绿脓杆菌Pseudomonas aeruginosa BTE-1直接电催化特征

本文研究厌氧条件下产电绿脓杆菌P. aeruginosa BTE-1的电化学催化特征。研究结果表明,P. aeruginosa BTE-1菌株在厌氧条件下,不能分泌可充当电子介体的绿脓菌素,但可通过在电极表面形成生物膜呈现了直接电催化性能。P. aeruginosa BTE-1在电极表面形成生物膜与其在特定电极电位下向电极传递电子的过程直接相关,适宜的电位为+0.2 V (vs. SCE),电位过高可能会损害P. aeruginosa BTE-1细胞。室温范围内升高温度可增强P. aeruginosa BTE-1生物膜电催化活性,但过高的温度(>60℃)会抑制生物膜电催化活性。循环伏安曲线显示,在厌氧条件下形成的P. aeruginosa BTE-1生物膜,具有与典型产电菌株G. sulfurreducens相近的氧化还原电位(-0.4 V~ -0.2 V vs. SCE)。P. aeruginosa BTE-1生物膜可电催化酵母抽取物和葡萄糖,但不能电催化醋酸盐。     

Effects of substrate and transfer on CVD-grown graphene over sapphire-induced Cu films

We differentiated the effects of Cu films deposited on single crystalline a-,r-,and c-plane sapphire substrates upon graphene films synthesized with atmospheric pressure chemical vapor deposition(CVD).The data illustrate that the realization of high-crystalline Cu film is dependent not only on the crystallinity of underlying substrate,but also on the symmetric match of crystallographic geometry between metal film and substrate.We also systematically investigated the effects of PMMA removal on the Raman ID/IG and IG/I2D values of transferred graphene.The results reveal that different PMMA removal methods do not alter the ID/IG values;instead,the residue of PMMA increases the IG/I2D values and the thermal decomposition of PMMA leads to higher IG/I2D values than the removal of PMMA with acetone.The effects of PMMA removal on variations of the Raman spectra are also discussed.     

Photo-stability of photo-cured organic coatings: Part I—Secondary reactions in thioxanthone/amine photo-cured organic coatings

Luminescence measurements on 2-iso-propylthioxanthone (ITX) in a poly(methyl methacrylate) (PMMA) film as a model system were carried out to study the secondary reactions of ITX during and after photocrosslinking of organic coatings. The energy of the lowest excited triplet state (T₁) of ITX was calculated to be E₁₁ = 62·2 kcal/mol. The ITX triplet lifetime in a PMMA film was calculated from the phosphorescence decay to be τ = 1·0 ms. Irradiation of a PMMA film containing 4 mm ITX resulted in rapid photoreduction of the aromatic ketone. In a PMMA-benzene solution, studied for comparison, the photo-reduction rate was lower than in film. Triplet excited ITX may decompose peroxides by an energy transfer process. As the model system a mixture of tert-butylhydroperoxide and di-tert-butylperoxide was irradiated with uv light in the presence of ITX in benzene solution. This was found to give tert-butoxy radicals. The same radicals were formed by irradiation of a PMMA sample containing peroxides. The radicals formed were identified and measured using ESR spectroscopy combined with the spin trapping technique. The investigations reported here have established evidence for two important secondary reactions in the photo-curing of organic coatings using thioxanthone/amine as the initiating system: photo-reduction of ITX by hydrogen abstraction from the polymer and photo-decomposition of peroxides and hydroperoxides sensitized by thioxanthone.     

Electrochemical impedance spectroscopy of polybithiophene films in an aqueous LiClO4 solution

Polybithiophene (PBT) films (oxidized form), electrochemically deposited on Pt from an aqueous anionic micellar medium, were characterized by EIS measurements in 0.3 M aqueous LiClO₄ at different applied potentials. The EIS data were fitted with an equivalent electrical circuit in order to characterize the PBT electrochemical properties. Our experimental results show that both the double-layer and the film capacitances as well as the charge-transfer resistance decreased with the film thickness, while the diffusive capacitance and the charge-transfer and the pore resistance increased. Increasing the applied potential enhances the double-layer and film capacitances and the charge-transfer and pore resistances, but reduces the diffusive capacitance (with a minimum around the open-circuit potential) and the film resistance.     

