxy nanocomposites with a high weight fraction of oxidized multi-walled carbon nanotubes is presented. Thin carbon nanotube based preforms were prepared through an oxidation-filtration protocol and then immersed in a pre-polymerized epoxy/curing agent solution in acetone. By adjusting the conditions for the oxidation of carbon nanotubes and the epoxy concentration in the as-prepared solution, high loading of graphitic nanostructures was obtained. Tensile tests indicated that the elastic modulus and strength of certain composites prepared by in situ polymerization as above were improved by 100% and 60%, respectively, compared to neat epoxy. In addition, the composite sheets showed comparable electrical conductivity values to the neat carbon nanotube paper. These results suggest that targeted chemical modification of the carbon nanotube surface is an effective way to enhance the electrical and mechanical properties of carbon nanotube-polymer composites.

- by Zdeno Špitalský and +2
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- Scanning Electron Microscopy, Nanocomposites, Carbon Nanotube, Nanotechnology

A novel, efficient, and easily synthesizable catalyst, an emeraldine form of polyaniline (PANI)21-hydroxyethane 1,1-diphosphonic acid salt (HEDP), was successfully synthesized and demonstrated as a reusable polymer-based solid acid catalyst in the synthesis of N-benzylidine-2-phenyl imidazo[1,2-a]pyridines with 2-aminopyridine with aromatic aldehydes and trimethyl silylcyanide at room temperature. PANI-HEDP was characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and conductivity measurements. Figure 4. TGA thermograms of the (a) PANI-HEDP and (b) recycled PANI-HEDP. Scheme 2. Synthesis of the imidazo[1,2-a]pyridines with a PANI-HEDP catalyst.

Coatings prepared from polyaniline-nano-TiO 2 particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10 wt% polyaniline prepared with different concentrations of nano-TiO 2 . The electrochemical impedance spectroscopy was studied at periodic intervals during exposure to hot saline (65 • C) conditions for prolonged durations over a period of 90 h. The open circuit potential (OCP) was found to shift with time from −0.38 V SCE to more anodic side (−0.2 V SCE) much above that of bare steel (−0.5 V SCE). The presence of nano-TiO 2 was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18 wt% nano-TiO 2 . The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nanosize TiO 2 , redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive.

In situ polymerization of pyrrole was carried out in the presence of fly ash (FA) to synthesize polypyrrole-fly ash composites (PPy/FA) by chemical oxidation method. The PPy/FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt%) of fly ash in pyrrole. The surface morphology of these composites was studied with scanning electron micrograph (SEM). The polypyrrole-fly ash composites were also characterized by employing X-ray diffractometry (XRD) and infrared spectroscopy (IR). The a.c. conductivity behaviour has been investigated in the frequency range 10 2 -10 6 Hz. The d.c. conductivity was studied in the temperature range from 40-200°C. The dimensions of fly ash in the matrix have a greater influence on the observed conductivity values. The results obtained for these composites are of greater scientific and technological interest.

Polyethylene nanocomposites containing silver nanoparticles with antimicrobial properties were produced via in situ polymerization. The silver nanoparticles were added together with the catalytic system (metallocene catalyst and methylaluminoxane, MAO, as cocatalyst) directly to the reactor. The polymerization activity did not present significant changes with the incorporation of the silver nanoparticles in comparison to the homopolymerization without filler. The effect of various silver nanoparticle contents on silver ion release and antimicrobial efficacy against Escherichia Coli were studied. Nanocomposites containing higher nanosilver concentrations (5 wt.%) showed the highest silver ion release, and after 24 h reached 99.99% of efficacy against the bacteria compared with the neat PE. Transmission electron microscopy (TEM) images showed that the nanospheres were well dispersed throughout the polyethylene matrix.

Epoxy-POSS based hybrid nanocomposites are prepared by in situ polymerization of a homogeneous blend of the diglycidylether of bisphenol-A (DGEBA) and 4,4'diaminodiphenylmethane (DDM) in the presence of octa(maleimidophenyl)silsesquioxane (OMPS). The reaction of a maleimido-functionalised POSS cube with the epoxy resin is studied by Fourier transform infrared (FTIR) analysis and the formation of nanocomposites is confirmed by wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA) studies indicate that the crosslinking structures of the nanocomposite networks are predominantly formed 2 between the terminal maleimide double bonds and the amino groups of DDM through a Michael addition reaction to form an aspartimide. The values of the glass transition temperatures (T g ) decrease with increasing POSS-maleimide content and this is likely to be due to the inclusion of POSS cages into the system and consequent increase in free volume. The dynamic thermal stability of the cured polymers is increased by increasing the POSS content in the hybrid epoxy matrices as evidenced from thermogravimetric analysis (TGA) data.

