Preparation and Thermal Characterization of PTFE/PES Nanocomposites

Summary: PTFE/PES composites were prepared by precipitation of Radel A® into a PTFE latex containing nanoparticles with average diameters of 48 nm and spherical shape. Several samples were prepared by varying the relative ratio between the Radel A® and PTFE content. The combination of SEM and AFM analysis indicates that the precipitation of Radel A in the presence of PTFE leads mainly, if not exclusively, to a bimodal mixture of the two homoparticles. The fractionated crystallization behaviour of these samples is revealing of the PTFE dispersion degree within the Radel A® matrix. When the PTFE amount is lower than 2%, a perfect PTFE nanoparticle dispersion is obtained. When the amount of PTFE is comprised between 5 and 30%, larger PTFE clusters are obtained that, after melting, coalesce and crystallize at higher temperatures depending on the crystallization propensity of their individual heterogeneous nuclei. Finally, in case of samples 40%, only one crystallization exotherm is observed at 310 °C indicating the formation of very large clusters that after melting coalesce into wide domains.     

Theoretical study on the mechanism of the CH2F + NO2 reaction

Despite the importance of the Fluoromethyl radicals in combustion chemistry, very little experimental information on their reactions toward stable molecules is available in the literature. Motivated by recent laboratory characterization about the reaction kinetics of Chloromethyl radicals with NO2, we carried out a detailed potential energy survey on the CH2F + NO2 reaction at the B3LYP/6-311G(d,p) and MC-QCISD (single-point) levels as an attempt toward understanding the CH2F + NO2 reaction mechanism. It is shown that the CH2F radical can react with NO2 to barrierlessly generate adduct a (H2FCNO2), followed by isomerization to b1 (H2FCONO-trans) which can easily interconvert to b2 (H2FCONO-cis). Subsequently, Starting from b (b1, b2), the most feasible pathway is the C--F and N--O1 bonds cleavage along with N--F bond formation of b (b1, b2) leading to P1 (CH2O + FNO), or the direct N--O1 weak-bond fission of b (b1, b2) to give P2 (CH2FO + NO), or the 1,3-H-shift associated with N--O1 bond rupture of b1 to form P3 (CHFO + HNO), all of which may have comparable contribution to the reaction CH2F + NO2. Much less competitively, b2 either take the 1,4-H-shift and O1--N bond cleavage to form product P4 (CHFO + HON) or undergo a concerted H-shift to isomer c2 (HFCONOH), followed by dissociation to P4. Because the rate-determining transition state (TSab1) in the most competitive channels is only 0.3 kcal/mol higher than the reactants in energy, the CH2F + NO2 reaction is expected to be rapid, and may thus be expected to significantly contribute to elimination of nitrogen dioxide pollutants. The similarities and discrepancies among the CH2X + NO2 (X = H, F, and Cl) reactions are discussed in terms of the electronegativity of halogen atom. The present article may assist in future experimental identification of the product distributions for the title reaction, and may be helpful for understanding the halogenated methyl chemistry.     

Spectroscopy of Methanol and Its Application to Optically Pumped THz FIR Lasers

In this paper, we have reviewed the details of experimental and theoretical aspects of the high-resolution molecular spectroscopy of methanol isotopomers. The methods of spectroscopic assignments and analysis have been discussed. The applications of the spectroscopic techniques, particularly of Fourier transform spectroscopy in the field of optically pumped Terra-Hertz Lasers (OPTL) and far infrared (OPFIR) lasers have been discussed. New assignments have been deduced for TEA-CO₂ laser pumped methanol and CW CO₂ pumped ¹³CD₃OD. Stark effect analyses and the determination of accurate dipole moment values have been discussed for CH₃OH, ¹³CH₃OH and CH₃ ¹⁸0H. The importance of high-resolution spectroscopy is also discussed in terms of astrophysical detection. Some recent ongoing astrophysical efforts are outlined. In our laboratory we are in the process of setting up a THz methanol laser for astrophysical applications and search for new coherent monochromatic laser sources.     

2,7-二辛基[1]苯并噻吩并[3,2-b]苯并噻吩(C8-BTBT)与MoS_2界面的能级匹配与薄膜生长

结合紫外光电子能谱(UPS)、X射线光电子能谱(XPS)和原子力显微镜(AFM)等实验手段系统研究了C8-BTBT沉积在层状Mo S2基底上的界面能级匹配、薄膜生长和分子取向。研究发现C8-BTBT分子竖直生长在Mo S2上,生长过程中界面的真空能级(VL)、最高占据态轨道(HOMO)和电离能(IP)都出现了非常规的弯曲现象。这种能级弯曲行为可归因于直立分子从界面相到体相的转变过程中,其分子倾斜角(θ)存在一定的渐变,这种渐变会在沿表面法线方向诱导出一系列的层间电偶极,最终导致能级的弯曲。同时θ的变化也会改变薄膜的表面极化强度,引起IP的逐渐减小。能级的弯曲在界面处形成类P-N结的效应会对C8-BTBT基电子器件的性能有很大的影响。     

