Preparation and properties of polythiourethane/ZnS nanocomposites with high refractive index

The inorganic–organic crosslinking polythiourethane/ZnS (PTU/ZnS) nanocomposites with high refractive index and transmittance were successfully prepared. The thiol‐capped ZnS nanoparticles with a diameter of about 5 nm were fabricated into the molecular chains of PTU via the formed covalent bonds between the capped ZnS and the matrix. The investigations demonstrated the ZnS nanoparticles were uniformly dispersed in the PTU matrix even at high contents. The optical studies showed the refractive index of the highly transparent nanocomposite films linearly increased from 1.643 to 1.792 with the increase of the ZnS content. The structure, morphology, and other properties were also characterized by FTIR, NMR, AFM, XRD, DSC, TGA, etc. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optical and physical properties of zirconium dioxide reinforced poly(methyl methacrylate) nanocomposite films

The objective of this study was to investigate the fundamental aspects of acrylic resin and zirconia nanoparticle interaction to analyze the optical properties and subsequent changes in refractive index with incremental loading of nanoparticles. Poly(methyl methacrylate) (PMMA) reinforced with zirconia nanoparticles were prepared by dip coating, spin coating and solvent casting techniques. An overall understanding of the polymer nanocomposite film has been achieved using the spectroscopic and morphological studies. The vital aspect of this whole study is to derive a simple yet an efficient nanocomposite film capable of imparting extraordinary optical properties. Within the limitations of this research a very crucial property of the material has been revealed. The RI as well as the optical transparency of the nanocomposite film has been steadily maintained with a significant increase of RI by the magnitude of 0.06 and ~100% light transmittance on incorporation of pure zirconia nanoparticles into PMMA matrix has been achieved. The best technique found was spin coating as it could yield thin films and better transparency and higher refractive index.     

Mechanical,optical, and electrical properties of cellulosic semiconductor nanocomposites

Photoluminescent cellulose fibers were prepared by impregnation of bleached bagasse pulp with the different cadmium and zinc sulfides nanostructures, namely, CdS, ZnS, CdS/ZnS, ZnS/CdS (Core/shell nanostructures), CdS/ZnS/CdS and ZnS/CdS/ZnS multilayered nanostructures. The prepared cellulosic nanocomposites were characterized regarding strength properties (tensile strength, tensile energy absorption, and burst resistance), optical properties (fluorescence emission), thermal stability, and dielectric properties. The strength properties of paper sheets nanocomposites impregnated with different nanoparticles solutions were noticeably decreased in spite of the very low loading of the fibers with the semiconductor nanoparticles. The decrease in tensile index, tensile energy absorption, and burst index of paper sheets nanocomposites are found to be ranged from 12–27, 13–36, and 11–38 %, respectively. The different paper sheets nanocomposites showed fluorescence emission different from the as prepared polyethyleneimine‐stabilized nanoparticles. Thermogravimetric analysis results showed that: the semiconductor nanoparticles did not affect the onset degradation temperature of cellulosic fibers but it caused faster termination of the main degradation step. The dielectric loss and the dc‐conductivity of cellulosic fibers increased as a result of impregnating the fibers. The nature of the nanoparticles and the properties of the interphases strongly influenced the dielectric properties of the cellulosic/semiconductors nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Design of particulate composites for optical applications

This paper reviews the basic theoretical approach to describing light scattering in filled materials with nearly matching refractive indices (Rayleigh-Gans-Debye Theory). The modifications necessary to handle high filler concentrations (interparticle interference and multiple scattering) are included empirically. The primary result of this analysis is an expression for the optical transmission of a polymer composite as a function of particle size, volume fraction, composite thickness, and refractive index difference between the components. The angular dependence of the scattering is included so that scattered light which falls within the aperture of the transmission detector can be accounted for, Particular attention is given to including the temperature dependence of the refractive index and the effect of fillers on the thermal expansion properties of the polymer matrix in order to predict the temperature range over which the composite will be optically useful. Similarity to analyses of the Christiansen filter is discussed.     

