Superparamagnetic maghemite/polyrhodanine core/shell nanoparticles: Synthesis and characterization

Maghemite nanoparticles (MNPs) with a thin layer of polyrhodanine (PRd) at the surface were synthesized via chemical oxidative polymerization of rhodanine monomer at the MNPs surface in the presence of ferric chloride as oxidant. X-ray diffraction (XRD) pattern gave direct evidence that the synthesized nanoparticles are crystalline maghemite of about 8 nm in size. Magnetization of the particles versus an applied magnetic field exhibited no hysteresis loop, indicated superparamagnetic behavior in the particles. Transmission electron microscopy (TEM) together with Fourier-transform infrared (FT-IR) spectroscopy were used to determine the morphology and the chemical structure of the magnetic core and the polymeric shell. Through the microscopy analysis the shell thickness was estimated to be about 1.5 nm, whereas through thermogravimetric analysis (TGA) it was estimated to be about 0.6 nm. Moreover inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements revealed that the oxidant residue in the polymer backbone is ca. 4 wt.%.     

Preparation and characterization of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) electrospun fibers

Ultrafine fibers of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) (CS/PVA/PVP) were prepared via electrospinning. The structure and morphology of CS/PVA/PVP ultrafine fibers was characterized by the Fourier transform infrared (FT-IR) spectroscope and scanning electron microscope (SEM). Furthermore, the effects of the concentration of PVA, PVP and the electrospinning voltage on the morphology of ultrafine fibers were investigated the the SEM. When the concentration of PVA was at the range of 30wt%–40wt%, ultrafine fibers could be obtained. The diameter distributions of ultrafine fibers decreased when the electrospinning voltage increased from 20 to 30 kV. The rough surface fibers could be obtained after etching with CHCl₃.     

MWCNTs/MOF-5杂化材料的制备及N_2吸附性能

通过改进的室温一步法制备了MWCNTs/MOF-5杂化材料,分别用XRD、FT-IR、TEM、FESEM、比表面积和孔隙度分析仪对MOF-5,MWCNTs/MOF-5进行了表征和分析。结果表明,碳纳米管的引入对晶体结构的影响不大;复合方式为碳纳米管"穿插"MOF-5的结构;MOF-5和MWCNTs/MOF-5在77 K和100 k Pa下N2吸附量最大,分别为873,743 cm-3/g,比表面积(BET)分别为2 435,1 866 m2/g。     

Synthesis and characterization of a novel poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl-CdS nanocomposites through chemical hybridization

A novel bi-functional photorefractive (PR) poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl with carbazolyl fragments and chromophoric azophenyl was synthesized by a post azo coupling reaction and characterized by ¹H NMR, elemental analysis, UV–Vis absorption and FTIR spectroscopy. Then chemical hybridized poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl-CdS nanocomposites with different molar ratio of CdS to poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl were prepared. It was confirmed that the CdS particles had a nanoscale size and quantum confinement effect adopting transmission electron microscopy and UV–Vis absorption spectroscopy. The generation of photocurrent on illumination and photoconductive properties of the nanocomposites were studied. Significant enhancement in photoconductivity induced by the chemical doping of CdS in poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl has also been demonstrated.     

Photoluminescence and thermal properties of erbium and ytterbium codoped poly(phthalazinone ether sulfone ketone) nanocomposites

Erbium and ytterbium codoped LaF₃ nanoparticles coated with organic ligands and Poly (phthalazine ether sulfone ketone) (PPESK) nanocomposites were prepared in this paper. The morphologies of nanoparticles were characterized by TEM. The thermal and photoluminescence properties of the PPESK nanocomposites were investigated by DSC, TGA and photoluminescence spectra. It was found that the nanoparticles with particle size of 20 nm can be homogeneously dispersed in PPESK-in-chloroform solutions, which allowed the transparent film to be facilely prepared. The photoluminescence spectra of PPESK nanocomposites film and solution in chloroform both reveal the typical features of the transition of Er³⁺ from ⁴I_13/2 to ⁴I_15/2 at 1530 nm. By adding nanoparticles to PPESK matrix, the T_g of PPESK has little change and the initial degradation temperature decreases.     

Morphological, viscoelastic and thermal properties of poly(vinylidene Fluoride)/POSS nanocomposites

Nanocomposites of poly(vinylidene fluoride) and polyhedral oligomeric silsesquioxane were prepared through melt blending. Morphology, viscoelastic and thermal properties were investigated. Up to 1 wt.% the processing conditions were efficient to prevent formation of large POSS agglomerates. In the nanocomposites with higher POSS contents these conditions could not avoid it, because of the strong interaction among POSS molecules. The presence of two different crystalline phases in nanocomposite was evidenced by X-ray diffraction and Fourier Transformed Infra-Red Spectroscopy. The nanocomposite with 5 wt.% content had the highest values for degree of cristallinity. The polyhedral oligomeric silsesquioxane molecules are acting as lubricant in the system, once lower values for storage modulus as well as for viscosity were observed.     

