聚苯乙烯接枝淀粉纳米晶的制备

通过淀粉纳米晶与苯乙烯乳液聚合的方法制备了聚苯乙烯接枝淀粉纳米晶并用FTIR和1HNMR进行了表征;制备了不同接枝聚苯乙烯单体与淀粉纳米晶的物质的量之比(MS)的聚苯乙烯接枝淀粉纳米晶,在苯乙烯单体和淀粉纳米晶摩尔比(M/SN)为2,反应时间为5～12h条件下,所得MS为0.15～0.67.X-射线衍射结果表明,接枝聚苯乙烯几乎不会改变淀粉纳米晶的晶型,但结晶度随着MS的增加而下降.     

Enzymatic degradation of 3D scaffolds of starch-poly-(?-caprolactone) prepared by supercritical fluid technology

Starch-based polymers have been proposed for different tissue engineering applications due to their inherent properties. In this work, a polymeric blend of starch-poly-(?-caprolactone) (SPCL) was processed using supercritical fluid technology, namely, by supercritical assisted phase inversion. As SPCL is a biodegradable polymer, the matrices produced are susceptible of undergoing enzymatic degradation upon implantation in the human body. In vitro assessment of the enzymatic degradation of SPCL was carried out in different buffer solutions containing α-amylase and/or lipase. The effect of the presence of these enzymes was studied by monitoring different parameters in order to characterise both bulk and the surface of the scaffolds. As regards to bulk analysis, weight loss of the samples incubated for 1, 3, 7, 14 and 21 days was determined, further differential scanning calorimetry was carried out. The morphology of the scaffolds after these periods was analysed by micro-computed tomography (μ-CT) and surface chemistry was characterised by infra-red spectroscopy and contact angle measurements. Results suggest that SPLC scaffolds undergo bulk degradation, which is typically characterised by hydrolysis of chemical bonds in the polymer chain at the centre of the matrix, resulting in a highly porous material.     

稻米淀粉崩解值的近红外透射光谱法测定

以203份稻米为样品,近红外透射光谱分析仪,对样品进行光谱扫描,并用快速粘度分析仪测定稻米淀粉崩解值.采用改进的偏最小二乘法进行定标模型的建立,得到了稻米淀粉崩解值测定的近红外分析模型的定标标准偏差(SEC)、交叉检验标准误差(SECV)和定标决定系数(RSQ)分别为:10.62、10.8和0.984,内部交叉验证的经校正的工作标准差(SEP)、检验偏差(BIAS)和交叉检验相关系数(1-VR)分别为:6.139、-0.362和0.939,相关性达极显著水平.内部交又验证和外部验证结果表明近红外定量分析崩解值有很高的准确度.近红外透射光谱技术为快速准确无损测定黏滞特性指标提供了一条新途径.     

Simple flow injection system for colorimetric determination of iodate in iodized salt

This work presents a flow injection (FI) system that was developed for determination of iodate. The system utilizes the oxidation of iodide by the analyte to iodine, which subsequently forms tri-iodide. In the presence of starch, the blue I₃⁻–starch complex is developed within the sample zone and can be colorimetrically detected at 590 nm. Optimization was carried out to make the system suitable for quantitating iodate added to table salts. To prevent accumulation of the blue complex residue on walls of tubing and the flow cell, a port was placed in the system for injection of 10⁻³ M thiosulfate plug (100 μl). An injection of this cleaning solution after each sample injection is recommended to avoid positive baseline shift. By means of the paired t-test, the amounts of iodine (mg I kg⁻¹) were statistically compared with the results determined by titration and by iodide ion selective electrode. No significant disagreement at 95% confidence was observed. The proposed system is very simple, uses common chemicals and provides rapid analysis (65 injections per h) with high precision (R.S.D.=0.66%, n=10). A detection limit of 2 mg I kg⁻¹ salt can be achieved.     

Viscoelastic behaviour of wheat starch pastes

Summary The dynamic mechanical behaviour of starch pastes has been investigated over a frequency range of 0.02 to 5.0 radian sec^–1. The influence of concentration of starch, source of starch and method of paste preparation on rheological properties have been studied. The results suggest that under the conditions examined differences in the dynamic rigidity and viscosity of pastes may be attributed to differences in the number fraction of large granules and the volume fraction of swollen starch particles they contain.With 4 figures and 4 tables     

