Photochemical reduction of molecular weight and number of double bonds in natural rubber film

Natural rubber (NR) can be degraded depending on various factors such as heat, mechanical force, chemical reaction, and light. Light is a very interesting factor because it can cause the NR to degrade under low temperature and pressure. The photo-degradation of NR films was carried out to investigate the effects of the light and the temperature on the reduction of the weight-average molecular weight (Mw) and the double bonds in the NR films. The NR films, with and without catalysts, titanium dioxide (TiO₂), and potassium persulfate (K₂S₂O₈), were exposed to light from a mercury light bulb at 7,000 and 36,000 lux, and at the temperature of 25 °C and 80 °C for 192 hrs. After exposure, the Mw of the NR films was analyzed by gel permeation chromatography (GPC). Changes in the Mw were used to construct a kinetic model for the process, (1/Mw)=(1/Mw₀)+(kt/2M₀) where k is the rate constant, and M₀ is the Mw of the monomer unit. The linear relationship between 1/Mw and time suggested pseudo first-order processes with random scission. The Mw distribution information from the GPC was used to calculate the number of double bonds in the NR films. The trend of the double bonds reduction curves was quite similar to the result obtained from the calculation from the FTIR spectra. This indicated that this calculation method might possibly be another alternative way to obtain the number of double bonds in the NR.     

Effects and properties of poly(arylene ether benzonitrile)s of various molecular weights blended with sulfonated poly(ether ether ketone)

Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on polyacrylates containing pendant ligand with carbonyl and hydroxyl functions and their divalent metal complexes

A series of monomers were prepared by reacting (meth)acryloyl chloride with 2,4‐dihydroxybenzophenone, 2,4‐dihydroxybenzaldehyde, and 2,4‐dihydroxyacetophenone, respectively. The monomers were polymerized in dimethylformamide (DMF) at 70°C using benzoyl peroxide as an initiator. Polymer–metal complexes were obtained from DMF solutions of polymers with an aqueous solution of metal ions. The polymers and polymer–metal complexes were characterized by elemental analysis and spectral studies. The IR spectra of these complexes suggest that the metals are coordinated through the oxygen of the carbonyl group and the oxygen of the phenolic–OH group. The electronic spectra, electron paramagnetic resonance (EPR) spectra, and magnetic moments of polychelates showed an octahedral and square planar structure for Ni(II) and Cu(II) complexes, respectively. X‐ray diffraction studies revealed that polychelates are highly crystalline. The thermal and electrical properties, catalytic activity, and structure–property relationships are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2083–2090, 2003     

聚天冬氨酸的合成与表征

介绍了以L -天冬氨酸为原料 ,热缩合成聚天冬氨酸酐 ,水解得到聚天冬氨酸的合成工艺。采用凝胶色谱法测定了聚天冬氨酸的分子量 ,并用核磁共振对其进行了表征。     

聚天冬氨酸的合成与表征

以L-天冬氨酸为原料,热缩合成聚天冬氨酸酐,水解得到聚天冬氨酸。采用凝胶色谱法(GPC)测定了聚天冬氨酸的分子量,并用核磁共振(NMR)对其进行了表征。     

Improved methods for evaluating the molar mass distributions of cellulose in kraft pulp

Multi‐angle laser light scattering (MALLS) was used to characterize birch kraft pulps with respect to their absolute molecular mass distributions (MMDs). The pulps were dissolved in lithium chloride/N,N‐dimethylacetamide and separated by size exclusion chromatography (SEC). The weight‐average and number‐average molecular masses of the cellulose fractions of the pulps obtained from the absolute MALLS measurements were compared with the molar masses obtained by direct‐standard‐calibration relative pullulan standards. Discrepancies between the two detection methods were found, and two ways of correlating the relative pullulan molar masses to the absolute molar masses were examined. In the first method, the correlation was made over a large range of molecular masses. The second method correlated the molecular masses of the standards to the molecular masses of samples by the calculation of fictitious, cellulose‐equivalent molar masses of the standards. With the preferred second method, a more correct MMD of kraft pulp samples could, therefore, be obtained from an SEC system calibrated with narrow standards. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1170–1179, 2003     

网络控制系统随机延迟的预测控制

针对网络控制系统随机时延、时变等特性造成控制效果不理想的问题,提出一种改进的广义预测控制与递推最小二乘法相结合的预测控制策略.上述控制策略将传统的预测控制运用于网络控制系统中,针对网络随机时延的特性,采用改进的广义预测控制算法对随机时延进行补偿.结合分段可变遗忘因子递推最小二乘法对被控对象模型参数进行在线辨识,可以减少网络控制系统参数突变对系统造成的不利影响.仿真结果表明,所提出的预测控制策略可以有效解决网络控制系统随机时延问题,并且在参数突变的情况下也能够获得良好的控制效果.     

PID型广义预测控制在过热温控中的应用

在分析PID算法和广义预测控制算法的基础上,将广义预测控制算法的性能指标构造成PID形式,并推导出改进的PID型广义预测控制算法（PIDGPC）。通过在发电厂的过热蒸汽温度串级控制系统中的仿真,在时域内分析PIDGPC算法控制器的参数选择对控制性能的影响,说明PIDGPC算法比基本广义预测控制算法具有更好的控制性能,具有较好的应用前景。     

凝胶渗透色谱法检测淀粉酶解产物相对分子质量及其分布

运用普适校正原理,不需要Mark常数K、α值,使用示差折光检测仪及凝胶渗透色谱系统,直接测定了葡聚糖的相对分子质量及相对分子质量分布,优化了色谱操作条件,证明凝胶渗透色谱是监控淀粉酶解反应程度的一种有效手段.     

低聚KGM醛酸丙酯硫酸酯的结构分析

简要介绍了红外光谱、核磁共振、凝胶色谱等现代仪器分析方法的方法特点，以及在魔芋葡甘低聚糖及其两种衍生物(低聚KGM醛酸丙酯、低聚KGM醛酸丙酯硫酸酯)的结构分析中的应用。红外光谱和^1H—NMR图谱显示低聚KGM醛酸丙酯硫酸酯具有低分子类肝素的结构，凝胶色谱显示其相对分子质量为4000—3000。