Nanocomposites of ZnS and poly-(dimethyl)-block-(phenyl)siloxane as a new high-refractive-index polymer media

ABSTRACT: In the present paper, we describe a new and original method to obtain transparent, siloxane-based composites, with high refractive index (up to 1.68). The method is based on the decomposition of Zn-siloxane, mixed with a poly-(dimethyl)-block-(phenyl)siloxane matrix in different ratios. It was found that after treatment of such mixed metal-containing polymer blend with H2S, the nanoparticles of ZnS are formed, with the size in a 1- to 5-nm range, which allow effective increase of the refractive index of the nanocomposite mixture with poly-(dimethyl)-block-(phenyl)siloxane without loss of film transparency. We succeded to increase the refractive index from 1.54 (pure matrix) up to 1.68 (composite with a ZnS content of 4.6 vol.%). The siloxane-based compositions are optically transparent, which makes it possible to use them as light-emitting diodes or solar cell sealants or adhesives.     

Fabrication of highly refractive,transparent BaTiO3/poly(methyl methacrylate) composite films with high permittivities

Incorporation of crystalline barium titanate (BT) nanoparticles into poly(methyl methacrylate) (PMMA) was carried out to prepare highly refractive polymer nanocomposite films that have transparency and high permittivities. The BT nanoparticles were prepared by hydrolysis of a barium/titanium complex alkoxide in 2‐methoxyethanol, then surface‐modified with a silane coupling agent (3‐methacryloxypropyltrimethoxysilane) to improve their affinity for PMMA. The incorporation of the surface‐modified nanoparticles into PMMA was performed up to a nanoparticle content almost equivalent to particle close‐packing state. The refractive index of the composite films increased with nanoparticle incorporation, keeping the relative transmittance normalized with PMMA film above 90%. A high refractive index of 1.82 was reached at a nanoparticle content of 53 vol% with a dielectric constant as high as 36 and a dissipation factor as low as 0.05. The results demonstrate that the crystalline BT nanoparticles are useful fillers for effectively increasing both refractive index and dielectric constant of polymer nanocomposites. Copyright © 2011 Society of Chemical Industry     

Preparation and characterization of novel ZnS/sulfur-containing polymer nanocomposite optical materials with high refractive index and high nanophase contents

A series of novel transparent bulk ZnS-polymer nanocomposites with high refractive index were successfully prepared via in-situ bulk polymerization in the presence of 2-mercaptoethanol (ME)-capped ZnS NPs. The polymerization mechanism combined the step-growth and free radical polymerization of different monomers of episulfide, m-xylylene diisocyanante (XDI), 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethylacrylamide (DMAA). The high refractive index of episulfide compounds, including ESGMES, ESDGEBA and MPS, were synthesized and used as monomers in polymerization systems. The cured nanocomposites with 30 wt% nanoparticles show high refractive index and good transparency. The refractive index of the nanocomposites could be continuously regulated in the range from 1.59 to 1.65 by the content of ZnS NPs and the pencil hardness is round about 5H. The content of ME-ZnS NPs can affect the thermal stability, mechanical and optical properties of the resulting nanocomposites, and the relationship between them were studied by TGA, DMA, pencil hardness test, Charpy impact test.     