Determination of Polycyclic Aromatic Hydrocarbons in Vegetables by Headspace SPME-GC

Inverse gas chromatography (IGC) at infinite dilution is a powerful technique to characterize the superficial and interfacial properties of solid substrates as oxides, polymers or polymers adsorbed on oxides. It can also be used to determine the physicochemical properties and the transition phenomena of polymers. In this paper, IGC was used to determine the changes, as a function of temperature, of the specific free enthalpy ??G _a ^SP and deduce the specific entropy ??S _a ^SP of poly (methyl methacrylate) (PMMA) adsorbed on alumina or on silica for different tacticities of PMMA. The study of the surface properties of PMMA/SiO₂ and PMMA/Al₂O₃, revealed an important difference in the physicochemical behaviour of oxides covered by various concentrations of PMMA. This study also highlighted an important effect of the tacticity of the polymer on the specific entropy of PMMA adsorbed on oxides.     

Interfacial tension measurement with the neumann triangle method

The interfacial tensions between polystyrene (PS) and poly(butylene terephthalate)

1 System. name: poly(tetramethylene terephthalate).

(PBT), PS/poly(methyl methacrylate) (PMMA), and PBT/PMMA pairs have been obtained by employing the Neumann Triangle method (NT). The results are in good agreement with those obtained by the breaking thread method. For the first time, the NT method was applied to a reactive polymer pair with an in-situ compatibilizer to measure the interfacial tension. We found that the interfacial tension of the PS/PBT system with a small amount of poly(styrene-co-glycidyl methacrylate)

2 System. name of glycidyl: 2,3-epoxypropyl.

(PS-GMA) is significantly reduced compared to that without PS-GMA.     

Syntheses and optoelectronic properties of four photochromic dithienylethenes

Four photochromic dithienylethene compounds, 1,2-bis(2-methyl-5-naphthalene-3-thienyl)perfluorocyclopentene 1a, 1,2-bis[2-methyl-5(p-fluorophenyl)-3-thienyl]perfluorocyclopentene 2a, 1,2-bis[2-methyl-5(p-ethoxyphenyl)-3-thienyl]perfluorocyclopentene 3a, and 1,2-bis[2-methyl-5(p-N,N-dimethylaminophenyl)-3-thienyl]perfluorocyclopentene 4a were synthesized, and their optoelectronic properties, such as photochromism in solution as well as in poly-methylmethacrylate (PMMA) amorphous films, fluorescences and electrochemical properties were investigated in detail. These dithienylethenes have shown good photochromic behavior both in solution and in PMMA amorphous film. All of them exhibited relatively strong fluorescence and gave a bathochromic shift upon increasing concentration in THF. The irreversible anodic oxidation of 1a, 2a and 4a was observed by performing cyclic voltammetry experiments.     

Effects of Zinc oxide nanoparticles on the morphology and viscoelastic properties of polyamide 6/poly(butylene terephthalate) blends

The morphology of polyamide 6/poly(butylene terephthalate)(PA6/PBT, 70/30, W/W) blends filled with pristine Zinc oxide(ZnO) nanoparticles and ZnO surface-modified by γ-glycidoxypropyltrimethoxysilane(K-ZnO) was investigated. The incorporation of ZnO and K-ZnO by one-step compounding both resulted in a smaller size and narrower distribution of PBT domains and the effect of ZnO was greater than K-ZnO. To reveal the underlying mechanism, two-step compounding in which ZnO or K-ZnO was premixed with PA6 or PBT was conducted and the finest morphology was achieved when mixing PA6 with premixed PBT/ZnO. Transmission electron microscopy(TEM) demonstrated that ZnO was distributed in PBT in all cases and K-ZnO was enriched at the interface except when K-ZnO was premixed with PBT. ZnO and K-ZnO caused a deterioration in the melt rheological properties of PBT, which played a dominating role in the morphological changes. In addition, the interfacial localization of K-ZnO enhanced the dynamic rheological properties of PA6/PBT blends substantially.     

Optical anisotropy of polymeric films measured by waveguide propagation mode determination

Extruded thin films of a liquid-crystalline charge-conjugated rigid-rod polymer poly(p-phenylenebenzobisthiazole), PBT, and a semicrystalline thermoplastic polyethylene-terephthalate (Mylar) were fabricated and examined for film thickness, refractive index, and linear attenuation coefficient. Optical waveguide modes were successfully induced on the polymeric films using a prism coupler at λ = 633 and 1300 nm. Highly consistent thickness values were obtained for the polymeric films. In addition, the anisotropic nature of the optical properties was determined using TE and TM propagation modes. A refractive index as high as 2.3 was observed on PBT film. The refractive index data suggested that the PBT and Mylar films were optically anisotropic with refractive indices n? (out-of-plane) invariably smaller than n∥ (in-plane). Large anisotropy was also discovered in the linear attenuation coefficient α, with α_∥/α_? ≈ 50 for the Mylar films. Complementary polarimetric and spectroscopic interference measurements were also applied to investigate the optical anisotropy of the extruded polymeric films. © 1992 John Wiley & Sons, Inc.     