Rheology and morphology of starch/synthetic polymer blends

Corn starch and maleic anhydride functionalized synthetic polymers were melt blended in a Haake twin-screw extruder. The amount of starch in the blends was 60 and 70% by weight. The synthetic polymer used was either styrene maleic anhydride (SMA) or ethylene propylene maleic anhydride copolymer (EPMA). The blends did not exhibit normal thermoplastic behavior; and hence, rheological data was obtained by extrusion feeding the material through a slit die or cylindrical tube viscometer. The starch/SMA blends were extruded through a slit viscometer with a 45% half entry angle, while the starch/EPMA blends were extruded through a cylindrical tube viscometer with a half entry angle of 37.5°. For the blends, data could be obtained at low to moderate shear rates (10< _app<200s^–1). At higher shear rates, blends exhibited slip and/or degradation of starch. The viscosity of the blends exhibited shear-thinning properties. Regrinding and re-extruding through the viscometer a second time showed a significant reduction in shear viscosity for starch/SMA blends. Gel permeation chromatography data indicated that starch macromolecules degraded upon successive extrusion. Extensional viscosity, as estimated from entrance pressure drop method for starch/EPMA blends showed stretch thinning properties. Regrinding and re-extruding showed that the samples were more sensitive to changes in extensional viscosity as observed from the Trouton ratio versus extension rate plot. Optical microscopy showed the presence of starch granules after melt blending, the size of which was related to the torque (or stress) generated during extrusion. The higher the torque, the smaller the size of the starch granules. Successive extrusion runs reduced the number of unmelted granules.Nomenclature A,B Constants associated with power law fluids (Pa s^{m or n}) - e Entrance correction - H Height of slit die (m) - m, n Flow behavior index in shear and extension flow respectively - P _s Shear component of the entrance pressure drop (Pa) - P _e Extensional component of the entrance pressure drop (Pa) - Q volumetric flow rate (m³S^–1) - R _o radius of barrel exit (m) - R ₁ radius of cylindrical die (m) - T _r Trouton ratio - w width of slit die (m) - pressure gradient (Pam^–1) - half die entry angle - P _en Entrance Pressure Drop (Pa) - apparent extension rate (s^–1) - apparent shear rate (s^–1) - _w wall shear stress (Pa) - first normal stress difference in uniaxial extension (Pa)     

NMR relaxometry evaluation of nanostructured starch-PLA blends

Blends formed by starch and poly(lactic acid) (PLA) are very promising from environmental and economic standpoints, because starch is an abundant and cheap natural polymer and PLA is a biodegradable polymer that has good mechanical properties. In this study, starch-PLA blends were prepared by solution casting, employing chloroform and distilled water as a solvent pair. Then, dispersions containing 1, 3 and 5% montmorillonite clay and a dispersion containing 0.1% silica were added to the starch-PLA blends. The new materials obtained were characterized by X-ray diffraction, thermal analysis and, especially, nuclear low-field nuclear magnetic resonance (LF-NMR) relaxometry to measure the proton spin-lattice relaxation. All blends composed of starch and PLA showed significant increase in relaxation time due to the homogenous mixing of both polymers as a consequence of strong intermolecular interaction between them. Addition of clays caused substantial modification of the material and a large unique domain was observed. As a consequence, the domains corresponding to pure polymers were not observed. With the addition of the clay NT25, intermediate degradation temperatures were observed at concentrations of 3 and 5%, compared to the degradation temperatures of pure polymers. The X-ray diffraction results indicated the formation of an intercalated nanocomposite. There was an increase in the organization of the material compared to previous results observed for polymeric material, indicating the formation of an intercalated structure.     

Purification and Characterization of a Hyperthermostable and High Maltogenic α-Amylase of an Extreme Thermophile <Emphasis Type="Italic">Geobacillus thermoleovorans</Emphasis>

The purified α-amylase of Geobacillus thermoleovorans had a molecular mass of 26 kDa with a pI of 5.4, and it was optimally active at 100 °C and pH 8.0. The T _1/2 of α-amylase at 100 °C increased from 3.6 to 5.6 h in the presence of cholic acid. The activation energy and temperature quotient (Q ₁₀) of the enzyme were 84.10 kJ/mol and 1.31, respectively. The activity of the enzyme was enhanced strongly by Co²⁺ and Fe²⁺; enhanced slightly by Ba²⁺, Mn²⁺, Ni²⁺, and Mg²⁺; inhibited strongly by Sn²⁺, Hg²⁺, and Pb²⁺, and inhibited slightly by EDTA, phenyl methyl sulfonyl fluoride, N-ethylmaleimide, and dithiothreitol. The enzyme activity was not affected by Ca²⁺ and ethylene glycol-bis (β-amino ethyl ether)-N,N,N,N-tetra acetic acid. Among different additives and detergents, polyethylene glycol 8000 and Tween 20, 40, and 80 stabilized the enzyme activity, whereas Triton X-100, glycerol, glycine, dextrin, and sodium dodecyl sulfate inhibited to a varied extent. α-Amylase exhibited activity on several starch substrates and their derivatives. The K _m and K _cat values (soluble starch) were 1.10 mg/ml and 5.9 × 10³ /min, respectively. The enzyme hydrolyzed raw starch of pearl millet (Pennisetum typhoides) efficiently.     

水溶性N-(2-羧基苯甲酰基)化壳聚糖的合成

壳聚糖(β-(1,4)-2-氨基-2-脱氧-D-葡聚糖)是甲壳素脱乙酰化反应生成的一种线性聚合物,无毒、可生物降解、并有良好的成膜性和生物相容性,近年来已在水处理、医药、食品、化妆品、农业等领域显示了其独特的应用价值。但是,因分子内和分子间氢键的作用,壳聚糖只能溶于酸和酸     

阴离子型淀粉微球的合成及性能研究

本文以淀粉或淀粉衍生物为原料，ＰＯＣｌ３为交联剂，采用逆相悬浮交聚合技术合成了阴离子淀粉微球。以淀粉为基质中性微球不原料，用Ｎａ３Ｐ３Ｏ９作交联剂进行二次交联和阴离子化，得到另一种阴离子型淀粉微球，研究了两种微球的表观形态，粒径分布、溶胀性和吸附载药性能。