Nanoinfusion of ZnO and ZnS nanoparticles into ethylene vinyl acetate in situ for improved optical properties

ZnO nanoparticles were successfully synthesized within the free volume of an ethylene vinyl acetate (EVA) polymer sheet. Using a process termed “nanoinfusion,” nanoparticles are created in situ. Vapor phase nanoparticle precursors first filled the polymer free volume. Nucleated components of the precursor molecule within the free volume enabled nanoparticle formation and immobilization within the polymer. Trapped nanoparticles were accessible to gas diffusion and can be modified as was demonstrated by the successful conversion of nanoinfused ZnO to ZnS nanoparticles. Successful nanoparticle formation was confirmed through fluorescence spectroscopy and the amount of material nanoinfused was obtained through thermal gravimetric analysis. The nanoinfused ZnO and ZnS exhibited unexpectedly high fluorescent quantum yields, significantly higher than that observed for comparable materials. © 2013 Society of Plastics Engineers     

Optical properties of particle‐filled polycarbonate,polystyrene, and poly(methyl methacrylate) composites

Transparency is a key material property of polycarbonate (PC), polystyrene (PS), and poly(methyl methacrylate) (PMMA). To study the optical properties of particle‐filled PC, PS, and PMMA, composites containing inorganic particles in different sizes and concentrations were produced by direct melt mixing in this work. The optical properties characterized by total light transmittance, haze, and clarity were studied. The results show that the optical properties of polymer composites are strongly affected by particle content, particle size, and especially by difference in refractive indices between polymer matrix and particles. It is also revealed that the light transmittance and haze of composites are mainly affected by difference in refractive indices, whereas the clarity is more affected by particle size. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of doped niobium pentoxide on structure and properties of hafnium oxide films deposited by ion beam assisted deposition

Hafnium oxide is widely used in optical coating materials because of its high refractive index, broad band gap, high laser damage threshold and its high transparency in the wavelength range from ultraviolet to middle infrared (0.20–12 μm). However, hafnium oxide has some defects such as strong crystallinity and poor surface quality, which results in enhanced absorption and reflection of light wave and limits its application in optical field. As a pentoxide with high transparency and excellent optical properties in the wavelength range from ultraviolet to mid-infrared(0.35–9 μm), the doping of niobium pentoxide can effectively improve the surface quality and optical properties of the films. Mixed films with different chemical compositions were prepared by ion beam assisted deposition, and the microstructure, crystallinity, surface quality, optical properties and mechanical properties of the mixed films with different chemical compositions were investigated. The doping of niobium pentoxide inhibits the crystallization of hafnium oxide, optimizes the surface quality of the films, and improves the refractive index and mechanical properties of mixed films, effectively broadens the application of hafnium oxide in the field of optical films.     

Investigation of optical and thermally stimulated properties of SiO2 nanoparticles‐filled polycarbonate

Polycarbonate nanocomposite containing silicon oxide nanoparticles average size of 5 nm at different weight ratio has been prepared by solution mixing method. The dispersion of nanoparticles in polymer matrix was studied by transmission electron microscopy (TEM). The optical and thermally stimulated behavior of nanocomposites were analyzed by energy dispersive X‐ray spectra (EDX), X‐ray diffraction pattern (XRD), UV–vis spectroscopy, differential scanning calorimetry (DSC), and thermally stimulated discharge current (TSDC). TEM images show the dispersion and size of the nanoparticles, however, EDX indicate the presence of SiO₂ on the surface of the nanocomposite film. An XRD result reveals that the crystallinity increases with increase in concentration of SiO₂ nanoparticles in polymer matrix. The direct and indirect optical energy band gaps decreased and number of carbon atom increased with concentration of SiO₂ nanoparticles. We have observed that the increase of SiO₂ nanoparticles in PC significantly reduces the refractive index. DSC and TSDC show that glass transition temperature increases according to SiO₂ weight ratio. The TSDC of nanocomposites samples could be understand in terms of non‐Debye theory of charge relaxation and co‐tunneling mechanism of charge transport. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flow birefringence of poly(n-hexyl isocyanate) solutions