Improvements of properties of asphalt by poly(methyl methacrylate) additives

This article presents the effect of adding poly(methyl methacrylate) (PMMA) with different molecular weights on the mechanical properties of asphalt in terms of durability, strength, and resistance to rutting. By controlling the time of reaction we obtained PMMA of two different molecular weights: PMMA1 and PMMA2. The ageing properties of polymer modified asphalts were studied using the thin film over (oven) a test. A hot storage stability test was carried out for polymer modified binder. The physical properties of asphalt modified with PMMA including penetration value and softening point were examined at two different temperatures. Resilient modulus test was evaluated by a Universal Testing Machine. Results showed that an incorporation of PMMA into asphalt binder has significantly improved its properties under studies. Indirect tensile strength test and durability performance of the modified asphalts was evaluated as well. The resulted modification was found to be dependent on the polymer molecular weight. The PMMA1 exhibited effective and cheerful results.     

In vitro cytotoxicity evaluation of natural rubber latex film surface coated with PMMA nanoparticles

In order to increase surface roughness of the sulphur-prevulcanized natural rubber (SPNR) film and, hence, decrease the direct contact between the rubber and skin, the poly(methyl methacrylate) (PMMA) latex particles were deposited onto the SPNR film grafted with polyacrylamide (SPNR-g–PAAm). The surface coverage of PMMA particles on the SPNR-g–PAAm increased with increasing latex immersion time, particle size and concentration. Prior to the in vitro cytotoxicity evaluation on L-929 fibroblasts, the SPNR and SPNR-g–PAAm coated with PMMA particles were extracted by using the culture medium. Results showed that the cytotoxicity effect could be significantly reduced by coating PMMA particles onto the rubber film. At the extract concentrations of ≤12.5% for 24 h at 37 °C, no toxicity potential was detected. The study will be helpful for development of gloves designed for the hypersensitive person.     

Synthesis,Characterization and Applications of a New Prussian Blue Type Material

This work reports on a material synthesized via 1‐butyl‐3‐methylimidazolium tetrachloroferrate and K₃[Fe(CN)₆]. Its structure and properties were characterized by IR, XPS, AFM and CV, which was inferred as Prussian Blue Type (PBT) material with particle size distribution between 80–120 nm and spike‐like aggregation from the characterization results. PBT is insoluble in acetone, water and ethanol uniformly, which gives magnetic properties. It can be reacted with 30 % H₂O₂, and produce gas bubbles when a voltage is applied. Modified on the glassy carbon electrode, the material showed obviously electrocatalytic activity to sodium nitrite, which has potential application prospect for sensors.     

PMMA: A key macromolecular component for dielectric low-κ hybrid inorganic-organic polymer films

Inorganic-organic composite and hybrid films find widespread applications for the development of functional materials. Polymer matrices with embedded inorganic fillers, nanoparticles or clusters are particularly appealing for optical, electronic, dielectric and magnetic applications. In particular, the development of hybrid layers with tailored dielectric properties represents a key issue in many technological fields.In this framework, poly(methyl methacrylate) (PMMA), due to its outstanding chemico-physical properties, represents a particularly suitable polymer component for the embedding of both microscopic and nanoscopic functional inorganic fillers. The wide use of such a matrix has to be traced back to the favourable combination of chemical and physical properties and easy processing. In this review, the main features and properties of PMMA, with a particular focus on dielectric ones, are firstly briefly described. Selected examples to illustrate the state-of-the art of its corresponding use as dielectric matrix are given and several examples are provided and surveyed.Finally, three case studies concerning PMMA-based hybrid films, produced for very different application fields, are described and discussed. The first example deals with the entrapment of micrometric zinc sulphide powders in PMMA, which acts as a host matrix for the electroluminescent particles in thick film-based Alternate Current Powder Electroluminescent Lamps (ACPELs). The second example describes the preparation of low-κ inorganic-organic hybrid dielectric films based on a PMMA-polyvinylchloride(PVC) blend and a hydrophobic silica powder functionalised on the surface with trimethylsiloxane groups (m-SiO₂). The composition of the investigated materials is [(PMMA)_x(PVC)_y]/(m-SiO₂)_z with z ranging from 0 to 38.3 wt% and x = y = (100 − z)/2. The third case concerns the use of PMMA as a matrix to embed zirconium oxoclusters through the formation of covalent bonds. The obtained material, characterised by a dielectric constant value remarkably lower (1.93 at 1 kHz and 25 °C) than in pristine PMMA (3.0 at 1 kHz and 25 °C), appears as very appealing for the development of microelectronic devices based on low dielectric constant polymer films such as, for instance, field-effect transistor (FET).These three cases are paradigms of three different approaches to composite and hybrid materials based on the embedding of particles in PMMA polymer matrix.     