- by Ian Hamerton and +1
- •
- Materials Engineering, Scanning Electron Microscopy, bisphenol A, High performance polymers

Fluidic self-assembly is a promising pathway for parallel fabrication of devices made up of many small components. Here, we introduce 'railed microfluidics' as an agile method to guide and assemble microstructures inside fluidic channels. The guided movement of microstructures in microfluidic channels was achieved by fabricating grooves ('rails') on the top surface of the channels and also creating complementary polymeric microstructures that fit with the grooves. Using the rails as a guiding mechanism, we built complex one-and two-dimensional microsystems in which all the microstructures initially involved in the fabrication method were incorporated as components in the final product. Complex structures composed of more than 50 microstructures (each sized smaller than 50 µm) were fluidically self-assembled with zero error. Furthermore, we were able to use the rails to guide microstructures through different fluid solutions, successfully overcoming strong interfacial tension between solutions. On the basis of rail-guided self-assembly and cross-solution movement, we demonstrated heterogeneous fluidic self-assembly of polymeric microstructures and living cells. In addition to such assembly of in situ polymerized structures, we also guided and assembled externally fabricated silicon chips-demonstrating the feasible application of railed microfluidics to other materials systems.

- by Seung Ah Lee
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- Self Assembly, Multidisciplinary, Agile Methods, Interfacial Tension
- by Kadir Onder
- •
- Engineering, Materials Engineering, Physics, Condensed Matter Physics

Melamineeformaldehyde (MF) resin microcapsules containing decabromodiphenyl ether (DBDPO) with better thermal stability were successfully prepared by in situ polymerization, DBDPO being the core material and MF resins being the wall materials. Chemical structure of the prepared microcapsules was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Morphologies and thermal properties were also investigated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively. The results indicated that MF microcapsules with DBDPO particles prepared in this study showed better thermal stability, and could be used as effective flame retardant even for the resins which should be processed at temperatures higher than 350 C. Ó 2007 Published by Elsevier Ltd.

Recently, conducting polymer thin films have been investigated as transparent electrodes in photovoltaic devices and organic light emitting diodes. Due to its relatively high conductivity and excellent transmission in the visible region, poly (3, 4-ethyelenedioxythiophene) (PEDOT) has been shown to be a viable option for such applications. Herein described is a method for the vapor phase polymerization (VPP) of transparent PEDOT thin film electrodes on flexible polyethylene naphthalate (PEN) substrates and the comparison of this VPP method with two current approaches to PEDOT deposition: solution-based in situ polymerization and spin coating a dispersion of PEDOT:PSS. Electrical conductivities and UV-vis transmittances were measured for films produced by each of these methods, with VPP PEDOT showing both the highest conductivity (approx. 600 S/cm) and transmittance (>94% at 550 nm). The surface morphologies of the films were compared using AFM and SEM imaging. The stability of these PEDOT films, stored under ambient conditions, was investigated by monitoring the conductivity and transmittance of the thin films over time.

- by Christopher Madl
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- Materials Engineering, Condensed Matter Physics, Conducting Polymer, Thin Film

Poly(3-thiophene acetic acid)/Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe3O4 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe3O4 nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.Poly(3-thiophene acetic acid)/Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe3O4 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe3O4 nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.► Poly(3-thiophene acetic acid)/Fe3O4 nanocomposite is synthesized. ► Nanoparticles are superparamagnetic, with no saturation, coercivity, remenance. ► The crystallite and particle size are 9 ± 2 nm and 11 ± 1 nm as obtained by XRD and TEM. ► Magnetic particle size calculated from the theoretical fitting was 9.1 nm. ► These particle sizes’ comparison reveals magnetically dead nanoparticle surface.

- by Fatih Esat
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- Inorganic Chemistry, Image Analysis, X Rays, Grain size

The high-efficiency luminescent nanomaterials with different emission wavelengths of red (YVO 4 :Eu 3+ ), green (CePO 4 :Tb 3+ ), ZnS:Mn 2+ and YVO 4 :Eu 3+ @SiO 2 were successfully prepared with different concentrations of Mn and rare earth ions as active centres by chemical synthesis. Structure properties were studied. It was found that the particle size of our samples was in the range of 10-30 nm. Photoluminescent properties were studied under 325, 337, 365 and 370 nm excitations in order to apply in luminescent labels. The primary colour components are red and green emission making them very convenient and attractive for screen security printing systems. Hundreds of different labels with a size of 1-10 cm 2 were prepared by screen-printing as well as inkjet printing. By improving the Epson printer, commercial red, green and blue inks were used in the printing application. Screen and inkjet printing were deemed good methods for security printing. Our products were beautiful, high resolution and withstood tropical weather. . (2005) 'Luminescence and up -conversion mechanism of some photonic materials doped with Eu, Er and Yb ions',