Synthesis, characterization and photoluminescence studies of ZnOrod@SnO2 nanocomposites

The synthesis of II-VI semiconductor (ZnO_rod@SnO₂) nanocomposite materials with core-shell morphology has been reported. ZnO nanorods were grown by hydrothermal technique using zinc acetate as the reactant. SnO₂ was coated on the nanorods by a simple technique of colloid chemistry. The formation of tin dioxide shell on the ZnO nanorods was confirmed by the TEM images of the resultant materials. The formation of the nanocomposite was also supported by XRD pattern. The effect of tin dioxide shell on the optical properties of ZnO was investigated by photoluminescence spectroscopy and Raman spectroscopy.     

Poly(aniline-co-m-aminobenzoic acid) deposited on poly(vinyl alcohol): Synthesis and characterization

In this work, we have deposited poly(aniline-co-m-aminobenzoic acid) on poly(vinyl alcohol) (PVA) by in situ polymerization. The polymerization was effected within maleic acid (MA) cross-linked PVA hydrogel. The copolymer was obtained by oxidative polymerization of aniline hydrochloride and m-aminobenzoic acid using ammonium persulfate as an oxidant. Instead of conventional solution polymerization, here synthesis was carried out on APS soaked MA cross-linked PVA (MA–PVA) film where the polymer was in situ deposited in its conducting form. The composite film was characterized by Fourier transform infra red (FT–IR) and ultraviolet visible (UV–VIS) spectroscopy and electrical measurements. Surface morphology of the composite films was studied by field emission scanning electron microscopy (FESEM). The variation of conductivity of the films was studied.     

Interface characterization and thermal degradation of ferrite/poly(vinylidene fluoride) multiferroic nanocomposites

Flexible multiferroic 0–3 composite films, with CoFe₂O₄, Ni_0.5Zn_0.5Fe₂O₄ or NiFe₂O₄ ferrite nanoparticles as filler and polyvinylidene fluoride (PVDF) as the polymer matrix, have been prepared by solvent casting and melt crystallization. The inclusion of ferrite nanoparticles in the polymer allows to obtain magnetoelectric nanocomposites through the nucleation of the piezoelectric β-phase of the polymer by the ferrite fillers. Since the interface between PVDF and the nanoparticles has an important role in the nucleation of the polymer phase, thermogravimetric analysis was used in order to identify and quantify the interface region and to correlate it with the β-phase content. It is found that an intimate relation exists between the size of the interface region and the piezoelectric β-phase formation that depends on the content and type of ferrite nanoparticles. The interface value and the β-phase content increase with increasing ferrite loading and they are higher for CoFe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄ ferrite nanoparticles. The composites shows lower thermal stability than the pure polymer due to the existence of mass loss processes at lower temperature than the main degradation of the polymer. The main degradation of the polymer matrix, nevertheless, shows increased degradation temperature with increasing ferrite content.     

Preparation,characterization and release of amoxicillin from cellulose acetate and poly(vinyl pyrrolidone) coaxial electrospun fibrous membranes

Electrospinning is a method that has been used to prepare polymeric fibers, with diameters ranging from nanometers to a micrometer of polymers such as cellulose acetate (CA) and poly(vinyl pyrrolidone) (PVP), and to develop membranes with applications in microencapsulation, for controlled release of drugs and for chemical and biological sensors. This work shows the feasibility and optimal conditions for the preparation of fibrous composite membranes of cellulose acetate and poly(vinyl pyrrolidone), via electrospinning, and their morphology; FTIR, and mechanical characterization and the effect of pH on the release of amoxicillin were analyzed. Tubes of CA with diameters around 500 nm were obtained. It was found that the release behavior of the drug from these fibrous membranes was dependent on the pH of the medium. It was observed that the amount of amoxicillin released as a function of time for a pH equal to 7.2 was approximately three times higher than that observed for a pH equal to 3.0. This suggests a greater interaction of amoxicillin with components of the membrane at a pH equal to 3.0, most likely due to the formation of hydrogen bonds. These materials have potential application in gastrointestinal administration and for transdermal patches.     