Steady-state scratch testing of polymers

The paper extends the notion of steady-state cutting of polymers with a sharp tool to scratching. The analysis assumes there is separation at the tool tip (fracture) and the removed layer undergoes plastic shear. Results are presented for three polymers: PMMA, PC and PBT. For the tougher polymer, PC, smooth scratches were obtained and the modified cutting analysis works well provided that the wear on the initially sharp tip is accounted for. For the more brittle polymers, PMMA and PBT, rougher scratches were obtained and this is consistent with the notion that the polymers exhibited micro-cracking ahead of the tool tip, which led to rough surfaces being generated. The results demonstrate that the fracture toughness and the yield stress are controlling parameters in the scratching process and that a sufficiently high value of crack opening displacement COD (greater than about 10 μm) ensures that smooth scratches are obtained, as was the case for PC.     

Antifungal and Surface Properties of Chitosan-Salts Modified PMMA Denture Base Material

Chitosan (CS) and its derivatives show antimicrobial properties. This is of interest in preventing and treating denture stomatitis, which can be caused by fungi. Therefore, the aim of this study was the development of a novel antifungal denture base material by modifying polymethyl methacrylate (PMMA) with CS-salt and characterizing its antifungal and surface properties in vitro. For this purpose, the antifungal effect of chitosan-hydrochloride (CS-HCl) or chitosan-glutamate (CS-G) as solutions in different concentrations was determined. To obtain modified PMMA resin specimens, the CS-salts were added to the PMMA before polymerization. The roughness of these specimens was measured by contact profilometry. For the evaluation of the antifungal properties of the CS-salt modified resins, a C. albicans biofilm assay on the specimens was performed. As solutions, both the CS-G and CS-HCl-salt had an antifungal effect and inhibited C. albicans growth in a dose-dependent manner. In contrast, CS-salt modified PMMA resins showed no significant reduced C. albicans biofilm formation. Furthermore, the addition of CS-salts to PMMA significantly increased the surface roughness of the specimens. This study shows that despite the antifungal effect of CS-salts in solution, a modification of PMMA resin with these CS-salts does not improve the antifungal properties of PMMA denture base material.     

Synthesis of thermoplastic elastomers based on PET glycolysates: Study of their dielectric properties

Thermoplastic elastomers based on PET glycolysates were synthesized in the molten state according to a multistep process. Their chemical structures were studied (¹H NMR, triple detection, steric exclusion chromatography) as well as their thermal properties (ATG, DSC) and their morphology (AFM). Influence of hard segments composition on the different properties was investigated with the same ratio soft/hard segment. DSC study showed that these compounds had thermal properties similar to those of conventional thermoplastic elastomers (low T_g and high T_m). The association of PET with PBT segments seemed to harm the hard segments crystallization. SEC analyses showed that the compounds obtained had low molecular weights. Two factors seemed to explain the difference in properties between the compounds with and without glycolysate: a lower molecular weight of the TPE containing glycolysate, and a lower organization for materials containing both PET and PBT segments in respect to copolymer without glycolysate and containing solely PBT segments.Dielectric measurements showed properties close to those usually encountered for insulators used in electrical engineering. Glycolysate-free materials exhibited the best properties (high resistivity, low loss factor, slight variation of permittivity) and the materials exhibited interesting insulating properties (breakdown voltage up than 35 kV/mm_RMS, resistivity around 10⁹ Ωm). An improvement of the synthesis methodology with the use of catalyst might result in a significant enhancement of the dielectric properties, already promising for this type of materials.     