- by Anh Tran
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- Transmission Electron Microscopy, Luminescence, Optical physics, In Situ Polymerization

Carbon nanotubes (CNTs) exhibit excellent mechanical, electrical, and magnetic properties as well as nanometer scale diameter and high aspect ratio, which make them an ideal reinforcing agent for high strength polymer composites. However, since CNTs usually form stabilized bundles due to Van der Waals interactions, are extremely difficult to disperse and align in a polymer matrix. The biggest issues in

- by santosh yadav
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- Engineering, Manufacturing, Carbon Nanotubes, Nanocomposites
- by maria R oliveira
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- Engineering, Carbon, Silica, Physical sciences

The use of clay nanofillers offers a potential route to improved barrier properties in polylactide films. Magnesiumealuminium layered double hydroxides (LDHs) are interesting in this respect and we therefore explored synthesis of PLA-LDH nanocomposites by ring-opening polymerization. This method is attractive because it should ensure good dispersion of LDH in the polymer. The effect of adding either LDH carbonate (LDH-CO 3 ) or laurate-modified LDH (LDH-C 12 ) was investigated. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy revealed that exfoliated nanocomposites were obtained when using LDH-C 12 but that LDH-CO 3 gave a partly phase-separated morphology. Thermogravimetric analysis showed that PLA-LDH combinations exhibited higher degradation onset temperatures and differential scanning calorimetry confirmed that LDHs can act as nucleating agents. However, PLA molecular weight was significantly reduced when in-situ polymerization was conducted in the presence of the LDHs and we suggest that chain termination via LDH surface hydroxyl groups and/or metal-catalyzed degradation could be responsible.

Pyrrole was polymerized onto commercial SFG10 graphite by in situ polymerization technique. Polymerization decreases the initial irreversible capacity loss of the graphite anode. The decrease in the irreversible capacity loss is due to the reduction in the thickness of the solid electrolyte interface (SEI) layer formed. PPy/C (7.8%) gives the optimum performance based on the irreversible capacity loss and the discharge capacity of the composite. The composite material has been studied for specific discharge capacity, coulombic efficiency, rate capability and cycle life using a variety of electrochemical methods. The composite SFG10 graphite possess good reversibility, higher coulombic efficiency, good rate capability and better cycle life than the bare SFG10 graphite. #

- by Jason Paul
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- Engineering, Lithium Ion Battery, Composite Material, CHEMICAL SCIENCES

Complementary thermal analysis techniques were used to study blending-induced perturbations in polymer dynamics pertaining to different motional lengthscales. The antiplasticizing role of common neutral and apolar fluorescent perylimides on the cooperative relaxation dynamics of poly(methyl methacrylate) (PMMA) chain segments is evidenced by a clear rise of both the glass transition (T g ) and liquid-liquid transition (T LL ) temperatures. Simultaneously, the dielectric strength, De b , of the signal ascribed to restricted rotational movements of lateral groups, shows a substantial reduction. Most aspects of the observed behavior bear analogies with recent experimental observations in nanoconfined PMMAs (e.g., PMMA with homogeneously dispersed SiO 2 nanospheres, in-situ polymerized in silica nanopores or in the form of supported ultrathin films), suggesting that a common mechanism is operational. In our mixtures, confinement effects, such as a modification in the macroconformation of the polymer, and changes in the orientation and packing of the polymer random coil, provide a plausible explanation of the observed changes regardless of the motional lengthscale concerned. Consonant with this scenario are reports of advanced optical properties for perylimide + PMMA blends, ascribed to the high rigidity of the matrix together with weak intercomponent interactions.

- by Fotini L Pallikari, PhD, MInstP, CPhys and +1
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- Materials Engineering, Chemical Engineering, Silica, Optical Properties

Acrylate and methacrylate anions containing double bond and carboxylic groups, were intercalated in the interlayer region of a layered double hydroxide of formula: [Zn 0.66 Al 0.34 (OH) 2 ](NO 3 ) 0.34 0.62H 2 O. The intercalation compounds obtained have been characterized for their chemical composition and with different instrumental techniques (X-ray powder diffraction, thermal analysis, FT-IR absorption spectroscopy, electron scanning microscopy). Furthermore, they have been used to carry out a preliminary study concerning the in situ polymerization of the intercalated acrylate and methacrylate ions to obtain new interstratified inorgano-organic hybrid materials. r

