Alcohol Nanocomposite Films Research Articles

High Ionic Conductivity of Transparent Film of Hydroxyapatite and Poly(vinyl alcohol) Nanocomposite

AbstractSummary: Hydroxyapatite (HAp)‐polyvinyl alcohol (PVA) nanocomposite film containing Li+ was designed as a solid polymer electrolyte. A composite was prepared by reacting Ca(OH)2 with H3PO4 in the presence of PVA which is denatured in order to have the carboxyl group, and a LiN(CF3SO2)2 was added. HAp particles were commonly formed in the shape of spindles (long axis ca. 80 nm and short axis ca. 25 nm). The obtained nanocomposite film, in which HAp particles were dispersed uniformly, is transparent, flexible and drawable. Its ionic conductivity is about 10−3 S/m at room temperature. This value is very large. This high ionic conductivity is considerable on the basis of the dynamic percolation theory.

Evaluation of microstructure and photochromic behavior of polyvinyl alcohol nanocomposite films containing polyoxometalates

A series of photochromic nanocomposite films were prepared by well-dispersed Keggin type polyoxometalates (POM) in polyvinyl alcohol (PVA). The corresponding structure, photochromic behaviors and mechanism of the films were investigated with transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectra (FT-IR), ultraviolet visible absorption spectra (UV–vis) and electron resonance spectra (ESR). In composite films, the sphere-shaped POM nanoparticles were well dispersed with narrow size distribution. AFM images indicated that the surface topography of polymeric matrix changed after adding POM, and the surface appearance of nanocomposite films was different before and after ultraviolet light irradiation. FT-IR results showed that the Keggin geometry of POM was still preserved inside the composites and a charge-transfer bridge was built between POM and PVA polymeric matrix through hydrogen bonding. Irradiated with ultraviolet light, composite films changed from colorless to blue and showed reversible photochromism. The composite film containing molybdenum exhibited faster photochromic efficiency and slower bleaching reaction than that containing tungsten. The inferior reversibility of composite films was observed during the coloration–decoloration cycle. The appearance of the characteristic signals of W 5+ or Mo 5+ in ESR spectra indicated that PVA was a proton donor and the photochemical process was in accordance with the charge-transfer mechanism.

Ultrafast optical power limiting in free-standing Pt–polyvinyl alcohol nanocomposite films synthesized in situ

Free-standing platinum–polyvinyl alcohol nanocomposite films have been prepared by a simple in situ method. By thermal annealing, Pt nanoparticles of different sizes and shapes have been obtained. Their optical nonlinearity is measured using ultrafast (100 fs) laser pulses at 404 nm, in the absorption wing region. A strong optical power limiting is found in the films. The timescale of this limiting action is ultrafast, as it happens within the incident laser pulsewidth. Experimental results and numerical simulation indicate that the sign of the nonlinearity can be controlled by varying the film composition and annealing temperature. Use of ultrashort laser pulses in the free-standing film configuration permits a direct and unambiguous determination of the electronic nonlinearity of the material, since accumulative effects occur at later times lying outside the sharp measurement window.

Novel synthesis and optical properties of Sm 3+ doped Au- polyvinyl alcohol nanocomposite films

A new synthesis of samarium doped Au nano composite polymer films is described and the optical characteristics were analysed. Polyvinyl alcohol act as a reducing as well as capping agent. Optical absorption spectral analysis confirms the presence of Sm 3+ ions and the formation of Au nanoparticles. Au-surface plasmon band intensity increases with the increase of chloro auric acid concentration and the full width at half maxima (FWHM) is reduced, correspondingly. Using Judd–Ofelt theory the oscillator strengths were calculated for Sm 3+ ions. Photoluminescence studies has been carried out and it shows that the incorporation of the nanoparticles quenches the emission from the Sm 3+ ions.

Synthesis of Electroconducting Narrowly Distributed Nanoparticles and Nanocomposite Films of Orthanilic Acid/Aniline Copolymers

A unique strategy for synthesis of narrowly distributed and inherently self-stabilized copolymer nanoparticles by a simple emulsifier-free polymerization from orthanilic acid and aniline was developed. The polymerization yield, electrical conductivity, size, and its distribution of the nanoparticles could be simultaneously optimized by facilely regulating the comonomer ratio, oxidant/comonomer ratio, polymerization temperature, and time. In particular, the nanoparticles evermore exhibit a size polydispersity index down to 1.066 and strong redispersibility in water or polymer solutions. This facile synthesis of functional nanoparticles using orthanilic acid as vital comonomer readily affords yields up to 80%. A low percolation threshold of the nanoparticles/cellulose diacetate and poly(vinyl alcohol) nanocomposite films was found to be 0.18 and 0.07 wt %, respectively. This study opens a simple and general route for fabrication of nanostructured polymer materials with controllable size, narrow size distribution, intrinsic self-stability, strong dispersibility, high purity, and regulable electroconductivity.