A correction for optical quantities measured by a slit rheometer is proposed in order to obtain the corresponding optical properties at wall. This correction together with the Rabinowitch correction enables studies of the relation between the optical and the mechanical properties. A simple optical flow cell of a slit geometry was designed for the simultaneous measurements of the mechanical and the optical properties of flowing birefringent materials. The setup and the correction were applied to investigate the flow birefringence of the isotropic solutions of a liquid crystalline polymer, poly(n-hexyl isocyanate). The apparent birefringence defined as the refractive index difference between the ordinary light and the extraordinary light was found to increase with the increasing shear rates and was higher for solutions of high concentrations at a given shear rate. The stress optical law was checked. The ratio of the apparent birefringence to the shear stress was found to be independent of the shear rate at concentration of 10 wt%. For solutions of 15 and 20 wt%, the ratios increase with the shear rate when the shear rate is small, and they reach a maximum then decrease with increasing shear rate. The optical-stress behavior of PHIC solutions qualitatively follows the theoretical prediction of the Doi theory.     

Preparation and characterization of poly(vinyl alcohol)‐based magnetic nanocomposites. 1. Thermal and mechanical properties

CoFe₂O₄ magnetic nanoparticles were prepared by in situ precipitation and oxidation of Co²⁺ and Fe²⁺ within a sulfonated polystyrene resin. The nanometric particles were characterized by X‐ray diffraction. A ferrofluid was prepared from the CoFe₂O₄ mineralized polymer resin and water. Poly(vinyl alcohol) (PVA)‐based nanocomposite materials were obtained by mixing different amounts of ferrofluid (compositions ranging within 0–51 wt % of mineralized resin) with an aqueous solution of the polymer. The PVA composite materials were characterized by TGA, DSC, and stress–strain testing. The thermal and mechanical properties of PVA change with filler content, exhibiting an initial increase in these properties due to polymer–filler interactions. After a maximum value, at about 15 wt % of mineralized resin, the mechanical properties decrease probably due to particle aggregation which causes phase separation. The results obtained show that the nanoparticles are dispersed in the amorphous regions of the polymer, the crystalline zones remaining unaltered up to compositions as high as 30 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3215–3222, 2001     

Characterization of Lithium Ion-Conducting Blend Biopolymer Electrolyte Based on CH–MC Doped with LiBF<Subscript>4</Subscript>

Lithium ion-conducting polymer blend electrolytes based on chitosan and methylcellulose complexed with lithium tetrafluoroborate (LiBF₄) were prepared by a solution-casting method. The features of complexation of the solid polymer electrolytes were studied using X-ray diffraction techniques. Electrical conductivity of the prepared films was measured as a function of frequency at a different temperature. The increased trend of the electrical conductivity with increasing temperature and salt concentration can be attributed to increasing the mobility and number of lithium ions, respectively. The polymer electrolyte system exhibited Arrhenius-type, temperature-dependence ion conductivity behavior. Optical properties such as optical band gap, tail due to localized states and complex refractive index were estimated for present polymer electrolyte system from optical absorption measurement in the wavelength region 190–1100 nm. It was found that the optical direct band gap values shifted to lower energies upon addition of LiBF₄ salt up to 40 wt% dopant concentration, and showed an increasing tendency for a further increase in dopant concentration. The high refractive index for this composition (2.44–2.63) at visible wavelengths eminently suitable for optical applications.     

Development of optically transparent ZnS/poly(vinylpyrrolidone) nanocomposite films with high refractive indices and high Abbe numbers

A series of optically transparent ZnS‐poly(vinylpyrrolidone) (PVP) nanocomposite films with high refractive indices and high Abbe numbers have been prepared. Mercaptoethanol (ME) capped ZnS nanoparticles (NPs) were introduced into the PVP polymer matrix via simple blending with high nanophase contents. ME‐ZnS NPs of around 3 nm were prepared from zinc acetate and thiourea precursors in N,N‐dimethylformamide using ME as a capping agent. Transparent nanocomposite films with high refractive indices and high Abbe numbers can be easily prepared by a conventional film casting method. TGA results indicated that the ZnS/PVP nanocomposite films exhibit good thermal stability and the measured contents of ZnS NPs in the films agree well with the theoretical values. The refractive indices and the Abbe numbers of the ZnS/PVP nanocomposite films range from 1.5061 to 1.7523 and 55.6 to 20.4 with the content of ME‐ZnS NPs varied between 0 and 80 wt %, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