Insights into the surface property and blood compatibility of polyethersulfone/polyvinylpyrrolidone composite membranes: toward high‐performance hemodialyzer

Applications of blood purification membranes are fuelled by diverse clinical needs, such as hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis, and plasma collection. For clinical usage, the adding of polyvinylpyrrolidone (PVP) is the general protocol for the design of antifouling and antithrombotic properties integrated artificial membranes. In the present work, to insight into the detailed surface properties and blood compatibilities of the PVP blended composite membranes, we synthesized a series of PVP polymers with different molecular weights using reversible addition fragmentation chain transfer polymerization and designed a series of polyethersulfone (PES)/PVP composite membranes by a physically blending method. The effects of PVP molecular weights and blending ratios on the surface properties and the blood compatibilities of the composite membranes were investigated in detail. The surface attenuated total reflection Fourier transform infrared spectra and scanning electron microscopy pictures indicated that the PVP was successfully immobilized into the membranes, and the composite membranes exhibited morphology transformation from finger‐like structure to sponge‐like structure, which indicated that the composite membrane had tunable porosity and permeability by adding PVP. The blood compatible tests revealed that the composite membranes showed increased hydrophilicity, decreased plasma protein adsorption, suppressed platelet adhesion, and prolonged blood clotting time compared with pristine PES membrane. These results indicated that the PES/PVP composite membranes exhibited enhanced antifouling and antithrombotic properties than the pristine PES membrane. Meanwhile, the results also suggested that the composite membranes with larger molecular weight PVP and higher blending ratios might show better blood compatibility. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel gaseous transient species:generation and characterization

Due to special properties of transient species,such as short-lived,unstable,reactive,and even explo-sive,the generation and subsequent characterization is a great challenge for experimental chemists. In our laboratory,systematic researches have been carried out to investigate novel transient species:reactive halogen species(RHS) ,short-lived free radicals,and metastable pseudohalogen compounds,based on the successive technical improvements on the HeI Photoelectron spectroscopy(PES) . In this review,the topic mainly focuses on innovative methods of generating novel transient species,and subsequent geometric and electronic structure characterizations of these species combined with quantum chemical calculations.     

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl-l-cysteine

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC₅H₈NO₃S·H₂O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state ¹³C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag-NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol, acetone and hexane. Antibacterial activity of the silver complex with N-acetyl-l-cysteine (Ag-NAC) was evaluated by antibiogram assays using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of a potential cytotoxic effect of Ag-NAC was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a significant cytotoxic activity, inducing 80% of cell death at a concentration of 200 μmol L⁻¹.     

Multifunctional PES fabrics modified with colloidal Ag and TiO2 nanoparticles

This study is aimed to highlight the possibility of engineering the multifunctional textile nanocomposite material based on the polyester (PES) fabric modified with colloidal Ag and TiO₂ nanoparticles (NPs). The effects of concentration of NPs as well as the order of Ag and TiO₂ NPs loading on antimicrobial, UV protective, and photocatalytic properties of PES fabrics were examined. The antimicrobial activity of differently modified PES fabrics was tested against Gram‐negative bacterium Escherichia coli, Gram‐positive bacterium Staphylococcus aureus, and fungus Candida albicans. The concentration of Ag colloid and the order of Ag and TiO₂ NPs loading considerably affected the antimicrobial efficiency of PES fabrics. The fabrics provided maximum UV protection upon surface modification with Ag and TiO₂ NPs. Ag NPs enhanced Ag NPs enhanced the photodegradation activity of TiO₂ NPs and total photodegradation of methylene blue was achieved after 24 hr of UV illumination. Copyright © 2010 John Wiley & Sons, Ltd.     

Spectroscopy and dissociation of sulfuryl halides SO2X2 (X=F,Cl)

The spectroscopy and dissociation of the sulfuryl halides SO₂F₂ and SO₂Cl₂ have been studied in detail using ab initio methods. The possibility of various dissociation channels has been explored taking into account that the fragmented atoms and molecules can stay in their ground state only. An interesting pattern was observed in their dissociation energy spectra for the dissociation channels. The singlet potential energy surfaces for the exit channels of these molecules have been analysed. The release of halogen molecules after dissociation is discussed from an industrial point of view. Finally, the enthalpy of formation of these molecules was computed using the ab initio results. Our results agree very well with the experimental values available.     

Preparation and Properties of Nano-Composite Films Based on Polyethersulfone and Surface-Modified SiO2

The interfacial interactions between inorganics and polymer matrix have important effects on the properties of nano-composites. A commercially available nano-SiO₂ was modified by surface pretreatment with sulfonated polyethersulfone, which is a typical polyethersulfone (PES) derivative, and served as a macromolecular modifier in this paper to fabricate PES/SiO₂ nano-composite films. The modified SiO₂ phase was well dispersed in polymer matrix due to its unique structure and the satisfactory interfacial interaction between nano-particles and the PES matrix. Compared with pristine SiO₂ as a ceramic filler, there was noticeable improvement in the transmission of light when modified SiO₂ was used. Effects of surface modification on thermal stability were also studied by thermo-gravimetric analysis.