Properties Of Organic Polymers Research Articles

The Development and Characterization of Polycaprolactone and Titanium Dioxide Hybrids

Organic/Inorganic hybrid materials have been attracting much attention since they combine the advantages of inorganic materials with the properties of organic polymers. Titanium dioxide nanoparticles (TiO2) present good thermal stability, accessibility and catalytic properties. Polycaprolactone (PCL) is a bi-ocompatible and bioresorbable material, which is being examined as biode-gradable packaging materials, controlled drug release carriers and other medical applications. Hybrids based on PCL containing different amounts of titanium dioxide nanoparticles, ranging from 0.05% to 0.35% w/w, were prepared using the solution cast method. These systems were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), low-field nuclear magnetic resonance (NMR), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The FTIR analysis confirmed that there was an interaction between the PCL chains and the TiO2 nanoparticles. The XRD and DSC analysis showed that the PCL crystallization was affected by TiO2 incorporation, modifying its semi-crystalline structure to a less ordered structure. When TiO2 nanoparticles were added the values of T1H and T1ρH increased for all hybrids, therefore, their addition produced a new material with less molecular mobility. In the TG analysis, it was observed that the introduction of TiO2 nanoparticles decreased the thermal resistance of PCL. In DSC analysis, the PCL/TiO2 hybrids presented a reduction in the crystallization temperature and degree of crystallinity, except for PCL hybrids containing 0.15% w/w of TiO2 nanoparticles.

Measurement of Nonlinearity and Spectral Study of a Laser Dye

Problem statement: The third order nonlinear optical properties of organic Polymers are used in high speed telecommunications, optical limiters and optical; computes. The purpose of study was to determine the spectral and third order nonlinear characteristics of the organic dye, Victoria blue in liquid and in solid medium. Approach: The samples were prepared by dissolving the dye in n-butyl acetate (liquid medium) and a thin film of thickness 1mm was prepared by bulk polymerization method. The spectral characteristics of victoria blue dye doped poly (methyl methacrylate) modified with additive n-butyl acetate (nBA) are studied by recording its absorption and fluorescence spectra and the results are compared with the corresponding liquid mixture. The nonlinear refractive index of the dye in nBA and dye doped polymer film were measured using z-scan technique [1], by exciting with He- Ne laser. The results obtained are intercompared. Results: Both the samples of dye Victoria blue in liquid and solid medium show a negative nonlinear refractive index. A negative nonlinear dye doped films can be used as optical limiters. The origin of optical nonlinearity in the dye may be attributed due to laser-heating induced nonlinear effect. PACS Code: 42.55.Mv, 42.65.-k, 82.35.Ej, 42.70.Jk

Hybrid polymer-based solar cells with metal oxides as the main electron acceptor and transporter

Hybrid polymer-based solar cells (HPSCs) that use conjugate polymers as electron donor (D) and inorganic semiconductor nanocrystals as electron acceptor (A) are novel photovoltaic devices. HPSCs integrate the properties of organic polymer (flexibility, ease of film formation, high absorption coefficient) and inorganic nanostructures (high electron mobility, high electron affinity, and good stability), and have the extra advantages, such as the rich sources of synthesized nanostructures by wet chemistry, tunable and complementary properties of assembled components, solution-processibility on a large scale at low cost and light-weight, etc. Amongst various inorganic semiconductor materials, the nanostructured metal oxides are the promising electron acceptors for HPSCs, because they are environment-friendly, transparent in visible spectrum and easy to be synthesized. After a brief introduction to the current research status, working principles, device architecture, steady-state and dynamic characterizations of HPSCs, this paper mainly reviews our recent research advances in the HPSCs using ZnO and TiO2 nanostructures as main electron acceptor and transporter, with emphasis on the theoretical models for charge carrier transport dynamics, design and preparation of efficient materials and devices, and the device performance related with nanostructural characteristics. Finally, the main challenges in the development of efficient HPSCs in basic researches and practical applications are also discussed. The main conclusions from our studies are summarized as follows: (i) IMPS and IMVS are powerful dynamic photoelectrochemical methods for studying the charge transport dynamics in HPSCs, and our theoretical models enable the IMPS to serve as an effective tool for the mechanistic characterization and optimization of HPSC devices. (ii) Using a multicomponent photoactive layer with complementary properties is an effective strategy to achieve efficient HPSCs. (iii) Using the complementary property of components, enhancing the dissociation efficiency of excitons, and improving the transport properties of the acceptor channels with reduced energy loss to increase collection efficiency all are the effective measures to access a high photocurrent generation in HPSCs. (iv) The band levels of components in the photoactive layer of HPSCs are aligned into type II heterojunctions, in which the nanostructured component with the lowest conduction band edge acts as the main acceptor/transporter; the maximum open-circuit voltage (Voc) in HPSCs is determined by the energy difference between the highest occupied molecular orbital (HOMO) level of conjugated polymer and the conduction band edge of the main acceptor, but the Voc in practical devices correlates strongly with the quasi-Fermi levels of the electrons in the main acceptor and the holes in the polymer. While passivating the surface defects on the main acceptor, increasing spatial e-h separation, and enhancing the electron density in conduction band of the main acceptor will facilitate the increase in Voc. (v) There is no direct correlation among Voc, photogenerated voltage (Vph) and electron lifetime (τe), and they may change in the same or the opposite trend when the same or different factors affect them, therefore one should get insight into the intrinsic factors that influence them when discussing the changes in Voc, V_{ph} and τe that are subject to nanostructural characteristics.