Synthesis, characterization, and catalytic application of highly ordered mesoporous alumina-carbon nanocomposites

Highly ordered mesoporous carbon-alumina nanocomposites (OMCA) have been synthesized for the first time by a multi-component co-assembly method followed by pyrolysis at high temperatures. In this synthesis, resol phenol-formaldehyde resin (PF resin) and alumina sol were respectively used as the carbon and alumina precursors and triblock copolymer Pluronic F127 as the template. N2-adsorption measurements, X-ray diffraction, and transmission electron microscopy revealed that, with an increase of the alumina content in the nanocomposite from 11 to 48 wt.%, the pore size increased from 2.9 to 5.0 nm while the ordered mesoporous structure was retained. Further increasing the alumina content to 53 wt.% resulted in wormhole-like structures, although the pore size distribution was still narrow. The nanocomposite walls are composed of continuous carbon and amorphous alumina, which allows the ordered mesostructure to be well preserved even after the removal of alumina by HF etching or the removal of carbon by calcination in air. The OMCA nanocomposites exhibited good thermostability below 1000 °C; at higher temperatures the ordered mesostructure partially collapsed, associated with a phase transformation from amorphous alumina into γ-Al₂O₃. OMCA-supported Pt catalysts exhibited excellent performance in the one-pot transformation of cellulose into hexitols thanks to the unique surface properties of the nanocomposite.     

Studies on polymer electrolyte poly(vinyl) pyrrolidone (PVP) complexed with ionic liquid: Effect of complexation on thermal stability,conductivity and relaxation behaviour

Polymer electrolyte films of PVP + x wt% ionic liquid (IL) (1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF₄]) for x = 0, 5, 10, 15, 20, 25 wt% have been prepared using solution cast technique. These films were characterized by TGA, DSC, FT-IR and ac impedance spectroscopy techniques. From XRD studies it is found that the inclusion of IL increases the amorphocity of polymeric membranes. DSC thermograms show that the glass transition (T_g) and melting temperatures (T_m) of PVP shift upon complexation with IL. FT-IR analysis shows the complexation of PVP with IL. Thermogravimetric studies show that PVP decomposes in a single step while PVP/IL membranes exhibit two step decomposition; lower value of decomposition temperature corresponds to the decomposition of PVP/IL complex while the higher decomposition temperature has been attributed to the decomposition of PVP. The decomposition temperature of PVP/IL complex decreases with the increasing amount of IL in the PVP membrane. Temperature dependence of conductivity and dielectric relaxation frequencies have also been studied for PVP and PVP/IL membranes. Both show thermally activated Arrhenius behaviour.     

硫酸酯化聚阴离子PVA的合成及表征

硫酸与聚乙烯醇(PVA)经酯化制备PVA聚阴离子电解质.分别考察了反应时间、反应温度等对取代度的影响.采用红外光谱(IR)、扫描电镜(SEM)对硫酸酯化PVA聚阴离子电解质的结构进行了表征,测定了其热稳定性和导电性.     

Preparation and characterization of micro and nanocomposites based on poly(vinyl alcohol) for packaging applications

In the present work, micro and nano composites based on poly(vinyl alcohol) matrix reinforced with cellulose (micro) and bentonite (nano) were obtained by film casting. The resulting composite materials were characterized by means of differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, FTIR spectroscopy, water absorption, permeability, and mechanical tests. The effect of the micro and nano fillers on the thermal, mechanical, and water absorption properties of the matrix was determined. The effects of polymer molecular weight and processing steps were also studied. Based on the results of the work, the potential biodegradability and the low cost of the starting materials, it can be concluded that the produced materials may be promising for packaging applications.     

Synthesis and characterization of novel Ag-polypyrrole@poly(styrene-co-methacrylic acid) nanocomposite particles

Novel raspberry-like Ag-polypyrrole/poly(styrene-co-methacrylic acid) (Ag-PPy/P(St-co-MAA)) colloidal nanocomposite particles were prepared by aqueous oxidative polymerization of pyrrole using AgNO₃ as the oxidant. The polymerization was carried out in the pre-synthesized polymer-emulsion of P(St-co-MAA) with emulsifier-free P(St-co-MAA) latex particles serving as both the templates and the stabilizers. Without any extra surfactants or polymer stabilizers, the polymerization proceeded steadily with the in-situ produced Ag-PPy nanocomposites depositing on the surface of the template particles. The obtained product is typical of raspberry-like morphology, whose nanostructures and compositions were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and electron dispersive X-ray spectrometer (EDS), respectively. The results confirmed that the surface of the P(St-co-MAA) latex was coated by Ag-PPy nanocomposite particles with a size range from 2 nm to 50 nm. Most of Ag nanoparticles are encapsulated by the PPy sheath or dispersed in the PPy layer.     

