Acetylation and molecular mass effects on barrier and mechanical properties of shortfin squid chitosan membranes

Chitosan samples with different N-deacetylation levels were obtained from β-chitin under heterogeneous alkali conditions. Oxidative depolymerisation was performed to attain low-acetylated chitosan samples with different molecular mass. Water vapour permeability, membrane swelling and tensile mechanical properties were analysed in plasticized self-supporting chitosan membranes. The main purpose was to describe unambigously the effect of the biopolymer molecular mass and acetylation degree on these properties. Commercially available chitosan samples derived from α-chitin were also studied for comparison. The equilibrium degree of swelling in water and the water vapour permeability increase by increasing the molecular mass or the degree of acetylation. Regarding the effect on the mechanical properties, generally harder and tougher membranes were obtained for chitosans with higher molecular mass or lower acetylation degree. These observations are tentatively explained based on the different structural characteristics of the polymer and can lead to a better understanding of the tools necessary to tailor a specific type of chitosan membrane.     

Time‐resolved Fourier transform infrared/attenuated total reflection spectroscopy for the measurement of molecular diffusion in polymers

Over the past 2 decades, the use of time‐resolved Fourier transform infrared/attenuated total reflection (ATR) spectroscopy for the measurement of diffusion in polymers has grown. ATR is a powerful technique for the measurement of diffusion in polymers because it is an in situ technique that is relatively inexpensive, provides reliable short‐time data, and provides a wealth of information at the molecular level. This article highlights the technique and its application to numerous studies, ranging from the diffusion of drugs in human skin to chemical warfare agents in barrier materials. In addition to these topics, recent studies with ATR to quantify and model molecular interactions during the diffusion process are reviewed. In the future, the ATR technique may have an impact on a variety of emerging fields in which diffusion in polymers plays an important role, such as fuel cells, membrane separation, sensors, and drug delivery. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2794–2807, 2003     

臭氧与二乙胺和三乙胺气相反应的速率常数

利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10^-17和(8.20±1.01)×10^-17 cm³·molecule^-1·s^-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区.     

臭氧与二乙胺和三乙胺气相反应的速率常数

利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10^-17和(8.20±1.01)×10^-17 cm³·molecule^-1·s^-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区.     

臭氧与二乙胺和三乙胺气相反应的速率常数

利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10^-17和(8.20±1.01)×10^-17 cm³·molecule^-1·s^-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区.     

Antifouling ultrafiltration membrane composed of polyethersulfone and sulfobetaine copolymer

A new random copolymer was synthesized by reacting hydrophilic N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) (DMMSA) with hydrophobic butyl methacrylate (BMA) through a conventional radical polymerization. The as-prepared sulfobetaine copolymer (DMMSA–BMA) was blended with polyethersulfone (PES) to fabricate antifouling ultrafiltration membrane for BSA separation. The X-ray photoelectron spectroscopy analysis of blend membranes revealed concentration of sulfobetaine groups at the membrane surfaces that endowed the membrane with higher hydrophilicity and better antifouling property. For the membrane with 8.0 wt% DMMSA–BMA copolymer concentration (No. 5), irreversible fouling has been considerably reduced and the flux recovery rate of the blend membrane reached as high as 82.8%. Furthermore, the blend membrane could effectively resist BSA fouling in a wide pH range from 4.0 to 8.0.     

Quantitative determination of paraffin oil in blood by capillary gas chromatography

A capillary gas chromatographic method is described for the quantitative determination of liquid paraffin in blood. Paraffin is extracted from blood into n-heptane. After solvent evaporation and dissolution of the residue in 100–200 μl n-heptane one μl is injected into a gas chromatograph fitted with a fused silica capillary column (Permabond® OV-1-CB-0.1, 10 m × 0.32 mm i.d.) and flame ionization detector. Analysis is performed by using an oven program [50°C (3 min)?285°C (5 min), rise 10%min]. The sensitivity (1.5 ng hexadecane) and the reproducibility prove the applicability of the method for the determination of liquid paraffin in blood and for the study of the stability of the liquid paraffin hollow fiber membranes used in an extracorporeal liver support system.     

C2H4-K体系中振动态至电子态传能的研究

用TEA CO_2激光将C_2H_4分子激发到高振动激发态，高振动激发态的C_2H_4分子与基态的K原子碰撞发生振动态→电子态（V→E）传能过程，根据提出的能级组模型，对测得的时间分辨原子荧光信号进行处理，获得温度在453－663 K范围内，C_2H_4-K体系中V→E传能速率的数量级为10~(-10)/cm~3·molecule~(－1)·s~(－1)，对应的碰撞传能截面约为0.30～0.80 nm．随着反应温度升高，V→E传能截面减小．上述实验结果表明碰撞体间吸引相互作用在这种非共振的V→E传能过程中起主要作用．利用多极相互作用势下的碰撞络合物模型对实验结果进行了讨论．     

The melt hollow fiber spinning process: steady-state behavior,sensitivity and stability

The rheology of the melt hollow fiber spinning process is examined in the thin filament limit. The resulting thin filament equations are also applicable to single-phase and two-phase extensional flows. Using a novel numerical solution procedure, the sensitivity of the fiber spinning equations to material property and process variations is investigated. Fiber geometry is directly controlled by the mass flowrates of the core and clad fluids while the spinline tension is most strongly influenced by clad viscosity. A maximum can occur in the clad stress profile if a core liquid is used and the ratio of core to clad viscosity increases greatly with temperature. Isothermal spinning of high viscosity clad liquids with either a core gas or liquid is unstable for draw ratios greater than 20.2 as found for solid fibers.     

N–N2 state to state vibrational-relaxation and dissociation rates based on quasiclassical calculations

Interpolation formulas are presented to reproduce the rate coefficients for vibrational–translational energy exchange and dissociation for the N + N₂ collision process. The original data have been obtained by quasiclassical method in a detailed way, including the effect of molecular rotation. The fitting procedure results are compared with original data and the related error is evaluated. Comparison with global experimental dissociation results is also presented.