Luminescence of monolayer thin films of the fully conjugated rigid‐rod polymer poly(p‐phenylenebenzobisthiazole)

Poly(p‐phenylenebenzobisthiazole) (PBT) is a heterocyclic, aromatic rigid‐rod polymer with a fully conjugated backbone and excellent dimensional, thermo‐oxidative, and solvent stabilities. A PBT polymer with an intrinsic viscosity of 18.0 dL/g was dissolved in methanesulfonic acid or Lewis acid. The PBT solution was spin‐coated and doctor‐bladed for freestanding films or onto an indium tin oxide (ITO) substrate. The acid was removed via coagulation. Scanning electron microscopy determined that the resultant film thicknesses were about 340 and 60 nm for PBT freestanding films and films on the ITO substrate, respectively. X‐ray scattering demonstrated that the freestanding films were in‐plane isotropic without long‐range order. The freestanding films were excited with a He‐Cd laser at 325 nm for photoluminescence (PL) response. PL spectra showed a distinct intensity maximum at 580 nm, regardless of the film‐forming conditions. After the films cooled to 67 K, the PL maximum shifted to 566 nm with enhanced intensity. Aluminum was evaporated onto the monolayer PBT thin film on the ITO substrate as an electron injector for electroluminescence (EL) response. Diodic electric behavior was observed for all monolayer PBT EL devices for the first time. A threshold voltage as low as 4 V was achieved for the monolayer EL devices. In addition, PBT EL spectra were tunable, with a maximum intensity at 570 nm at a bias voltage of 4.5 V changing to 496 nm at 7.5 V (i.e., a blueshift) with greatly increased intensity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1760–1767, 2002     

Additive Effects of Lithium Salts with Various Anionic Species in Poly (Methyl Methacrylate)

We report that lithium salts in lithium-ion batteries effectively modify the physical properties of poly (methyl methacrylate) (PMMA). The glass transition temperature (T_g) is an indicator of the heat resistance of amorphous polymers. The anionic species of the salts strongly affected the glass transition behavior of PMMA. We focused on the additive effects of various lithium salts, such as LiCF₃SO₃, LiCOOCF₃, LiClO₄, and LiBr, on the T_g of PMMA. The large anions of the former three salts caused them to form macroscopic aggregates that acted as fillers in the PMMA matrix and to combine the PMMA domains, increasing T_g. On the other hand, LiBr salts dispersed microscopically in the PMMA matrix at the molecular scale, leading to the linking of the PMMA chains. Thus, the addition of LiBr to PMMA increased T_g as well as the relaxation time in the range of glass to rubber transition.     

The microenvironment in polymer solids with added plasticizers. An attempt to measure the size and distribution of free volume in poly(methyl methacrylate) solids

Various amounts of n-alkylbenzenes (C_n: C₆H₅-C_nH_2n+1 (n = 3-16)) were doped into poly(methyl methacrylate) (PMMA) films, and the emission and thermal properties of each film were measured in detail together with their solid-state ¹³C NMR spectra. The aim of the present work was to estimate the size distribution of free volume in amorphous regions of polymer solids heavily doped with plasticizers by using C_n as models of a plasticizer. The excimer fluorescence yields of C_n in PMMA were found to depend on both the amount of C_n and the length of the alkyl chains of C_n, although the fluorescence spectra of all of the C_ns in dilute fluid solution were almost the same. The quantitative analysis showed: (1) C_n with n ? 12 induces a phase separation in PMMA, in which almost all of the C_n molecules are in a separated phase, and thus they cannot penetrate regions in which PMMA chains are aggregated. This means that C_n with n ? 12 cannot enlarge the space between PMMA chains. (2) Smaller C_n (n < 11) can enter free volumes between PMMA chains that correspond to their molecular size, but they can enlarge them only to a limited extent. Thus, the amount by which plasticization can increase the free volume of PMMA is limited by the size of the dopant and the inherent free volume of the polymer matrix. (3) The efficiency of excimer formation was found to reveal the maximum amount of C_n that could fit in the free volume of PMMA. Thus our fluorescence measurements showed that PMMA solids that were plasticized to their limit had a free volume that was larger than the volume occupied by all the conformers of C₅ and smaller than the volume occupied by almost all the conformers of C₁₂. In conclusion, we were able to obtain information on plasticization and to demonstrate a method of monitoring microenvironments in polymer solids after they have been doped with plasticizers.