Explosive Sensing Using Polymer Lasers

Conjugated polymers are attractive materials that have been used to make a wide range of optoelectronic devices. Recently they have been used as explosive sensors as there is currently an urgent need for high sensitivity explosive detection due to the increased security issues across the world. This review outlines the attractive properties of organic polymers as gain media in lasers, and then focuses on the use of such lasers for explosive sensing applications. The combined advantages of fluorescent polymers and lasing promise explosive sensors with strongly enhanced sensitivity.

Synthesis of hybrid organic–inorganic nanocomposite materials based on CdS nanocrystals for energy conversion applications

Efficient solar energy conversion is strongly related to the development of new materials with enhanced functional properties. In this context, a wide variety of inorganic, organic, or hybrid nanostructured materials have been investigated. In particular, in hybrid organic–inorganic nanocomposites are combined the convenient properties of organic polymers, such as easy manipulation and mechanical flexibility, and the unique size-dependent properties of nanocrystals (NCs). However, applications of hybrid nanocomposites in photovoltaic devices require a homogeneous and highly dense dispersion of NCs in polymer in order to guarantee not only an efficient charge separation, but also an efficient transport of the carriers to the electrodes without recombination. In previous works, we demonstrated that cadmium thiolate complexes are suitable precursors for the in situ synthesis of nanocrystalline CdS. Here, we show that the soluble [Cd(SBz)2]2·(1-methyl imidazole) complex can be efficiently annealed in a conjugated polymer obtaining a nanocomposite with a regular and compact network of NCs. The proposed synthetic strategies require annealing temperatures well below 200 °C and short time for the thermal treatment, i.e., less than 30 min. We also show that the same complex can be used to synthesize CdS NCs in mesoporous TiO2. The adsorption of cadmium thiolate molecule in TiO2 matrix can be obtained by using chemical bath deposition technique and subsequent thermal annealing. The use of NCs, quantum dots, as sensitizers of TiO2 matrices represents a very promising alternative to common dye-sensitized solar cells and an interesting solution for heterogeneous photocatalysis.

Preparation and Characterization of the Hybrids Containing Silica Nanoparticles by Sol-Gel Crosslinking Process

The organic/inorganic hybrid nanomaterials containing silica nanoparticles are synthesized by sol-gel crosslinking process. The tetraethoxysilane (TEOS) and γ-aminopropyltriethoxylsilane as coupling agents are used as a precursor. The 2,4,6-tri [(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent is used to form covalent bonds among the inorganic nanoparticles. The chemical and morphological structures of the organic/inorganic hybrid are characterized with FTIR spectra, 29Si-NMR, x-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscope (AFM). The results show that the organic/inorganic hybrid forms covalent bond between the inorganic nanoparticle and Tri-EBAC. The network organic/inorganic hybrid can form good film with even nanometer particles. The network organic/inorganic hybrids nanomaterial not only exhibits the thermal properties of inorganic compounds, but also exhibits the thermal properties of organic polymer.

Dispersion behavior of core–shell silica-polymer nanoparticles

Core–shell silica nanoparticles are superior in modifying surface wetting behavior, enhancing nucleation and growth in crystallization, improving dispersion of naked nanoparticles, and thus upgrading the overall properties of organic polymers. The dispersion behavior and morphology of monodisperse core–shell silica particles in several polymers including polyesters are reviewed and their potential applications are discussed.

Main‐Chain Organometallic Polymers: Synthetic Strategies, Applications, and Perspectives

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Molecular and macroscopic NLO properties of organic polymers

AbstractTwo classes of aryltrienes in which the conjugation was incorporated in six‐membered rings have been developed. The microscopic nonlinear susceptibility, μβ, the product of the dipole moment and the second‐order nonlinear susceptibility, of these chromophores were measured using electric field‐induced second harmonic generation (EFISH). The chromophores were then copolymerized as side‐chain pendant groups in a methacrylate backbone copolymer with methyl methacrylate and their macroscopic electrooptic coefficients, r, were experimentally determined using a reflection technique after electric field poling of the polymers. When compared with 4,4′‐N,N‐dimethylaminonitrostibene (DANS), these molecules demonstrated electrooptic activities up to three times of DANS, when measured at 1.3 μm. By using a simple two‐level free‐gas model, the two sets of measurements corresponded closely at low poling fields. At high fields, the simple model breaks down as more detailed poling parameters are required to accurately describe the nonlinear poling effects. The results of the analysis of the high‐field poling data will be published separately. © 1994 John Wiley & Sons, Inc.

特集 有機フィルムと表面処理 有機高分子材料とフィルム

特集 有機フィルムと表面処理 有機高分子材料とフィルム

ChemInform Abstract: POLY(SULFUR NITRIDE), (SN)X, THE FIRST EXAMPLE OF A POLYMERIC METAL

Polymeric sulfur nitride, (SN) x , is an unusual substance, which although composed of non-metallic elements exhibits metallic properties and even becomes superconducting at very low. temperatures (0.3 K). The bonds between the polymeric chains are much weaker than within the chains. Therefore all electrical and mechanical properties are highly anisotropic. The preparation and crystal structure is described and a review is given of the physical investigations, especially of the electrical and optical properties and of the lattice dynamics. Parallels are drawn to the properties of organic polymers.