N-type silk fibroin/TiO2 nanocomposite transparent films: electrical and optical properties

This paper highlights the effect of different concentrations of titanium dioxide (TiO₂) nanoparticles on the electrical and optical properties of silk fibroin (SF). TiO₂ based SF nanocomposite films were prepared using the solvent casting method. Uniform dispersion and agglomeration of nanoparticles, in nanocomposite films, were observed by field emission SEM. The conductivity of pure SF and nanocomposite films was determined by a four-point probe and the TiO₂ nanoparticles were found to bring high conductivity to the nanocomposite films. Dielectric strength improved with the addition of nanoparticles to the SF matrix. Dielectric constant and capacitance of the pure SF and nanocomposite films were measured using an LCR meter, which showed a 10-fold enhancement on the addition of nanoparticles in SF. A very unusual property, i.e. negative resistance, was observed during LCR meter analysis for the nanocomposite films for a particular range of frequency (200–550 kHz), voltage (1 V) and current (0.5–1.5 μA). TiO₂ nanoparticles changed the semiconducting behavior of the SF films from p-type to n-type as measured by the Hall effect experiment. The optical properties of pure SF and nanocomposite films were measured using a UV–visible spectrophotometer. The increased concentration of nanoparticles in the SF has effectively enhanced the absorbing coefficient, refractive index and percentage transmittance and reduced the bandgap energy. These SF/TiO₂ nanocomposite films have shown the potential to be used as dielectric and high refractive index material for optoelectronics applications. © 2021 Society of Industrial Chemistry.     

Synthesis and characterization of ZnS/hyperbranched polyester nanocomposite and its optical properties

The ZnS/hyperbranched polyester nanocomposite with higher refractive index was prepared by incorporating the acrylated 2-(2-mercapto-acetoxy)-ethyl ester-capped ZnS nanoparticles into the acrylated Boltorn™ H20 (H20). The acrylated 2-(2-mercapto-acetoxy)-ethyl ester-capped colloidal ZnS nanoparticles were synthesized by the reaction of zinc acetate with thioacetamide in N,N-dimethylformamide. The acrylated hyperbranched polyester was obtained by reacting acryloyl chloride with hydroxyl group of H20. The acrylated H20 plays an important role in stabilizing and dispersing ZnS nanoparticles with a diameter of 1-4 nm. The refractive indices of ZnS/hyperbranched polyester nanocomposites, depending on ZnS content, were determined to be in the ranges of 1.48-1.65.     

Effect of aluminum oxide nanoparticles additives and gamma irradiation on the structural and optical properties of syndiotactic polystyrene

Aluminum oxide nanoparticles (Al₂O₃) were prepared and the obtained structure and size of the prepared Al₂O₃ nanoparticles were studied via X‐ray diffraction (XRD) and transmission electron microscopy. The effect of adding various concentrations of the Al₂O₃ and gamma radiation on the structural and optical properties of syndiotactic polystyrene (sPS) were investigated using XRD and UV‐spectroscopy. XRD data showed that the addition of the various concentrations of the Al₂O₃ influenced the crystallinity of the nanocomposites. A significant change in the lattice structure and the optical parameters were observed. The results showed that a sample with the Al₂O₃ concentration of 10% achieved a higher refractive index and optical conductivity. Effect of gamma irradiation on sPS sample loaded with 10% Al₂O₃ was studied. The results showed several changes in the structure and optical properties of the resulting films due to crosslinking between the polymer chains. This result reflects that the polymer suffered from structural rearrangement due to the irradiation treatments. POLYM. ENG. SCI., 59:555–565, 2019. © 2018 Society of Plastics Engineers