Nanocomposites based on poly(ethylene terephthalate)
(PET) and expanded graphite (EG) have been
prepared by in situ polymerization. Morphology of the
nanocomposites has been examined by electronic microscopy.
The relationship between the preparation method, morphology,
and electrical conductivity was studied. Electronic
microscopy images reveal that the nanocomposites exhibit
well dispersed graphene platelets. The incorporation of EG to
the PET results in a sharp insulator-to-conductor transition
with a percolation threshold (/c) as low as 0.05 wt %. An electrical
conductivity of 103 S/cm was achieved for 0.4 wt % of
EG. The low percolation threshold and relatively high electrical
conductivity are attributed to the high aspect ratio, large
surface area, and uniform dispersion of the EG sheets in PET
matrix.

- by S. Paszkiewicz and +2
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- Raman Spectroscopy, Nanocomposites, Nanoparticles, Transmission Electron Microscopy

Yttria-tetragonal zirconia polycrystal (ZrO 2 + 4.5 mol% Y 2 O 3 ) nanocrystalline powder was synthesized by two Pechini-type gel routes, the in situ polymerized complex (IPC) method and the PEG/AF method. FTIR spectra confirmed coordination of metal ions with the polymer by different routes, depending on the method used. The crystallite size of the powder increased from 5 nm to 8 nm when the temperature was increased from 450 8C to 600 8C and calcination times increased from 2 h to 24 h. The morphology of the powders differed only when the organic impurities were not completely eliminated. After calcination, the morphology of the powders produced by the two methods showed porous agglomerates composed of smaller particles. All the resulting microstructures were very similar, regardless of the method employed to obtain the powder or the calcination times and temperatures. #

- by Edson Grzebielucka
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- Engineering, Ceramics, CHEMICAL SCIENCES, Crystallite Size

Microcapsules containing curing agent for epoxy were successfully prepared by in situ polymerization with poly(melamine-formaldehyde) (PMF) as the shell material and high-activity polythiol (pentaerythritol tetrakis (3-mercaptopropionate), PETMP) as the core substance. Having been encapsulated, the core material PETMP had the same activity as its raw version. The synthesis approach was so improved that the consumption of polythiol was reduced to a low level. By carefully analyzing the influencing factors including catalyst concentration, reaction time, reaction temperature, feeding weight ratio of core/shell monomers, dispersion rate and emulsifier content, the optimum synthetic conditions were found out. The results indicated that not only core content and size of the microcapsules but also thickness and strength of the shell wall can be readily adjusted by the proposed technical route. The relatively thin shell wall (w0.2 mm) assured sufficient core content even if the microcapsules were very small (1-10 mm). The polythiol-loaded microcapsules proved to be qualified for acting as the mate of epoxy in making two-part microencapsulated healing agent of self-healing composites.

- by yan chao
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- Engineering, Materials Engineering, Civil Engineering, Scanning Electron Microscopy

Polyaniline (PANI) was obtained by in situ polymerization in a polystyrene sulfonic acid (PSS) solution. We prepared a series of PANI/PSS blends with molar ratio of 1:2, and PSS sulfonated at the degrees of 13 mol%, 21 mol% and 30 mol%. A control sample of polystyrene, at an intermediate sulfonation degree of 21%, without polyaniline, was also considered. The impedance spectroscopy, scanning electron microscopy and X-ray diffraction of the blends were evaluated. Increasing sulfonation degree increases the conductivity of the blends. Scanning electron microscopy (SEM) images allowed us to correlate the electrical properties of the blends with their morphologic characteristics. The smoothness of the blends surface observed by SEM increased with the sulfonation degree. X-ray diffraction indicated the increasing order with the sulfonation. This can be associated with homogeneous phase distribution, which results in highly conductive material.

Thermal energy storage as sensible or latent heat is an efficient way to conserve the waste heat and excess energy available such as solar radiation. Storage of latent heat using organic phase change materials (PCMs) offers greater energy... more

We demonstrate a comprehensive method for the fabrication and characterization of nanocomposite membranes containing vertically aligned single-walled carbon nanotubes. Preparation involves hydrodynamic self-assembly of carbon nanotubes, followed by encapsulation of the oriented CNTs in an in situ polymerized polyacrylic matrix. The top surface of the polymer film is removed by plasma etching to expose the carbon nanotube tips, leading to fast gas transport rates. Because the preparation method is potentially scalable to industrial-size membranes, it offers an attractive approach in the fabrication of single walled carbon nanotube membrane platforms.

- by Feras Rabie
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- Engineering, Membrane Science, Carbon, Carbon Nanotubes