Preparation and characterization of poly(vinyl chloride) calcium carbonate nanocomposites via melt intercalation

Calcium carbonate was synthesized by in situ deposition technique and its nano size (35–60 nm) was confirmed by transmission electron microscopy (TEM). Composites of the filler CaCO₃ (micro and nano) and the matrix poly(vinyl chloride) (PVC) were prepared with different filler loadings (0–5 wt%) by melt intercalation. Brabender torque rheometer equipped with an internal mixer has been used for preparation of formulations for composites. The effect of filler content both nano- and micro level on the nanostructure and properties is reported here. The nanostructures were studied by wide angle X-ray diffraction and scanning electron microscopy. The mechanical, thermal, and dynamic mechanical properties of PVC/micro- and nano-CaCO₃ composites were characterized using universal testing machine, thermogravimetric analyzer, and dynamic mechanical analyzer. The results of thermal analysis indicated that the thermal stability of PVC/nano-CaCO₃ composites was improved as compared with corresponding microcomposites, and that of pristine PVC and maximum improvement was obtained at 1 and 3 phr loadings. However, the tensile strength decreased significantly with increase loading of both nano- and micro-CaCO₃, whereas storage modulus and glass transition temperature increased significantly.     

Nylon 66/poly(vinyl pyrrolidone) reinforced composites: 2: Bulk mechanical properties and moisture effects

The effect of interphase microstructure on the bulk mechanical properties and moisture absorption of Nylon 66 reinforced with E-glass or high-modulus (AS4) carbon fibers was examined. These particular composite systems were chosen because of their propensity to form distinct transcrystalline interphases. A comparison of mechanical properties was made by dynamic mechanical analysis (DMA) and Minimat off-axis tensile testing of samples with and without this unique interphase. Moreover, a newly developed vibrational testing technique was used and correlated with DMA to ascertain changes in the damping characteristics of the composites. The major contribution of this work is the systematic translation of single-filament (microscopic) results to bulk composite mechanical property results in the same well-characterized system. This was accomplished by studying both glass- and carbon-fiber/Nylon 66 composites. The E-glass- and carbon-fiber-reinforced Nylon 66 composites have better ultimate properties when the transcrystalline interphase is absent, but the composites have better damping properties when transcrystallinity is present. Finally, upon moisture exposure, suppression of the glass transition temperature was evident, as the water served as a plasticizer in all composites. The presence of transcrystallinity did not alter the adsorption kinetics of the composites.     

聚乙烯醇缩苯甲醛的合成与热稳定性研究

以聚乙烯醇（PVA）和苯甲醛为原料,二甲基亚砜为溶剂,对甲基苯磺酸为催化剂,采用均相工艺合成得到聚乙烯醇缩苯甲醛（PVB）。通过衰减全反射-傅里叶红外光谱（ATR-FT-IR）、紫外-可见光谱（UV-Vis）、核磁共振氢谱（1 H NMR）、核磁共振碳谱（13C NMR）等测试手段对聚乙烯醇缩苯甲醛结构进行了表征。利用差式扫描量热仪（DSC）测定了聚乙烯醇缩苯甲醛的玻璃化温度（Tg）。采用差热分析（DTA）和热重分析（TGA）对聚乙烯醇缩苯甲醛热稳定性进行了研究。DSC结果表明聚乙烯醇缩苯甲醛的玻璃化温度为106.0℃。DTA和TGA结果表明聚乙烯醇缩苯甲醛热稳定性良好,在空气中150℃仍未见分解。     

聚苯氧基磷酸对苯二酚酯的合成、表征及其热稳定性研究

以三氯氧磷、苯酚和对苯二酚为主要原料,通过两步合成法,采用本体聚合制备了含磷阻燃剂聚苯氧基磷酸对苯二酚酯。使用红外光谱、1 HNMR、13C NMR和31P NMR确定了阻燃剂的结构。用热重分析测试了阻燃剂的热稳定性。结果表明,聚磷酸酯的结构与预期结构相符;其初始分解温度为364℃,最快分解温度为547℃,700℃时的残炭量为36%,表现出良好的热稳定性。     

Structural characteristics and thermal properties of plasticized poly(l-lactide)-silica nanocomposites synthesized by sol-gel method

Plasticized poly(l-lactide)-silica nanocomposite materials have been successfully synthesized by sol-gel process. The resultant nanocomposites were characterized by infrared spectra (IR), X-ray diffraction (XRD), thermogravimetry (TG), Tensile testing and scanning electron microscope (SEM). IR measurements show that vibration of C-O-C group is confined by silica network. Also the crystallization of poly(l-lactide) is partly confined by silica network. The presence of even small amount of silica largely improves the tensile strength of the samples. TGA results reveal that the thermal stability of samples is improved with silica loading.